B <- 4. Definitions -> D
C
$ C field
(D) See: Compartments field.
$ C1 or C2 computer system
(O) /TCSEC/ See: Tutorial under "Trusted Computer System
Evaluation Criteria".
$ CA
(I) See: certification authority.
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$ CA certificate
(D) "A [digital] certificate for one CA issued by another CA."
[X509]
Deprecated Definition: IDOCs SHOULD NOT use the term with this
definition; the definition is ambiguous with regard to how the
certificate is constructed and how it is intended to be used.
IDOCs that use this term SHOULD provide a technical definition for
it. (See: certificate profile.)
Tutorial: There is no single, obvious choice for a technical
definition of this term. Different PKIs can use different
certificate profiles, and X.509 provides several choices of how to
issue certificates to CAs. For example, one possible definition is
the following: A v3 X.509 public-key certificate that has a
"basicConstraints" extension containing a "cA" value of "TRUE".
That would specifically indicate that "the certified public key
may be used to verify certificate signatures", i.e., that the
private key may be used by a CA.
However, there also are other ways to indicate such usage. The
certificate may have a "key Usage" extension that indicates the
purposes for which the public key may be used, and one of the
values that X.509 defines for that extension is "keyCertSign", to
indicate that the certificate may be used for verifying a CA's
signature on certificates. If "keyCertSign" is present in a
certificate that also has a "basicConstraints" extension, then
"cA" is set to "TRUE" in that extension. Alternatively, a CA could
be issued a certificate in which "keyCertSign" is asserted without
"basicConstraints" being present; and an entity that acts as a CA
could be issued a certificate with "keyUsage" set to other values,
either with or without "keyCertSign".
$ CA domain
(N) /PKI/ A security policy domain that "consists of a CA and its
subjects [i.e., the entities named in the certificates issued by
the CA]. Sometimes referred to as a PKI domain." [PAG] (See:
domain.)
$ Caesar cipher
(I) A cipher that is defined for an alphabet of N characters,
A(1), A(2), ..., A(N), and creates cipher text by replacing each
plaintext character A(i) by A(i+K, mod N) for some 0<K<N+1. [Schn]
Examples: (a) During the Gallic wars, Julius Caesar used a cipher
with K=3. In a Caesar cipher with K=3 for the English alphabet, A
is replaced by D, B by E, C by F, ..., W by Z, X by A, Y by B, Z
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by C. (b) UNIX systems sometimes include "ROT13" software that
implements a Caesar cipher with K=13 (i.e., ROTate by 13).
$ call back
(I) An authentication technique for terminals that remotely access
a computer via telephone lines; the host system disconnects the
caller and then reconnects on a telephone number that was
previously authorized for that terminal.
$ CAM
(O) See: Certificate Arbitrator Module.
$ CANEWARE
(O) An end-to-end encryption system for computer data networks
that was developed by the U.S. DoD in the 1980s to provide host-
to-host data confidentiality service for datagrams in OSIRM Layer
3. [Roge] (Compare: BLACKER, IPsec.)
Tutorial: Each user host connects to its own bump-in-the-wire
encryption device called a CANEWARE Front End (CFE), through which
the host connects to the subnetwork. CANEWARE uses symmetric
encryption for CFE-to-CFE traffic, but also uses FIREFLY to
establish those session keys. The public-key certificates issued
by the FIREFLY system include credentials for mandatory access
control. For discretionary access control, the system also
includes one or more centralized CANEWARE Control Processors
(CCPs) that connect to the subnetwork, maintain a database for
discretionary access control authorizations, and communicate those
authorizations to assigned sets of CFEs.
The CANEWARE system is MLS in only two of the three ways that
BLACKER is MLS: (a) Like BLACKER BFEs, CFEs form a security
perimeter around a subnetwork, separating user hosts from the
subnetwork, so that the subnetwork can operate at a different
security level than the hosts. (b) Like BLACKER, the CANEWARE
components are trusted to separate datagrams of different security
levels, so that each datagram of a given security level can be
received only by a host that is authorized for that security
level; and thus CANEWARE can separate host communities that
operate at different security levels. (c) Unlike a BFE, the host
side of a CFE is not MLS, and treats all packets received from a
user host as being at the same mandatory security level.
$ capability list
(I) /information system/ A mechanism that implements access
control for a system entity by enumerating the system resources
that the entity is permitted to access and, either implicitly or
explicitly, the access modes granted for each resource. (Compare:
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access control list, access control matrix, access profile,
capability token.)
$ capability token
(I) A token (usually an unforgeable data object) that gives the
bearer or holder the right to access a system resource. Possession
of the token is accepted by a system as proof that the holder has
been authorized to access the resource indicated by the token.
(See: attribute certificate, capability list, credential, digital
certificate, ticket, token.)
$ Capability Maturity Model (CMM)
(N) Method for judging the maturity of software processes in an
organization and for identifying crucial practices needed to
increase process maturity. [Chris] (Compare: Common Criteria.)
Tutorial: The CMM does not specify security evaluation criteria
(see: assurance level), but its use may improve security
assurance. The CMM describes principles and practices that can
improve software processes in terms of evolving from ad hoc
processes to disciplined processes. The CMM has five levels:
- Initial: Software processes are ad hoc or chaotic, and few are
well-defined. Success depends on individual effort and heroics.
- Repeatable: Basic project management processes are established
to track cost, schedule, and functionality. Necessary process
discipline is in place to repeat earlier successes on projects
with similar applications.
- Defined: Software process for both management and engineering
activities is documented, standardized, and integrated into a
standard software process for the organization. Each project
uses an approved, tailored version of the organization's
standard process for developing and maintaining software.
- Managed: Detailed measures of software process and product
quality are collected. Both software process and products are
quantitatively understood and controlled.
- Optimizing: Continuous process improvement is enabled by
quantitative feedback from the process and from piloting
innovative ideas and technologies.
$ CAPI
(I) See: cryptographic application programming interface.
$ CAPSTONE
(N) An integrated microcircuit (in MYK-8x series manufactured by
Mykotronx, Inc.) that implements SKIPJACK, KEA, DSA, SHA, and
basic mathematical functions needed to support asymmetric
cryptography; has a non-deterministic random number generator; and
supports key escrow. (See: FORTEZZA. Compare: CLIPPER.)
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$ card
See: cryptographic card, FORTEZZA, payment card, PC card, smart
card, token.
$ card backup
See: token backup.
$ card copy
See: token copy.
$ card restore
See: token restore.
$ cardholder
1. (I) An entity to whom or to which a card has been issued.
Usage: Usually refers to a living human being, but might refer (a)
to a position (see: billet, role) in an organization or (b) to an
automated process. (Compare: user.)
2. (O) /SET/ "The holder of a valid payment card account and user
of software supporting electronic commerce." [SET2] A cardholder
is issued a payment card by an issuer. SET ensures that in the
cardholder's interactions with merchants, the payment card account
information remains confidential. [SET1]
$ cardholder certificate
(O) /SET/ A digital certificate that is issued to a cardholder
upon approval of the cardholder's issuing financial institution
and that is transmitted to merchants with purchase requests and
encrypted payment instructions, carrying assurance that the
account number has been validated by the issuing financial
institution and cannot be altered by a third party. [SET1]
$ cardholder certification authority (CCA)
(O) /SET/ A CA responsible for issuing digital certificates to
cardholders and operated on behalf of a payment card brand, an
issuer, or another party according to brand rules. A CCA maintains
relationships with card issuers to allow for the verification of
cardholder accounts. A CCA does not issue a CRL but does
distribute CRLs issued by root CAs, brand CAs, geopolitical CAs,
and payment gateway CAs. [SET2]
$ CAST
(N) A design procedure for symmetric encryption algorithms, and a
resulting family of algorithms, invented by Carlisle Adams (C.A.)
and Stafford Tavares (S.T.). [R2144, R2612]
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$ category
(I) A grouping of sensitive information items to which a non-
hierarchical restrictive security label is applied to increase
protection of the data. (See: formal access approval. Compare:
compartment, classification.)
$ CAW
(N) See: certification authority workstation.
$ CBC
(N) See: cipher block chaining.
$ CCA
(O) See: cardholder certification authority.
$ CCEP
(O) See: Commercial COMSEC Endorsement Program.
$ CCI
(O) See: Controlled Cryptographic Item.
$ CCITT
(N) Acronym for French translation of International Telephone and
Telegraph Consultative Committee. Now renamed ITU-T.
$ CCM
(N) See: Counter with Cipher Block Chaining-Message Authentication
Code.
$ CERIAS
(O) Purdue University's Center for Education and Research in
Information Assurance and Security, which includes faculty from
multiple schools and departments and takes a multidisciplinary
approach to security problems ranging from technical to ethical,
legal, educational, communicational, linguistic, and economic.
$ CERT
(I) See: computer emergency response team.
$ certificate
1. (I) /general English/ A document that attests to the truth of
something or the ownership of something.
2. (I) /general security/ See: capability token, digital
certificate.
3. (I) /PKI/ See: attribute certificate, public-key certificate.
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$ Certificate Arbitrator Module (CAM)
(O) An open-source software module that is designed to be
integrated with an application for routing, replying to, and
otherwise managing and meditating certificate validation requests
between that application and the CAs in the ACES PKI.
$ certificate authority
(D) Synonym for "certification authority".
Deprecated Term: IDOCs SHOULD NOT use this term; it suggests
careless use of the term "certification authority", which is
preferred in PKI standards (e.g., [X509, R3280]).
$ certificate chain
(D) Synonym for "certification path". (See: trust chain.)
Deprecated Term: IDOCs SHOULD NOT use this term; it duplicates the
meaning of a standardized term. Instead, use "certification path".
$ certificate chain validation
(D) Synonym for "certificate validation" or "path validation".
Deprecated Term: IDOCs SHOULD NOT use this term; it duplicates the
meaning of standardized terms and mixes concepts in a potentially
misleading way. Instead, use "certificate validation" or "path
validation", depending on what is meant. (See: validate vs.
verify.)
$ certificate creation
(I) The act or process by which a CA sets the values of a digital
certificate's data fields and signs it. (See: issue.)
$ certificate expiration
(I) The event that occurs when a certificate ceases to be valid
because its assigned lifetime has been exceeded. (See: certificate
revocation, expire.)
Tutorial: The assigned lifetime of an X.509 certificate is stated
in the certificate itself. (See: validity period.)
$ certificate extension
(I) See: extension.
$ certificate holder
(D) Synonym for the "subject" of a digital certificate. (Compare:
certificate owner, certificate user.)
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Deprecated Definition: IDOCs SHOULD NOT use this term as a synonym
for the subject of a digital certificate; the term is potentially
ambiguous. For example, the term could be misunderstood as
referring to a system entity or component, such as a repository,
that simply has possession of a copy of the certificate.
$ certificate management
(I) The functions that a CA may perform during the lifecycle of a
digital certificate, including the following:
- Acquire and verify data items to bind into the certificate.
- Encode and sign the certificate.
- Store the certificate in a directory or repository.
- Renew, rekey, and update the certificate.
- Revoke the certificate and issue a CRL.
(See: archive management, certificate management, key management,
security architecture, token management.)
$ certificate management authority (CMA)
(D) /U.S. DoD/ Used to mean either a CA or an RA. [DoD7, SP32]
Deprecated Term: IDOCs SHOULD NOT use this term because it is
potentially ambiguous, such as in a context involving ICRLs.
Instead, use CA, RA, or both, depending on what is meant.
$ certificate owner
(D) Synonym for the "subject" of a digital certificate. (Compare:
certificate holder, certificate user.)
Deprecated Definition: IDOCs SHOULD NOT use this term as a synonym
for the subject of a digital certificate; the term is potentially
ambiguous. For example, the term could refer to a system entity,
such as a corporation, that has purchased a certificate to operate
equipment, such as a Web server.
$ certificate path
(D) Synonym for "certification path".
Deprecated Term: IDOCs SHOULD NOT use this term; it suggests
careless use of "certification path", which is preferred in PKI
standards (e.g., [X509, R3280]).
$ certificate policy
(I) "A named set of rules that indicates the applicability of a
certificate to a particular community and/or class of application
with common security requirements." [X509] (Compare: CPS, security
policy.)
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Example: U.S. DoD's certificate policy [DoD7] defined four classes
(i.e., assurance levels) for X.509 public-key certificates and
defines the applicability of those classes. (See: class 2.)
Tutorial: A certificate policy can help a certificate user to
decide whether a certificate should be trusted in a particular
application. "For example, a particular certificate policy might
indicate applicability of a type of certificate for the
authentication of electronic data interchange transactions for the
trading of goods within a given price range." [R3647]
A v3 X.509 public-key certificate may have a "certificatePolicies"
extension that lists certificate policies, recognized by the
issuing CA, that apply to the certificate and govern its use. Each
policy is denoted by an object identifier and may optionally have
certificate policy qualifiers. (See: certificate profile.)
Each SET certificate specifies at least one certificate policy,
that of the SET root CA. SET uses certificate policy qualifiers to
point to the actual policy statement and to add qualifying
policies to the root policy. (See: SET qualifier.)
$ certificate policy qualifier
(I) Information that pertains to a certificate policy and is
included in a "certificatePolicies" extension in a v3 X.509
public-key certificate.
$ certificate profile
(I) A specification (e.g., [DoD7, R3280]) of the format and
semantics of public-key certificates or attribute certificates,
constructed for use in a specific application context by selecting
from among options offered by a broader standard. (Compare:
protection profile.)
$ certificate reactivation
(I) The act or process by which a digital certificate, that a CA
has designated for revocation but not yet listed on a CRL, is
returned to the valid state.
$ certificate rekey
1. (I) The act or process by which an existing public-key
certificate has its key value changed by issuing a new certificate
with a different (usually new) public key. (See: certificate
renewal, certificate update, rekey.)
Tutorial: For an X.509 public-key certificate, the essence of
rekey is that the subject stays the same and a new public key is
bound to that subject. Other changes are made, and the old
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certificate is revoked, only as required by the PKI and CPS in
support of the rekey. If changes go beyond that, the process is a
"certificate update".
2. (O) /MISSI/ The act or process by which a MISSI CA creates a
new X.509 public-key certificate that is identical to the old one,
except the new one has (a) a new, different KEA key or (b) a new,
different DSS key or (c) new, different KEA and DSS keys. The new
certificate also has a different serial number and may have a
different validity period. A new key creation date and maximum key
lifetime period are assigned to each newly generated key. If a new
KEA key is generated, that key is assigned a new KMID. The old
certificate remains valid until it expires, but may not be further
renewed, rekeyed, or updated.
$ certificate renewal
(I) The act or process by which the validity of the binding
asserted by an existing public-key certificate is extended in time
by issuing a new certificate. (See: certificate rekey, certificate
update.)
Tutorial: For an X.509 public-key certificate, this term means
that the validity period is extended (and, of course, a new serial
number is assigned) but the binding of the public key to the
subject and to other data items stays the same. The other data
items are changed, and the old certificate is revoked, only as
required by the PKI and CPS to support the renewal. If changes go
beyond that, the process is a "certificate rekey" or "certificate
update".
$ certificate request
(D) Synonym for "certification request".
Deprecated Term: IDOCs SHOULD NOT use this term; it suggests
careless use of the term "certification request", which is
preferred in PKI standards (e.g., see PKCS #10).
$ certificate revocation
(I) The event that occurs when a CA declares that a previously
valid digital certificate issued by that CA has become invalid;
usually stated with an effective date.
Tutorial: In X.509, a revocation is announced to potential
certificate users by issuing a CRL that mentions the certificate.
Revocation and listing on a CRL is only necessary prior to the
certificate's scheduled expiration.
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$ certificate revocation list (CRL)
1. (I) A data structure that enumerates digital certificates that
have been invalidated by their issuer prior to when they were
scheduled to expire. (See: certificate expiration, delta CRL,
X.509 certificate revocation list.)
2. (O) "A signed list indicating a set of certificates that are no
longer considered valid by the certificate issuer. In addition to
the generic term CRL, some specific CRL types are defined for CRLs
that cover particular scopes." [X509]
$ certificate revocation tree
(N) A mechanism for distributing notices of certificate
revocations; uses a tree of hash results that is signed by the
tree's issuer. Offers an alternative to issuing a CRL, but is not
supported in X.509. (See: certificate status responder.)
$ certificate serial number
1. (I) An integer value that (a) is associated with, and may be
carried in, a digital certificate; (b) is assigned to the
certificate by the certificate's issuer; and (c) is unique among
all the certificates produced by that issuer.
2. (O) "An integer value, unique within the issuing CA, [that] is
unambiguously associated with a certificate issued by that CA."
[X509]
$ certificate status authority
(D) /U.S. DoD/ "A trusted entity that provides on-line
verification to a Relying Party of a subject certificate's
trustworthiness [should instead say 'validity'], and may also
provide additional attribute information for the subject
certificate." [DoD7]
Deprecated Term: IDOCs SHOULD NOT use this term because it is not
widely accepted; instead, use "certificate status responder" or
"OCSP server", or otherwise explain what is meant.
$ certificate status responder
(N) /FPKI/ A trusted online server that acts for a CA to provide
authenticated certificate status information to certificate users
[FPKI]. Offers an alternative to issuing a CR. (See: certificate
revocation tree, OCSP.)
$ certificate update
(I) The act or process by which non-key data items bound in an
existing public-key certificate, especially authorizations granted
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to the subject, are changed by issuing a new certificate. (See:
certificate rekey, certificate renewal.)
Usage: For an X.509 public-key certificate, the essence of this
process is that fundamental changes are made in the data that is
bound to the public key, such that it is necessary to revoke the
old certificate. (Otherwise, the process is only a "certificate
rekey" or "certificate renewal".)
$ certificate user
1. (I) A system entity that depends on the validity of information
(such as another entity's public key value) provided by a digital
certificate. (See: relying party. Compare: /digital certificate/
subject.)
Usage: The depending entity may be a human being or an
organization, or a device or process controlled by a human or
organization. (See: user.)
2. (O) "An entity that needs to know, with certainty, the public
key of another entity." [X509]
3. (D) Synonym for "subject" of a digital certificate.
Deprecated Definition: IDOCs SHOULD NOT use this term with
definition 3; the term could be confused with one of the other two
definitions given above.
$ certificate validation
1. (I) An act or process by which a certificate user establishes
that the assertions made by a digital certificate can be trusted.
(See: valid certificate, validate vs. verify.)
2. (O) "The process of ensuring that a certificate was valid at a
given time, including possibly the construction and processing of
a certification path [R4158], and ensuring that all certificates
in that path were valid (i.e. were not expired or revoked) at that
given time." [X509]
Tutorial: To validate a certificate, a certificate user checks
that the certificate is properly formed and signed and is
currently in force:
- Checks the syntax and semantics: Parses the certificate's
syntax and interprets its semantics, applying rules specified
for and by its data fields, such as for critical extensions in
an X.509 certificate.
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- Checks the signature: Uses the issuer's public key to verify
the digital signature of the CA who issued the certificate in
question. If the verifier obtains the issuer's public key from
the issuer's own public-key certificate, that certificate
should be validated, too. That validation may lead to yet
another certificate to be validated, and so on. Thus, in
general, certificate validation involves discovering and
validating a certification path.
- Checks currency and revocation: Verifies that the certificate
is currently in force by checking that the current date and
time are within the validity period (if that is specified in
the certificate) and that the certificate is not listed on a
CRL or otherwise announced as invalid. (The CRLs also must be
checked by a similar validation process.)
$ certification
1. (I) /information system/ Comprehensive evaluation (usually made
in support of an accreditation action) of an information system's
technical security features and other safeguards to establish the
extent to which the system's design and implementation meet a set
of specified security requirements. [C4009, FP102, SP37] (See:
accreditation. Compare: evaluation.)
2. (I) /digital certificate/ The act or process of vouching for
the truth and accuracy of the binding between data items in a
certificate. (See: certify.)
3. (I) /PKI/ The act or process of vouching for the ownership of a
public key by issuing a public-key certificate that binds the key
to the name of the entity that possesses the matching private key.
Besides binding a key with a name, a public-key certificate may
bind those items with other restrictive or explanatory data items.
(See: X.509 public-key certificate.)
4. (O) /SET/ "The process of ascertaining that a set of
requirements or criteria has been fulfilled and attesting to that
fact to others, usually with some written instrument. A system
that has been inspected and evaluated as fully compliant with the
SET protocol by duly authorized parties and process would be said
to have been certified compliant." [SET2]
$ certification authority (CA)
1. (I) An entity that issues digital certificates (especially
X.509 certificates) and vouches for the binding between the data
items in a certificate.
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2. (O) "An authority trusted by one or more users to create and
assign certificates. Optionally the certification authority may
create the user's keys." [X509]
Tutorial: Certificate users depend on the validity of information
provided by a certificate. Thus, a CA should be someone that
certificate users trust and that usually holds an official
position created and granted power by a government, a corporation,
or some other organization. A CA is responsible for managing the
life cycle of certificates (see: certificate management) and,
depending on the type of certificate and the CPS that applies, may
be responsible for the lifecycle of key pairs associated with the
certificates (see: key management).
$ certification authority workstation (CAW)
(N) A computer system that enables a CA to issue digital
certificates and supports other certificate management functions
as required.
$ certification hierarchy
1. (I) A tree-structured (loop-free) topology of relationships
between CAs and the entities to whom the CAs issue public-key
certificates. (See: hierarchical PKI, hierarchy management.)
Tutorial: In this structure, one CA is the top CA, the highest
level of the hierarchy. (See: root, top CA.) The top CA may issue
public-key certificates to one or more additional CAs that form
the second-highest level. Each of these CAs may issue certificates
to more CAs at the third-highest level, and so on. The CAs at the
second-lowest level issue certificates only to non-CA entities
that form the lowest level (see: end entity). Thus, all
certification paths begin at the top CA and descend through zero
or more levels of other CAs. All certificate users base path
validations on the top CA's public key.
2. (I) /PEM/ A certification hierarchy for PEM has three levels of
CAs [R1422]:
- The highest level is the "Internet Policy Registration
Authority".
- A CA at the second-highest level is a "policy certification
authority".
- A CA at the third-highest level is a "certification authority".
3. (O) /MISSI/ A certification hierarchy for MISSI has three or
four levels of CAs:
- A CA at the highest level, the top CA, is a "policy approving
authority".
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- A CA at the second-highest level is a "policy creation
authority".
- A CA at the third-highest level is a local authority called a
"certification authority".
- A CA at the fourth-highest (optional) level is a "subordinate
certification authority".
4. (O) /SET/ A certification hierarchy for SET has three or four
levels of CAs:
- The highest level is a "SET root CA".
- A CA at the second-highest level is a "brand certification
authority".
- A CA at the third-highest (optional) level is a "geopolitical
certification authority".
- A CA at the fourth-highest level is a "cardholder CA", a
"merchant CA", or a "payment gateway CA".
$ certification path
1. (I) A linked sequence of one or more public-key certificates,
or one or more public-key certificates and one attribute
certificate, that enables a certificate user to verify the
signature on the last certificate in the path, and thus enables
the user to obtain (from that last certificate) a certified public
key, or certified attributes, of the system entity that is the
subject of that last certificate. (See: trust anchor, certificate
validation, valid certificate.)
2. (O) "An ordered sequence of certificates of objects in the
[X.500 Directory Information Tree] which, together with the public
key of the initial object in the path, can be processed to obtain
that of the final object in the path." [R3647, X509]
Tutorial: The list is "linked" in the sense that the digital
signature of each certificate (except possibly the first) is
verified by the public key contained in the preceding certificate;
i.e., the private key used to sign a certificate and the public
key contained in the preceding certificate form a key pair that
has previously been bound to the authority that signed.
The path is the "list of certificates needed to [enable] a
particular user to obtain the public key [or attributes] of
another [user]." [X509] Here, the word "particular" points out
that a certification path that can be validated by one certificate
user might not be able to be validated by another. That is because
either the first certificate needs to be a trusted certificate or
the signature on the first certificate needs to be verifiable by a
trusted key (e.g., a root key), but such trust is established only
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relative to a "particular" (i.e., specific) user, not absolutely
for all users.
$ certification policy
(D) Synonym for either "certificate policy" or "certification
practice statement".
Deprecated Term: IDOCs SHOULD NOT use this term as a synonym for
either of those terms; that would be duplicative and would mix
concepts in a potentially misleading way. Instead, use either
"certificate policy" or "certification practice statement",
depending on what is meant.
$ certification practice statement (CPS)
(I) "A statement of the practices which a certification authority
employs in issuing certificates." [DSG, R3647] (See: certificate
policy.)
Tutorial: A CPS is a published security policy that can help a
certificate user to decide whether a certificate issued by a
particular CA can be trusted enough to use in a particular
application. A CPS may be (a) a declaration by a CA of the details
of the system and practices it uses in its certificate management
operations, (b) part of a contract between the CA and an entity to
whom a certificate is issued, (c) a statute or regulation
applicable to the CA, or (d) a combination of these types
involving multiple documents. [DSG]
A CPS is usually more detailed and procedurally oriented than a
certificate policy. A CPS applies to a particular CA or CA
community, while a certificate policy applies across CAs or
communities. A CA with its single CPS may support multiple
certificate policies, which may be used for different application
purposes or by different user communities. On the other hand,
multiple CAs, each with a different CPS, may support the same
certificate policy. [R3647]
$ certification request
(I) An algorithm-independent transaction format (e.g., PKCS #10,
RFC 4211) that contains a DN, and a public key or, optionally, a
set of attributes, collectively signed by the entity requesting
certification, and sent to a CA, which transforms the request to
an X.509 public-key certificate or another type of certificate.
$ certify
1. (I) Issue a digital certificate and thus vouch for the truth,
accuracy, and binding between data items in the certificate (e.g.,
"X.509 public-key certificate"), such as the identity of the
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certificate's subject and the ownership of a public key. (See:
certification.)
Usage: To "certify a public key" means to issue a public-key
certificate that vouches for the binding between the certificate's
subject and the key.
2. (I) The act by which a CA uses measures to verify the truth,
accuracy, and binding between data items in a digital certificate.
Tutorial: A description of the measures used for verification
should be included in the CA's CPS.
$ CFB
(N) See: cipher feedback.
$ chain
(D) See: trust chain.
$ Challenge Handshake Authentication Protocol (CHAP)
(I) A peer entity authentication method (employed by PPP and other
protocols, e.g., RFC 3720) that uses a randomly generated
challenge and requires a matching response that depends on a
cryptographic hash of some combination of the challenge and a
secret key. [R1994] (See: challenge-response, PAP.)
$ challenge-response
(I) An authentication process that verifies an identity by
requiring correct authentication information to be provided in
response to a challenge. In a computer system, the authentication
information is usually a value that is required to be computed in
response to an unpredictable challenge value, but it might be just
a password.
$ Challenge-Response Authentication Mechanism (CRAM)
(I) /IMAP4/ A mechanism [R2195], intended for use with IMAP4
AUTHENTICATE, by which an IMAP4 client uses a keyed hash [R2104]
to authenticate itself to an IMAP4 server. (See: POP3 APOP.)
Tutorial: The server includes a unique time stamp in its ready
response to the client. The client replies with the client's name
and the hash result of applying MD5 to a string formed from
concatenating the time stamp with a shared secret that is known
only to the client and the server.
$ channel
1. (I) An information transfer path within a system. (See: covert
channel.)
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2. (O) "A subdivision of the physical medium allowing possibly
shared independent uses of the medium." (RFC 3753)
$ channel capacity
(I) The total capacity of a link to carry information; usually
expressed in bits per second. (RFC 3753) (Compare: bandwidth.)
Tutorial: Within a given bandwidth, the theoretical maximum
channel capacity is given by Shannon's Law. The actual channel
capacity is determined by the bandwidth, the coding system used,
and the signal-to-noise ratio.
$ CHAP
(I) See: Challenge Handshake Authentication Protocol.
$ checksum
(I) A value that (a) is computed by a function that is dependent
on the contents of a data object and (b) is stored or transmitted
together with the object, for detecting changes in the data. (See:
cyclic redundancy check, data integrity service, error detection
code, hash, keyed hash, parity bit, protected checksum.)
Tutorial: To gain confidence that a data object has not been
changed, an entity that later uses the data can independently
recompute the checksum value and compare the result with the value
that was stored or transmitted with the object.
Computer systems and networks use checksums (and other mechanisms)
to detect accidental changes in data. However, active wiretapping
that changes data could also change an accompanying checksum to
match the changed data. Thus, some checksum functions by
themselves are not good countermeasures for active attacks. To
protect against active attacks, the checksum function needs to be
well-chosen (see: cryptographic hash), and the checksum result
needs to be cryptographically protected (see: digital signature,
keyed hash).
$ Chinese wall policy
(I) A security policy to prevent conflict of interest caused by an
entity (e.g., a consultant) interacting with competing firms.
(See: Brewer-Nash model.)
Tutorial: All information is categorized into mutually exclusive
conflict-of-interest classes I(1), I(2), ..., I(M), and each firm
F(1), F(2), ..., F(N) belongs to exactly one class. The policy
states that if a consultant has access to class I(i) information
from a firm in that class, then the consultant may not access
information from another firm in that same class, but may access
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information from another firm that is in a different class. Thus,
the policy creates a barrier to communication between firms that
are in the same conflict-of-interest class. Brewer and Nash
modeled enforcement of this policy [BN89], including dealing with
policy violations that could occur because two or more consultants
work for the same firm.
$ chosen-ciphertext attack
(I) A cryptanalysis technique in which the analyst tries to
determine the key from knowledge of plain text that corresponds to
cipher text selected (i.e., dictated) by the analyst.
$ chosen-plaintext attack
(I) A cryptanalysis technique in which the analyst tries to
determine the key from knowledge of cipher text that corresponds
to plain text selected (i.e., dictated) by the analyst.
$ CIAC
(O) See: Computer Incident Advisory Capability.
$ CIK
(N) See: cryptographic ignition key.
$ cipher
(I) A cryptographic algorithm for encryption and decryption.
$ cipher block chaining (CBC)
(N) A block cipher mode that enhances ECB mode by chaining
together blocks of cipher text it produces. [FP081] (See: block
cipher, [R1829], [R2405], [R2451], [SP38A].)
Tutorial: This mode operates by combining (exclusive OR-ing) the
algorithm's ciphertext output block with the next plaintext block
to form the next input block for the algorithm.
$ cipher feedback (CFB)
(N) A block cipher mode that enhances ECB mode by chaining
together the blocks of cipher text it produces and operating on
plaintext segments of variable length less than or equal to the
block length. [FP081] (See: block cipher, [SP38A].)
Tutorial: This mode operates by using the previously generated
ciphertext segment as the algorithm's input (i.e., by "feeding
back" the cipher text) to generate an output block, and then
combining (exclusive OR-ing) that output block with the next
plaintext segment (block length or less) to form the next
ciphertext segment.
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$ cipher text
1. (I) /noun/ Data that has been transformed by encryption so that
its semantic information content (i.e., its meaning) is no longer
intelligible or directly available. (See: ciphertext. Compare:
clear text, plain text.)
2. (O) "Data produced through the use of encipherment. The
semantic content of the resulting data is not available."
[I7498-2]
$ ciphertext
1. (O) /noun/ Synonym for "cipher text" [I7498-2].
2. (I) /adjective/ Referring to cipher text. Usage: Commonly used
instead of "cipher-text". (Compare: cleartext, plaintext.)
$ ciphertext auto-key (CTAK)
(D) "Cryptographic logic that uses previous cipher text to
generate a key stream." [C4009, A1523] (See: KAK.)
Deprecated Term: IDOCs SHOULD NOT use this term; it is neither
well-known nor precisely defined. Instead, use terms associated
with modes that are defined in standards, such as CBC, CFB, and
OFB.
$ ciphertext-only attack
(I) A cryptanalysis technique in which the analyst tries to
determine the key solely from knowledge of intercepted cipher text
(although the analyst may also know other clues, such as the
cryptographic algorithm, the language in which the plain text was
written, the subject matter of the plain text, and some probable
plaintext words.)
$ ciphony
(O) The process of encrypting audio information.
$ CIPSO
(I) See: Common IP Security Option.
$ CKL
(I) See: compromised key list.
$ Clark-Wilson model
(N) A security model [Clark] to maintain data integrity in the
commercial world. (Compare: Bell-LaPadula model.)
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$ class 2, 3, 4, 5
(O) /U.S. DoD/ Assurance levels for PKIs, and for X.509 public-key
certificates issued by a PKI. [DoD7] (See: "first law" under
"Courtney's laws".)
- "Class 2": Intended for applications handling unclassified,
low-value data in minimally or moderately protected
environments.
- "Class 3": Intended for applications handling unclassified,
medium-value data in moderately protected environments, or
handling unclassified or high-value data in highly protected
environments, and for discretionary access control of
classified data in highly protected environments.
- "Class 4": Intended for applications handling unclassified,
high-value data in minimally protected environments.
- "Class 5": Intended for applications handling classified data
in minimally protected environments, and for authentication of
material that would affect the security of classified systems.
The environments are defined as follows:
- "Highly protected environment": Networks that are protected
either with encryption devices approved by NSA for protection
of classified data or via physical isolation, and that are
certified for processing system-high classified data, where
exposure of unencrypted data is limited to U.S. citizens
holding appropriate security clearances.
- "Moderately protected environment":
-- Physically isolated unclassified, unencrypted networks in
which access is restricted based on legitimate need.
-- Networks protected by NSA-approved, type 1 encryption,
accessible by U.S.-authorized foreign nationals.
- "Minimally protected environments": Unencrypted networks
connected to either the Internet or NIPRNET, either directly or
via a firewall.
$ Class A1, B3, B2, B1, C2, or C1 computer system
(O) /TCSEC/ See: Tutorial under "Trusted Computer System
Evaluation Criteria".
$ classification
1. (I) A grouping of classified information to which a
hierarchical, restrictive security label is applied to increase
protection of the data from unauthorized disclosure. (See:
aggregation, classified, data confidentiality service. Compare:
category, compartment.)
2. (I) An authorized process by which information is determined to
be classified and assigned to a security level. (Compare:
declassification.)
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Usage: Usually understood to involve data confidentiality, but
IDOCs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
$ classification label
(I) A security label that tells the degree of harm that will
result from unauthorized disclosure of the labeled data, and may
also tell what countermeasures are required to be applied to
protect the data from unauthorized disclosure. Example: IPSO.
(See: classified, data confidentiality service. Compare: integrity
label.)
Usage: Usually understood to involve data confidentiality, but
IDOCs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
$ classification level
(I) A hierarchical level of protection (against unauthorized
disclosure) that is required to be applied to certain classified
data. (See: classified. Compare: security level.)
Usage: Usually understood to involve data confidentiality, but
IDOCs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
$ classified
1. (I) Refers to information (stored or conveyed, in any form)
that is formally required by a security policy to receive data
confidentiality service and to be marked with a security label
(which, in some cases, might be implicit) to indicate its
protected status. (See: classify, collateral information, SAP,
security level. Compare: unclassified.)
Usage: Usually understood to involve data confidentiality, but
IDOCs SHOULD make this clear when data also is sensitive in other
ways and SHOULD use other terms for those other sensitivity
concepts. (See: sensitive information, data integrity.)
Mainly used by national governments, especially by the military,
but the underlying concept also applies outside of governments.
2. (O) /U.S. Government/ "Information that has been determined
pursuant to Executive Order 12958 or any predecessor Order, or by
the Atomic Energy Act of 1954, as amended, to require protection
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against unauthorized disclosure and is marked to indicate its
classified status." [C4009]
$ classify
(I) To officially designate an information item or type of
information as being classified and assigned to a specific
security level. (See: classified, declassify, security level.)
$ clean system
(I) A computer system in which the operating system and
application system software and files have been freshly installed
from trusted software distribution media. (Compare: secure state.)
$ clear
(D) /verb/ Synonym for "erase". [C4009]
Deprecated Definition: IDOCs SHOULD NOT use the term with this
definition; that could be confused with "clear text" in which
information is directly recoverable.
$ clear text
1. (I) /noun/ Data in which the semantic information content
(i.e., the meaning) is intelligible or is directly available,
i.e., not encrypted. (See: cleartext, in the clear. Compare:
cipher text, plain text.)
2. (O) /noun/ "Intelligible data, the semantic content of which is
available." [I7498-2]
3. (D) /noun/ Synonym for "plain text".
Deprecated Definition: IDOCs SHOULD NOT use this term as a synonym
for "plain text", because the plain text that is input to an
encryption operation may itself be cipher text that was output
from a previous encryption operation. (See: superencryption.)
$ clearance
See: security clearance.
$ clearance level
(I) The security level of information to which a security
clearance authorizes a person to have access.
$ cleartext
1. (O) /noun/ Synonym for "clear text" [I7498-2].
2. (I) /adjective/ Referring to clear text. Usage: Commonly used
instead of "clear-text". (Compare: ciphertext, plaintext.)
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3. (D) /adjective/ Synonym for "plaintext".
Deprecated Definition: IDOCs SHOULD NOT use this term as a synonym
for "plaintext", because the plaintext data that is input to an
encryption operation may itself be ciphertext data that was output
from a previous encryption operation. (See: superencryption.)
$ CLEF
(N) See: commercially licensed evaluation facility.
$ client
(I) A system entity that requests and uses a service provided by
another system entity, called a "server". (See: server.)
Tutorial: Usually, it is understood that the client and server are
automated components of the system, and the client makes the
request on behalf of a human user. In some cases, the server may
itself be a client of some other server.
$ client-server system
(I) A distributed system in which one or more entities, called
clients, request a specific service from one or more other
entities, called servers, that provide the service to the clients.
Example: The Word Wide Web, in which component servers provide
information that is requested by component clients called
"browsers".
$ CLIPPER
(N) An integrated microcircuit (in MYK-7x series manufactured by
Mykotronx, Inc.) that implements SKIPJACK, has a non-deterministic
random number generator, and supports key escrow. (See: Escrowed
Encryption Standard. Compare: CLIPPER.)
Tutorial: The chip was mainly intended for protecting
telecommunications over the public switched network. The key
escrow scheme for the chip involves a SKIPJACK key that is common
to all chips and that protects the unique serial number of the
chip, and a second SKIPJACK key unique to the chip that protects
all data encrypted by the chip. The second key is escrowed as
split key components held by NIST and the U.S. Treasury
Department.
$ closed security environment
(O) /U.S. DoD/ A system environment that meets both of the
following conditions: (a) Application developers (including
maintainers) have sufficient clearances and authorizations to
provide an acceptable presumption that they have not introduced
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malicious logic. (b) Configuration control provides sufficient
assurance that system applications and the equipment they run on
are protected against the introduction of malicious logic prior to
and during the operation of applications. [NCS04] (See: "first
law" under "Courtney's laws". Compare: open security environment.)
$ CMA
(D) See: certificate management authority.
$ CMAC
(N) A message authentication code [SP38B] that is based on a
symmetric block cipher. (See: block cipher.)
Derivation: Cipher-based MAC. (Compare: HMAC.)
Tutorial: Because CMAC is based on approved, symmetric-key block
ciphers, such as AES, CMAC can be considered a mode of operation
for those block ciphers. (See: mode of operation.)
$ CMCS
(O) See: COMSEC Material Control System.
$ CMM
(N) See: Capability Maturity Model.
$ CMS
(I) See: Cryptographic Message Syntax.
$ code
1. (I) A system of symbols used to represent information, which
might originally have some other representation. Examples: ASCII,
BER, country code, Morse code. (See: encode, object code, source
code.)
Deprecated Abbreviation: To avoid confusion with definition 1,
IDOCs SHOULD NOT use "code" as an abbreviation of "country code",
"cyclic redundancy code", "Data Authentication Code", "error
detection code", or "Message Authentication Code". To avoid
misunderstanding, use the fully qualified term in these other
cases, at least at the point of first usage.
2. (I) /cryptography/ An encryption algorithm based on
substitution; i.e., a system for providing data confidentiality by
using arbitrary groups (called "code groups") of letters, numbers,
or symbols to represent units of plain text of varying length.
(See: codebook, cryptography.)
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Deprecated Usage: To avoid confusion with definition 1, IDOCs
SHOULD NOT use "code" as a synonym for any of the following terms:
(a) "cipher", "hash", or other words that mean "a cryptographic
algorithm"; (b) "cipher text"; or (c) "encrypt", "hash", or other
words that refer to applying a cryptographic algorithm.
3. (I) An algorithm based on substitution, but used to shorten
messages rather than to conceal their content.
4. (I) /computer programming/ To write computer software. (See:
object code, source code.)
Deprecated Abbreviation: To avoid confusion with definition 1,
IDOCs SHOULD NOT use "code" as an abbreviation of "object code" or
"source code". To avoid misunderstanding, use the fully qualified
term in these other cases, at least at the point of first usage.
$ code book
1. (I) Document containing a systematically arranged list of
plaintext units and their ciphertext equivalents. [C4009]
2. (I) An encryption algorithm that uses a word substitution
technique. [C4009] (See: code, ECB.)
$ code signing
(I) A security mechanism that uses a digital signature to provide
data integrity and data origin authentication for software that is
being distributed for use. (See: mobile code, trusted
distribution.)
Tutorial: In some cases, the signature on a software module may
imply some assertion that the signer makes about the software. For
example, a signature may imply that the software has been
designed, developed, or tested according to some criterion.
$ code word
(O) /U.S. Government/ A single word that is used as a security
label (usually applied to classified information) but which itself
has a classified meaning. (See: classified, /U.S. Government/
security label.)
$ COI
(I) See: community of interest.
$ cold start
(N) /cryptographic module/ A procedure for initially keying
cryptographic equipment. [C4009]
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$ collateral information
(O) /U.S. Government/ Information that is classified but is not
required to be protected by an SAP. (See: /U.S. Government/
classified.)
$ color change
(I) In a system being operated in periods-processing mode, the act
of purging all information from one processing period and then
changing over to the next processing period. (See: BLACK, RED.)
$ Commercial COMSEC Evaluation Program (CCEP)
(O) "Relationship between NSA and industry in which NSA provides
the COMSEC expertise (i.e., standards, algorithms, evaluations,
and guidance) and industry provides design, development, and
production capabilities to produce a type 1 or type 2 product."
[C4009]
$ commercially licensed evaluation facility (CLEF)
(N) An organization that has official approval to evaluate the
security of products and systems under the Common Criteria, ITSEC,
or some other standard. (Compare: KLIF.)
$ Committee on National Security Systems (CNSS)
(O) /U.S. Government/ A Government, interagency, standing
committee of the President's Critical Infrastructure Protection
Board. The CNSS is chaired by the Secretary of Defense and
provides a forum for the discussion of policy issues, sets
national policy, and promulgates direction, operational
procedures, and guidance for the security of national security
systems. The Secretary of Defense and the Director of Central
Intelligence are responsible for developing and overseeing the
implementation of Government-wide policies, principles, standards,
and guidelines for the security of systems that handle national
security information.
$ Common Criteria for Information Technology Security
(N) A standard for evaluating information technology (IT) products
and systems. It states requirements for security functions and for
assurance measures. [CCIB] (See: CLEF, EAL, packages, protection
profile, security target, TOE. Compare: CMM.)
Tutorial: Canada, France, Germany, the Netherlands, the United
Kingdom, and the United States (NIST and NSA) began developing
this standard in 1993, based on the European ITSEC, the Canadian
Trusted Computer Product Evaluation Criteria (CTCPEC), and the
U.S. "Federal Criteria for Information Technology Security" and
its precursor, the TCSEC. Work was done in cooperation with
ISO/IEC Joint Technical Committee 1 (Information Technology),
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Subcommittee 27 (Security Techniques), Working Group 3 (Security
Criteria). Version 2.0 of the Criteria has been issued as ISO's
International Standard 15408. The U.S. Government intends this
standard to supersede both the TCSEC and FIPS PUB 140. (See:
NIAP.)
The standard addresses data confidentiality, data integrity, and
availability and may apply to other aspects of security. It
focuses on threats to information arising from human activities,
malicious or otherwise, but may apply to non-human threats. It
applies to security measures implemented in hardware, firmware, or
software. It does not apply to (a) administrative security not
related directly to technical security, (b) technical physical
aspects of security such as electromagnetic emanation control, (c)
evaluation methodology or administrative and legal framework under
which the criteria may be applied, (d) procedures for use of
evaluation results, or (e) assessment of inherent qualities of
cryptographic algorithms.
Part 1, Introduction and General Model, defines general concepts
and principles of IT security evaluation; presents a general model
of evaluation; and defines constructs for expressing IT security
objectives, for selecting and defining IT security requirements,
and for writing high-level specifications for products and
systems.
Part 2, Security Functional Requirements, contains a catalog of
well-defined and well-understood functional requirement statements
that are intended to be used as a standard way of expressing the
security requirements for IT products and systems.
Part 3, Security Assurance Requirements, contains a catalog of
assurance components for use as a standard way of expressing such
requirements for IT products and systems, and defines evaluation
criteria for protection profiles and security targets.
$ Common IP Security Option (CIPSO)
(I) See: secondary definition under "IPSO".
$ common name
(N) A character string that (a) may be a part of the X.500 DN of a
Directory object ("commonName" attribute), (b) is a (possibly
ambiguous) name by which the object is commonly known in some
limited scope (such as an organization), and (c) conforms to the
naming conventions of the country or culture with which it is
associated. [X520] (See: "subject" and "issuer" under "X.509
public-key certificate".)
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Examples: "Dr. Albert Einstein", "The United Nations", and "12-th
Floor Laser Printer".
$ communications cover
(N) "Concealing or altering of characteristic communications
patterns to hide information that could be of value to an
adversary." [C4009] (See: operations security, traffic-flow
confidentiality, TRANSEC.)
$ communication security (COMSEC)
(I) Measures that implement and assure security services in a
communication system, particularly those that provide data
confidentiality and data integrity and that authenticate
communicating entities.
Usage: COMSEC is usually understood to include (a) cryptography
and its related algorithms and key management methods and
processes, devices that implement those algorithms and processes,
and the lifecycle management of the devices and keying material.
Also, COMSEC is sometimes more broadly understood as further
including (b) traffic-flow confidentiality, (c) TRANSEC, and (d)
steganography [Kahn]. (See: cryptology, signal security.)
$ community of interest (COI)
1. (I) A set of entities that operate under a common security
policy. (Compare: domain.)
2. (I) A set of entities that exchange information collaboratively
for some purpose.
$ community risk
(N) Probability that a particular vulnerability will be exploited
within an interacting population and adversely affect some members
of that population. [C4009] (See: Morris worm, risk.)
$ community string
(I) A community name in the form of an octet string that serves as
a cleartext password in SNMP version 1 (RFC 1157) and version 2
(RFC 1901). (See: password, Simple Network Management Protocol.)
Tutorial: The SNMPv1 and SNMPv2 protocols have been declared
"historic" and have been replaced by the more secure SNMPv3
standard (RFCs 3410-3418), which does not use cleartext passwords.
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$ compartment
1. (I) A grouping of sensitive information items that require
special access controls beyond those normally provided for the
basic classification level of the information. (See: compartmented
security mode. Compare: category, classification.)
Usage: The term is usually understood to include the special
handling procedures to be used for the information.
2. (I) Synonym for "category".
Deprecated Usage: This Glossary defines "category" with a slightly
narrower meaning than "compartment". That is, a security label is
assigned to a category because the data owner needs to handle the
data as a compartment. However, a compartment could receive
special protection in a system without being assigned a category
label.
$ compartmented security mode
(N) A mode of system operation wherein all users having access to
the system have the necessary security clearance for the single,
hierarchical classification level of all data handled by the
system, but some users do not have the clearance for a non-
hierarchical category of some data handled by the system. (See:
category, /system operation/ under "mode", protection level,
security clearance.)
Usage: Usually abbreviated as "compartmented mode". This term was
defined in U.S. Government policy on system accreditation. In this
mode, a system may handle (a) a single hierarchical classification
level and (b) multiple non-hierarchical categories within that
level.
$ Compartments field
(I) A 16-bit field (the "C field") that specifies compartment
values in the security option (option type 130) of version 4 IP's
datagram header format. The valid field values are assigned by the
U.S. Government, as specified in RFC 791.
Deprecated Abbreviation: IDOCs SHOULD NOT use the abbreviation "C
field"; the abbreviation is potentially ambiguous. Instead, use
"Compartments field".
$ component
See: system component.
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$ compression
(I) A process that encodes information in a way that minimizes the
number of resulting code symbols and thus reduces storage space or
transmission time.
Tutorial: A data compression algorithm may be "lossless", i.e.,
retain all information that was encoded in the data, so that
decompression can recover all the information; or an algorithm may
be "lossy". Text usually needs to be compressed losslessly, but
images are often compressed with lossy schemes.
Not all schemes that encode information losslessly for machine
processing are efficient in terms of minimizing the number of
output bits. For example, ASCII encoding is lossless, but ASCII
data can often be losslessly reencoded in fewer bits with other
schemes. These more efficient schemes take advantage of some sort
of inherent imbalance, redundancy, or repetition in the data, such
as by replacing a character string in which all characters are the
same by a shorter string consisting of only the single character
and a character count.
Lossless compression schemes cannot effectively reduce the number
of bits in cipher text produced by a strong encryption algorithm,
because the cipher text is essentially a pseudorandom bit string
that does not contain patterns susceptible to reencoding.
Therefore, protocols that offer both encryption and compression
services (e.g., SSL) need to perform the compression operation
before the encryption operation.
$ compromise
See: data compromise, security compromise.
$ compromise recovery
(I) The process of regaining a secure state for a system after
detecting that the system has experienced a security compromise.
$ compromised key list (CKL)
(N) /MISSI/ A list that identifies keys for which unauthorized
disclosure or alteration may have occurred. (See: compromise.)
Tutorial: A CKL is issued by a CA, like a CRL is issued. But a CKL
lists only KMIDs, not subjects that hold the keys, and not
certificates in which the keys are bound.
$ COMPUSEC
(I) See: computer security.
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$ computer emergency response team (CERT)
(I) An organization that studies computer and network INFOSEC in
order to provide incident response services to victims of attacks,
publish alerts concerning vulnerabilities and threats, and offer
other information to help improve computer and network security.
(See: CSIRT, security incident.)
Examples: CERT Coordination Center at Carnegie Mellon University
(sometimes called "the" CERT); CIAC.
$ Computer Incident Advisory Capability (CIAC)
(O) The centralized CSIRT of the U.S. Department of Energy; a
member of FIRST.
$ computer network
(I) A collection of host computers together with the subnetwork or
internetwork through which they can exchange data.
Usage: This definition is intended to cover systems of all sizes
and types, ranging from the complex Internet to a simple system
composed of a personal computer dialing in as a remote terminal of
another computer.
$ computer platform
(I) A combination of computer hardware and an operating system
(which may consist of software, firmware, or both) for that
hardware. (Compare: computer system.)
$ computer security (COMPUSEC)
1. (I) Measures to implement and assure security services in a
computer system, particularly those that assure access control
service.
Usage: Usually refers to internal controls (functions, features,
and technical characteristics) that are implemented in software
(especially in operating systems); sometimes refers to internal
controls implemented in hardware; rarely used to refer to external
controls.
2. (O) "The protection afforded to an automated information system
in order to attain the applicable objectives of preserving the
integrity, availability and confidentiality of information system
resources (includes hardware, software, firmware,
information/data, and telecommunications)." [SP12]
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$ computer security incident response team (CSIRT)
(I) An organization "that coordinates and supports the response to
security incidents that involve sites within a defined
constituency." [R2350] (See: CERT, FIRST, security incident.)
Tutorial: To be considered a CSIRT, an organization must do as
follows: (a) Provide a (secure) channel for receiving reports
about suspected security incidents. (b) Provide assistance to
members of its constituency in handling the incidents. (c)
Disseminate incident-related information to its constituency and
other involved parties.
$ computer security object
(I) The definition or representation of a resource, tool, or
mechanism used to maintain a condition of security in computerized
environments. Includes many items referred to in standards that
are either selected or defined by separate user communities.
[CSOR] (See: object identifier, Computer Security Objects
Register.)
$ Computer Security Objects Register (CSOR)
(N) A service operated by NIST is establishing a catalog for
computer security objects to provide stable object definitions
identified by unique names. The use of this register will enable
the unambiguous specification of security parameters and
algorithms to be used in secure data exchanges. (See: object
identifier.)
Tutorial: The CSOR follows registration guidelines established by
the international standards community and ANSI. Those guidelines
establish minimum responsibilities for registration authorities
and assign the top branches of an international registration
hierarchy. Under that international registration hierarchy, the
CSOR is responsible for the allocation of unique identifiers under
the branch: {joint-iso-ccitt(2) country(16) us(840)
organization(1) gov(101) csor(3)}.
$ computer system
(I) Synonym for "information system", or a component thereof.
(Compare: computer platform.)
$ Computers At Risk
(O) The 1991 report [NRC91] of the System Security Study
Committee, sponsored by the U.S. National Academy of Sciences and
supported by the Defense Advanced Research Projects Agency of the
U.S. DoD. It made many recommendations for industry and
governments to improve computer security and trustworthiness. Some
of the most important recommendations (e.g., establishing an
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Information Security Foundation chartered by the U.S. Government)
have not been implemented at all, and others (e.g., codifying
Generally Accepted System Security Principles similar to
accounting principles) have been implemented but not widely
adopted [SP14, SP27].
$ COMSEC
(I) See: communication security.
$ COMSEC account
(O) /U.S. Government/ "Administrative entity, identified by an
account number, used to maintain accountability, custody, and
control of COMSEC material." [C4009] (See: COMSEC custodian.)
$ COMSEC accounting
(O) /U.S. Government/ The process of creating, collecting, and
maintaining data records that describe the status and custody of
designated items of COMSEC material. (See: accounting legend
code.)
Tutorial: Almost any secure information system needs to record a
security audit trail, but a system that manages COMSEC material
needs to record additional data about the status and custody of
COMSEC items.
- COMSEC tracking: The process of automatically collecting,
recording, and managing information that describes the status
of designated items of COMSEC material at all times during each
product's lifecycle.
- COMSEC controlling: The process of supplementing tracking data
with custody data, which consists of explicit acknowledgements
of system entities that they (a) have received specific COMSEC
items and (b) are responsible for preventing exposure of those
items.
For example, a key management system that serves a large customer
base needs to record tracking data for the same reasons that a
national parcel delivery system does, i.e., to answer the question
"Where is that thing now?". If keys are encrypted immediately upon
generation and handled only in BLACK form between the point of
generation and the point of use, then tracking may be all that is
needed. However, in cases where keys are handled at least partly
in RED form and are potentially subject to exposure, then tracking
needs to be supplemented by controlling.
Data that is used purely for tracking need be retained only
temporarily, until an item's status changes. Data that is used for
controlling is retained indefinitely to ensure accountability and
support compromise recovery.
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$ COMSEC boundary
(N) "Definable perimeter encompassing all hardware, firmware, and
software components performing critical COMSEC functions, such as
key generation and key handling and storage." [C4009] (Compare:
cryptographic boundary.)
$ COMSEC custodian
(O) /U.S. Government/ "Individual designated by proper authority
to be responsible for the receipt, transfer, accounting,
safeguarding, and destruction of COMSEC material assigned to a
COMSEC account." [C4009]
$ COMSEC material
(N) /U.S. Government/ Items designed to secure or authenticate
communications or information in general; these items include (but
are not limited to) keys; equipment, devices, documents, firmware,
and software that embodies or describes cryptographic logic; and
other items that perform COMSEC functions. [C4009] (Compare:
keying material.)
$ COMSEC Material Control System (CMCS)
(O) /U.S. Government/ "Logistics and accounting system through
which COMSEC material marked 'CRYPTO' is distributed, controlled,
and safeguarded." [C4009] (See: COMSEC account, COMSEC custodian.)
$ confidentiality
See: data confidentiality.
$ concealment system
(O) "A method of achieving confidentiality in which sensitive
information is hidden by embedding it in irrelevant data." [NCS04]
(Compare: steganography.)
$ configuration control
(I) The process of regulating changes to hardware, firmware,
software, and documentation throughout the development and
operational life of a system. (See: administrative security,
harden, trusted distribution.)
Tutorial: Configuration control helps protect against unauthorized
or malicious alteration of a system and thus provides assurance of
system integrity. (See: malicious logic.)
$ confinement property
(N) /formal model/ Property of a system whereby a subject has
write access to an object only if the classification of the object
dominates the clearance of the subject. (See: *-property, Bell-
LaPadula model.)
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$ constraint
(I) /access control/ A limitation on the function of an identity,
role, or privilege. (See: rule-based access control.)
Tutorial: In effect, a constraint is a form of security policy and
may be either static or dynamic:
- "Static constraint": A constraint that must be satisfied at the
time the policy is defined, and then continues to be satisfied
until the constraint is removed.
- "Dynamic constraint": A constraint that may be defined to apply
at various times that the identity, role, or other object of
the constraint is active in the system.
$ content filter
(I) /World Wide Web/ Application software used to prevent access
to certain Web servers, such as by parents who do not want their
children to access pornography. (See: filter, guard.)
Tutorial: The filter is usually browser-based, but could be part
of an intermediate cache server. The two basic content filtering
techniques are (a) to block a specified list of URLs and (b) to
block material that contains specified words and phrases.
$ contingency plan
(I) A plan for emergency response, backup operations, and post-
disaster recovery in a system as part of a security program to
ensure availability of critical system resources and facilitate
continuity of operations in a crisis. [NCS04] (See: availability.)
$ control zone
(O) "The space, expressed in feet of radius, surrounding equipment
processing sensitive information, that is under sufficient
physical and technical control to preclude an unauthorized entry
or compromise." [NCSSG] (Compare: inspectable space, TEMPEST
zone.)
$ controlled access protection
(O) /TCSEC/ The level of evaluation criteria for a C2 computer
system.
Tutorial: The major features of the C2 level are individual
accountability, audit, access control, and object reuse.
$ controlled cryptographic item (CCI)
(O) /U.S. Government/ "Secure telecommunications or information
handling equipment, or associated cryptographic component, that is
unclassified but governed by a special set of control
requirements." [C4009] (Compare: EUCI.)
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Tutorial: This category of equipment was established in 1985 to
promote broad use of secure equipment for protecting both
classified and unclassified information in the national interest.
CCI equipment uses a classified cryptographic logic, but the
hardware or firmware embodiment of that logic is unclassified.
Drawings, software implementations, and other descriptions of that
logic remain classified. [N4001]
$ controlled interface
(I) A mechanism that facilitates the adjudication of the different
security policies of interconnected systems. (See: domain, guard.)
$ controlled security mode
(D) /U.S. DoD/ A mode of system operation wherein (a) two or more
security levels of information are allowed to be handled
concurrently within the same system when some users having access
to the system have neither a security clearance nor need-to-know
for some of the data handled by the system, but (b) separation of
the users and the classified material on the basis, respectively,
of clearance and classification level are not dependent only on
operating system control (like they are in multilevel security
mode). (See: /system operation/ under "mode", protection level.)
Deprecated Term: IDOCs SHOULD NOT use this term. It was defined in
a U.S. Government policy regarding system accreditation and was
subsumed by "partitioned security mode" in a later policy. Both
terms were dropped in still later policies.
Tutorial: Controlled mode was intended to encourage ingenuity in
meeting data confidentiality requirements in ways less restrictive
than "dedicated security mode" and "system-high security mode",
but at a level of risk lower than that generally associated with
true "multilevel security mode". This was intended to be
accomplished by implementation of explicit augmenting measures to
reduce or remove a substantial measure of system software
vulnerability together with specific limitation of the security
clearance levels of users having concurrent access to the system.
$ controlling authority
(O) /U.S. Government/ "Official responsible for directing the
operation of a cryptonet and for managing the operational use and
control of keying material assigned to the cryptonet." [C4009,
N4006]
$ cookie
1. (I) /HTTP/ Data exchanged between an HTTP server and a browser
(a client of the server) to store state information on the client
side and retrieve it later for server use.
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Tutorial: An HTTP server, when sending data to a client, may send
along a cookie, which the client retains after the HTTP connection
closes. A server can use this mechanism to maintain persistent
client-side state information for HTTP-based applications,
retrieving the state information in later connections. A cookie
may include a description of the range of URLs for which the state
is valid. Future requests made by the client in that range will
also send the current value of the cookie to the server. Cookies
can be used to generate profiles of web usage habits, and thus may
infringe on personal privacy.
2. (I) /IPsec/ Data objects exchanged by ISAKMP to prevent certain
denial-of-service attacks during the establishment of a security
association.
3. (D) /access control/ Synonym for "capability token" or
"ticket".
Deprecated Definition: IDOCs SHOULD NOT use this term with
definition 3; that would duplicate the meaning of better-
established terms and mix concepts in a potentially misleading
way.
$ Coordinated Universal Time (UTC)
(N) UTC is derived from International Atomic Time (TAI) by adding
a number of leap seconds. The International Bureau of Weights and
Measures computes TAI once each month by averaging data from many
laboratories. (See: GeneralizedTime, UTCTime.)
$ correction
(I) /security/ A system change made to eliminate or reduce the
risk of reoccurrence of a security violation or threat
consequence. (See: secondary definition under "security".)
$ correctness
(I) "The property of a system that is guaranteed as the result of
formal verification activities." [Huff] (See: correctness proof,
verification.)
$ correctness integrity
(I) The property that the information represented by data is
accurate and consistent. (Compare: data integrity, source
integrity.)
Tutorial: IDOCs SHOULD NOT use this term without providing a
definition; the term is neither well-known nor precisely defined.
Data integrity refers to the constancy of data values, and source
integrity refers to confidence in data values. However,
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correctness integrity refers to confidence in the underlying
information that data values represent, and this property is
closely related to issues of accountability and error handling.
$ correctness proof
(I) A mathematical proof of consistency between a specification
for system security and the implementation of that specification.
(See: correctness, formal specification.)
$ corruption
(I) A type of threat action that undesirably alters system
operation by adversely modifying system functions or data. (See:
disruption.)
Usage: This type of threat action includes the following subtypes:
- "Tampering": /corruption/ Deliberately altering a system's
logic, data, or control information to interrupt or prevent
correct operation of system functions. (See: misuse, main entry
for "tampering".)
- "Malicious logic": /corruption/ Any hardware, firmware, or
software (e.g., a computer virus) intentionally introduced into
a system to modify system functions or data. (See:
incapacitation, main entry for "malicious logic", masquerade,
misuse.)
- "Human error": /corruption/ Human action or inaction that
unintentionally results in the alteration of system functions
or data.
- "Hardware or software error": /corruption/ Error that results
in the alteration of system functions or data.
- "Natural disaster": /corruption/ Any "act of God" (e.g., power
surge caused by lightning) that alters system functions or
data. [FP031 Section 2]
$ counter
1. (N) /noun/ See: counter mode.
2. (I) /verb/ See: countermeasure.
$ counter-countermeasure
(I) An action, device, procedure, or technique used by an attacker
to offset a defensive countermeasure.
Tutorial: For every countermeasure devised to protect computers
and networks, some cracker probably will be able to devise a
counter-countermeasure. Thus, systems must use "defense in depth".
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$ counter mode (CTR)
(N) A block cipher mode that enhances ECB mode by ensuring that
each encrypted block is different from every other block encrypted
under the same key. [SP38A] (See: block cipher.)
Tutorial: This mode operates by first encrypting a generated
sequence of blocks, called "counters", that are separate from the
input sequence of plaintext blocks which the mode is intended to
protect. The resulting sequence of encrypted counters is
exclusive-ORed with the sequence of plaintext blocks to produce
the final ciphertext output blocks. The sequence of counters must
have the property that each counter is different from every other
counter for all of the plain text that is encrypted under the same
key.
$ Counter with Cipher Block Chaining-Message Authentication Code
(CCM)
(N) A block cipher mode [SP38C] that provides both data
confidentiality and data origin authentication, by combining the
techniques of CTR and a CBC-based message authentication code.
(See: block cipher.)
$ countermeasure
(I) An action, device, procedure, or technique that meets or
opposes (i.e., counters) a threat, a vulnerability, or an attack
by eliminating or preventing it, by minimizing the harm it can
cause, or by discovering and reporting it so that corrective
action can be taken.
Tutorial: In an Internet protocol, a countermeasure may take the
form of a protocol feature, a component function, or a usage
constraint.
$ country code
(I) An identifier that is defined for a nation by ISO. [I3166]
Tutorial: For each nation, ISO Standard 3166 defines a unique two-
character alphabetic code, a unique three-character alphabetic
code, and a three-digit code. Among many uses of these codes, the
two-character codes are used as top-level domain names.
$ Courtney's laws
(N) Principles for managing system security that were stated by
Robert H. Courtney, Jr.
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Tutorial: Bill Murray codified Courtney's laws as follows: [Murr]
- Courtney's first law: You cannot say anything interesting
(i.e., significant) about the security of a system except in
the context of a particular application and environment.
- Courtney's second law: Never spend more money eliminating a
security exposure than tolerating it will cost you. (See:
acceptable risk, risk analysis.)
-- First corollary: Perfect security has infinite cost.
-- Second corollary: There is no such thing as zero risk.
- Courtney's third law: There are no technical solutions to
management problems, but there are management solutions to
technical problems.
$ covert action
(I) An operation that is planned and executed in a way that
conceals the identity of the operator.
$ covert channel
1. (I) An unintended or unauthorized intra-system channel that
enables two cooperating entities to transfer information in a way
that violates the system's security policy but does not exceed the
entities' access authorizations. (See: covert storage channel,
covert timing channel, out-of-band, tunnel.)
2. (O) "A communications channel that allows two cooperating
processes to transfer information in a manner that violates the
system's security policy." [NCS04]
Tutorial: The cooperating entities can be either two insiders or
an insider and an outsider. Of course, an outsider has no access
authorization at all. A covert channel is a system feature that
the system architects neither designed nor intended for
information transfer.
$ covert storage channel
(I) A system feature that enables one system entity to signal
information to another entity by directly or indirectly writing a
storage location that is later directly or indirectly read by the
second entity. (See: covert channel.)
$ covert timing channel
(I) A system feature that enables one system entity to signal
information to another by modulating its own use of a system
resource in such a way as to affect system response time observed
by the second entity. (See: covert channel.)
$ CPS
(I) See: certification practice statement.
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$ cracker
(I) Someone who tries to break the security of, and gain
unauthorized access to, someone else's system, often with
malicious intent. (See: adversary, intruder, packet monkey, script
kiddy. Compare: hacker.)
Usage: Was sometimes spelled "kracker". [NCSSG]
$ CRAM
(I) See: Challenge-Response Authentication Mechanism.
$ CRC
(I) See: cyclic redundancy check.
$ credential
1. (I) /authentication/ "identifier credential": A data object
that is a portable representation of the association between an
identifier and a unit of authentication information, and that can
be presented for use in verifying an identity claimed by an entity
that attempts to access a system. Example: X.509 public-key
certificate. (See: anonymous credential.)
2. (I) /access control/ "authorization credential": A data object
that is a portable representation of the association between an
identifier and one or more access authorizations, and that can be
presented for use in verifying those authorizations for an entity
that attempts such access. Example: X.509 attribute certificate.
(See: capability token, ticket.)
3. (D) /OSIRM/ "Data that is transferred to establish the claimed
identity of an entity." [I7498-2]
Deprecated Definition: IDOCs SHOULD NOT use the term with
definition 3. As explained in the tutorial below, an
authentication process can involve the transfer of multiple data
objects, and not all of those are credentials.
4. (D) /U.S. Government/ "An object that is verified when
presented to the verifier in an authentication transaction."
[M0404]
Deprecated Definition: IDOCs SHOULD NOT use the term with
definition 4; it mixes concepts in a potentially misleading way.
For example, in an authentication process, it is the identity that
is "verified", not the credential; the credential is "validated".
(See: validate vs. verify.)
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Tutorial: In general English, "credentials" are evidence or
testimonials that (a) support a claim of identity or authorization
and (b) usually are intended to be used more than once (i.e., a
credential's life is long compared to the time needed for one
use). Some examples are a policeman's badge, an automobile
driver's license, and a national passport. An authentication or
access control process that uses a badge, license, or passport is
outwardly simple: the holder just shows the thing.
The problem with adopting this term in Internet security is that
an automated process for authentication or access control usually
requires multiple steps using multiple data objects, and it might
not be immediately obvious which of those objects should get the
name "credential".
For example, if the verification step in a user authentication
process employs public-key technology, then the process involves
at least three data items: (a) the user's private key, (b) a
signed value -- signed with that private key and passed to the
system, perhaps in response to a challenge from the system -- and
(c) the user's public-key certificate, which is validated by the
system and provides the public key needed to verify the signature.
- Private key: The private key is *not* a credential, because it
is never transferred or presented. Instead, the private key is
"authentication information", which is associated with the
user's identifier for a specified period of time and can be
used in multiple authentications during that time.
- Signed value: The signed value is *not* a credential; the
signed value is only ephemeral, not long lasting. The OSIRM
definition could be interpreted to call the signed value a
credential, but that would conflict with general English.
- Certificate: The user's certificate *is* a credential. It can
be "transferred" or "presented" to any person or process that
needs it at any time. A public-key certificate may be used as
an "identity credential", and an attribute certificate may be
used as an "authorization credential".
$ critical
1. (I) /system resource/ A condition of a system resource such
that denial of access to, or lack of availability of, that
resource would jeopardize a system user's ability to perform a
primary function or would result in other serious consequences,
such as human injury or loss of life. (See: availability,
precedence. Compare: sensitive.)
2. (N) /extension/ An indication that an application is not
permitted to ignore an extension. [X509]
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Tutorial: Each extension of an X.509 certificate or CRL is flagged
as either "critical" or "non-critical". In a certificate, if a
computer program does not recognize an extension's type (i.e.,
does not implement its semantics), then if the extension is
critical, the program is required to treat the certificate as
invalid; but if the extension is non-critical, the program is
permitted to ignore the extension.
In a CRL, if a program does not recognize a critical extension
that is associated with a specific certificate, the program is
required to assume that the listed certificate has been revoked
and is no longer valid, and then take whatever action is required
by local policy.
When a program does not recognize a critical extension that is
associated with the CRL as a whole, the program is required to
assume that all listed certificates have been revoked and are no
longer valid. However, since failing to process the extension may
mean that the list has not been completed, the program cannot
assume that other certificates are valid, and the program needs to
take whatever action is therefore required by local policy.
$ critical information infrastructure
(I) Those systems that are so vital to a nation that their
incapacity or destruction would have a debilitating effect on
national security, the economy, or public health and safety.
$ CRL
(I) See: certificate revocation list.
$ CRL distribution point
(I) See: distribution point.
$ CRL extension
(I) See: extension.
$ cross-certificate
(I) A public-key certificate issued by a CA in one PKI to a CA in
another PKI. (See: cross-certification.)
$ cross-certification
(I) The act or process by which a CA in one PKI issues a public-
key certificate to a CA in another PKI. [X509] (See: bridge CA.)
Tutorial: X.509 says that a CA (say, CA1) may issue a "cross-
certificate" in which the subject is another CA (say, CA2). X.509
calls CA2 the "subject CA" and calls CA1 an "intermediate CA", but
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this Glossary deprecates those terms. (See: intermediate CA,
subject CA).
Cross-certification of CA2 by CA1 appears similar to certification
of a subordinate CA by a superior CA, but cross-certification
involves a different concept. The "subordinate CA" concept applies
when both CAs are in the same PKI, i.e., when either (a) CA1 and
CA2 are under the same root or (b) CA1 is itself a root. The
"cross-certification" concept applies in other cases:
First, cross-certification applies when two CAs are in different
PKIs, i.e., when CA1 and CA2 are under different roots, or perhaps
are both roots themselves. Issuing the cross-certificate enables
end entities certified under CA1 in PK1 to construct the
certification paths needed to validate the certificates of end
entities certified under CA2 in PKI2. Sometimes, a pair of cross-
certificates is issued -- by CA1 to CA2, and by CA2 to CA1 -- so
that an end entity in either PKI can validate certificates issued
in the other PKI.
Second, X.509 says that two CAs in some complex, multi-CA PKI can
cross-certify one another to shorten the certification paths
constructed by end entities. Whether or not a CA may perform this
or any other form of cross-certification, and how such
certificates may be used by end entities, should be addressed by
the local certificate policy and CPS.
$ cross-domain solution
1. (D) Synonym for "guard".
Deprecated Term: IDOCs SHOULD NOT use this term as a synonym for
"guard"; this term unnecessarily (and verbosely) duplicates the
meaning of the long-established "guard".
2. (O) /U.S. Government/ A process or subsystem that provides a
capability (which could be either manual or automated) to access
two or more differing security domains in a system, or to transfer
information between such domains. (See: domain, guard.)
$ cryptanalysis
1. (I) The mathematical science that deals with analysis of a
cryptographic system to gain knowledge needed to break or
circumvent the protection that the system is designed to provide.
(See: cryptology, secondary definition under "intrusion".)
2. (O) "The analysis of a cryptographic system and/or its inputs
and outputs to derive confidential variables and/or sensitive data
including cleartext." [I7498-2]
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Tutorial: Definition 2 states the traditional goal of
cryptanalysis, i.e., convert cipher text to plain text (which
usually is clear text) without knowing the key; but that
definition applies only to encryption systems. Today, the term is
used with reference to all kinds of cryptographic algorithms and
key management, and definition 1 reflects that. In all cases,
however, a cryptanalyst tries to uncover or reproduce someone
else's sensitive data, such as clear text, a key, or an algorithm.
The basic cryptanalytic attacks on encryption systems are
ciphertext-only, known-plaintext, chosen-plaintext, and chosen-
ciphertext; and these generalize to the other kinds of
cryptography.
$ crypto, CRYPTO
1. (N) A prefix ("crypto-") that means "cryptographic".
Usage: IDOCs MAY use this prefix when it is part of a term listed
in this Glossary. Otherwise, IDOCs SHOULD NOT use this prefix;
instead, use the unabbreviated adjective, "cryptographic".
2. (D) In lower case, "crypto" is an abbreviation for the
adjective "cryptographic", or for the nouns "cryptography" or
"cryptographic component".
Deprecated Abbreviation: IDOCs SHOULD NOT use this abbreviation
because it could easily be misunderstood in some technical sense.
3. (O) /U.S. Government/ In upper case, "CRYPTO" is a marking or
designator that identifies "COMSEC keying material used to secure
or authenticate telecommunications carrying classified or
sensitive U.S. Government or U.S. Government-derived information."
[C4009] (See: security label, security marking.)
$ cryptographic
(I) An adjective that refers to cryptography.
$ cryptographic algorithm
(I) An algorithm that uses the science of cryptography, including
(a) encryption algorithms, (b) cryptographic hash algorithms, (c)
digital signature algorithms, and (d) key-agreement algorithms.
$ cryptographic application programming interface (CAPI)
(I) The source code formats and procedures through which an
application program accesses cryptographic services, which are
defined abstractly compared to their actual implementation.
Example, see: PKCS #11, [R2628].
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$ cryptographic association
(I) A security association that involves the use of cryptography
to provide security services for data exchanged by the associated
entities. (See: ISAKMP.)
$ cryptographic boundary
(I) See: secondary definition under "cryptographic module".
$ cryptographic card
(I) A cryptographic token in the form of a smart card or a PC
card.
$ cryptographic component
(I) A generic term for any system component that involves
cryptography. (See: cryptographic module.)
$ cryptographic hash
(I) See: secondary definition under "hash function".
$ cryptographic ignition key (CIK)
1. (N) A physical (usually electronic) token used to store,
transport, and protect cryptographic keys and activation data.
(Compare: dongle, fill device.)
Tutorial: A key-encrypting key could be divided (see: split key)
between a CIK and a cryptographic module, so that it would be
necessary to combine the two to regenerate the key, use it to
decrypt other keys and data contained in the module, and thus
activate the module.
2. (O) "Device or electronic key used to unlock the secure mode of
cryptographic equipment." [C4009] Usage: Abbreviated as "crypto-
ignition key".
$ cryptographic key
(I) See: key. Usage: Usually shortened to just "key".
$ Cryptographic Message Syntax (CMS)
(I) An encapsulation syntax (RFC 3852) for digital signatures,
hashes, and encryption of arbitrary messages.
Tutorial: CMS derives from PKCS #7. CMS values are specified with
ASN.1 and use BER encoding. The syntax permits multiple
encapsulation with nesting, permits arbitrary attributes to be
signed along with message content, and supports a variety of
architectures for digital certificate-based key management.
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$ cryptographic module
(I) A set of hardware, software, firmware, or some combination
thereof that implements cryptographic logic or processes,
including cryptographic algorithms, and is contained within the
module's "cryptographic boundary", which is an explicitly defined
contiguous perimeter that establishes the physical bounds of the
module. [FP140]
$ cryptographic system
1. (I) A set of cryptographic algorithms together with the key
management processes that support use of the algorithms in some
application context.
Usage: IDOCs SHOULD use definition 1 because it covers a wider
range of algorithms than definition 2.
2. (O) "A collection of transformations from plain text into
cipher text and vice versa [which would exclude digital signature,
cryptographic hash, and key-agreement algorithms], the particular
transformation(s) to be used being selected by keys. The
transformations are normally defined by a mathematical algorithm."
[X509]
$ cryptographic token
1. (I) A portable, user-controlled, physical device (e.g., smart
card or PCMCIA card) used to store cryptographic information and
possibly also perform cryptographic functions. (See: cryptographic
card, token.)
Tutorial: A smart token might implement some set of cryptographic
algorithms and might incorporate related key management functions,
such as a random number generator. A smart cryptographic token may
contain a cryptographic module or may not be explicitly designed
that way.
$ cryptography
1. (I) The mathematical science that deals with transforming data
to render its meaning unintelligible (i.e., to hide its semantic
content), prevent its undetected alteration, or prevent its
unauthorized use. If the transformation is reversible,
cryptography also deals with restoring encrypted data to
intelligible form. (See: cryptology, steganography.)
2. (O) "The discipline which embodies principles, means, and
methods for the transformation of data in order to hide its
information content, prevent its undetected modification and/or
prevent its unauthorized use.... Cryptography determines the
methods used in encipherment and decipherment." [I7498-2]
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Tutorial: Comprehensive coverage of applied cryptographic
protocols and algorithms is provided by Schneier [Schn].
Businesses and governments use cryptography to make data
incomprehensible to outsiders; to make data incomprehensible to
both outsiders and insiders, the data is sent to lawyers for a
rewrite.
$ Cryptoki
(N) A CAPI defined in PKCS #11. Pronunciation: "CRYPTO-key".
Derivation: Abbreviation of "cryptographic token interface".
$ cryptology
(I) The science of secret communication, which includes both
cryptography and cryptanalysis.
Tutorial: Sometimes the term is used more broadly to denote
activity that includes both rendering signals secure (see: signal
security) and extracting information from signals (see: signal
intelligence) [Kahn].
$ cryptonet
(I) A network (i.e., a communicating set) of system entities that
share a secret cryptographic key for a symmetric algorithm. (See:
controlling authority.)
(O) "Stations holding a common key." [C4009]
$ cryptoperiod
(I) The time span during which a particular key value is
authorized to be used in a cryptographic system. (See: key
management.)
Usage: This term is long-established in COMPUSEC usage. In the
context of certificates and public keys, "key lifetime" and
"validity period" are often used instead.
Tutorial: A cryptoperiod is usually stated in terms of calendar or
clock time, but sometimes is stated in terms of the maximum amount
of data permitted to be processed by a cryptographic algorithm
using the key. Specifying a cryptoperiod involves a tradeoff
between the cost of rekeying and the risk of successful
cryptoanalysis.
$ cryptosystem
(I) Contraction of "cryptographic system".
$ cryptovariable
(D) Synonym for "key".
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Deprecated Usage: In contemporary COMSEC usage, the term "key" has
replaced the term "cryptovariable".
$ CSIRT
(I) See: computer security incident response team.
$ CSOR
(N) See: Computer Security Objects Register.
$ CTAK
(D) See: ciphertext auto-key.
$ CTR
(N) See: counter mode.
$ cut-and-paste attack
(I) An active attack on the data integrity of cipher text,
effected by replacing sections of cipher text with other cipher
text, such that the result appears to decrypt correctly but
actually decrypts to plain text that is forged to the satisfaction
of the attacker.
$ cyclic redundancy check (CRC)
(I) A type of checksum algorithm that is not a cryptographic hash
but is used to implement data integrity service where accidental
changes to data are expected. Sometimes called "cyclic redundancy
code".
B <- 4. Definitions -> D