N <- 4. Definitions -> P
O
$ OAKLEY
(I) A key establishment protocol (proposed for IPsec but
superseded by IKE) based on the Diffie-Hellman-Merkle algorithm
and designed to be a compatible component of ISAKMP. [R2412]
Tutorial: OAKLEY establishes a shared key with an assigned
identifier and associated authenticated identities for parties;
Shirey Informational [Page 202]
RFC 4949 Internet Security Glossary, Version 2 August 2007
i.e., OAKLEY provides authentication service to ensure the
entities of each other's identity, even if the Diffie-Hellman-
Merkle exchange is threatened by active wiretapping. Also, it
provides public-key forward secrecy for the shared key and
supports key updates, incorporation of keys distributed by out-of-
band mechanisms, and user-defined abstract group structures for
use with Diffie-Hellman-Merkle.
$ object
(I) /formal model/ Trusted-system modeling usage: A system
component that contains or receives information. (See: Bell-
LaPadula model, object reuse, trusted system.)
$ object identifier (OID)
1. (N) An official, globally unique name for a thing, written as a
sequence of integers (which are formed and assigned as defined in
the ASN.1 standard) and used to reference the thing in abstract
specifications and during negotiation of security services in a
protocol.
2. (O) "A value (distinguishable from all other such values)
[that] is associated with an object." [X680]
Tutorial: Objects named by OIDs are leaves of the object
identifier tree (which is similar to but different from the X.500
Directory Information Tree). Each arc (i.e., each branch of the
tree) is labeled with a non-negative integer. An OID is the
sequence of integers on the path leading from the root of the tree
to a named object.
The OID tree has three arcs immediately below the root: {0} for
use by ITU-T, {1} for use by ISO, and {2} for use by both jointly.
Below ITU-T are four arcs, where {0 0} is for ITU-T
recommendations. Below {0 0} are 26 arcs, one for each series of
recommendations starting with the letters A to Z, and below these
are arcs for each recommendation. Thus, the OID for ITU-T
Recommendation X.509 is {0 0 24 509}. Below ISO are four arcs,
where {1 0 }is for ISO standards, and below these are arcs for
each ISO standard. Thus, the OID for ISO/IEC 9594-8 (the ISO
number for X.509) is {1 0 9594 8}.
ANSI registers organization names below the branch {joint-iso-
ccitt(2) country(16) US(840) organization(1) gov(101) csor(3)}.
The NIST CSOR records PKI objects below the branch {joint-iso-itu-
t(2) country(16) us(840) organization (1) gov(101) csor(3)}. The
U.S. DoD registers INFOSEC objects below the branch {joint-iso-
itu-t(2) country(16) us(840) organization(1) gov(101) dod(2)
infosec(1)}.
Shirey Informational [Page 203]
RFC 4949 Internet Security Glossary, Version 2 August 2007
The IETF's Public-Key Infrastructure (pkix) Working Group
registers PKI objects below the branch {iso(1) identified-
organization(3) dod(6) internet(1) security(5) mechanisms(5)
pkix(7)}. [R3280]
$ object reuse
(N) /COMPUSEC/ Reassignment and reuse of an area of a storage
medium (e.g., random-access memory, floppy disk, magnetic tape)
that once contained sensitive data objects. Before being
reassigned for use by a new subject, the area needs to be erased
or, in some cases, purged. [NCS04] (See: object.)
$ obstruction
(I) A type of threat action that interrupts delivery of system
services by hindering system operations. (See: disruption.)
Tutorial: This type of threat action includes the following
subtypes:
- "Interference": Disruption of system operations by blocking
communication of user data or control information. (See:
jamming.)
- "Overload": Hindrance of system operation by placing excess
burden on the performance capabilities of a system component.
(See: flooding.)
$ OCSP
(I) See: Online Certificate Status Protocol.
$ octet
(I) A data unit of eight bits. (Compare: byte.)
Usage: This term is used in networking (especially in OSI
standards) in preference to "byte", because some systems use
"byte" for data storage units of a size other than eight bits.
$ OFB
(N) See: output feedback.
$ off-line attack
(I) See: secondary definition under "attack".
$ ohnosecond
(D) That minuscule fraction of time in which you realize that your
private key has been compromised.
Deprecated Usage: IDOCs SHOULD NOT use this term; it is a joke for
English speakers. (See: Deprecated Usage under "Green Book".)
Shirey Informational [Page 204]
RFC 4949 Internet Security Glossary, Version 2 August 2007
$ OID
(N) See: object identifier.
$ Online Certificate Status Protocol (OCSP)
(I) An Internet protocol [R2560] used by a client to obtain from a
server the validity status and other information about a digital
certificate. (Mentioned in [X509] but not specified there.)
Tutorial: In some applications, such as those involving high-value
commercial transactions, it may be necessary either (a) to obtain
certificate revocation status that is timelier than is possible
with CRLs or (b) to obtain other kinds of status information. OCSP
may be used to determine the current revocation status of a
digital certificate, in lieu of or as a supplement to checking
against a periodic CRL. An OCSP client issues a status request to
an OCSP server and suspends acceptance of the certificate in
question until the server provides a response.
$ one-time pad
1. (N) A manual encryption system in the form of a paper pad for
one-time use.
2. (I) An encryption algorithm in which the key is a random
sequence of symbols and each symbol is used for encryption only
one time -- i.e., used to encrypt only one plaintext symbol and
thus produce only one ciphertext symbol -- and a copy of the key
is used similarly for decryption.
Tutorial: To ensure one-time use, the copy of the key used for
encryption is destroyed after use, as is the copy used for
decryption. This is the only encryption algorithm that is truly
unbreakable, even given unlimited resources for cryptanalysis
[Schn], but key management costs and synchronization problems make
it impractical except in special situations.
$ one-time password, One-Time Password (OTP)
1. (I) /not capitalized/ A "one-time password" is a simple
authentication technique in which each password is used only once
as authentication information that verifies an identity. This
technique counters the threat of a replay attack that uses
passwords captured by wiretapping.
2. (I) /capitalized/ "One-Time Password" is an Internet protocol
[R2289] that is based on S/KEY and uses a cryptographic hash
function to generate one-time passwords for use as authentication
information in system login and in other processes that need
protection against replay attacks.
Shirey Informational [Page 205]
RFC 4949 Internet Security Glossary, Version 2 August 2007
$ one-way encryption
(I) Irreversible transformation of plain text to cipher text, such
that the plain text cannot be recovered from the cipher text by
other than exhaustive procedures even if the cryptographic key is
known. (See: brute force, encryption.)
$ one-way function
(I) "A (mathematical) function, f, [that] is easy to compute, but
which for a general value y in the range, it is computationally
difficult to find a value x in the domain such that f(x) = y.
There may be a few values of y for which finding x is not
computationally difficult." [X509]
Deprecated Usage: IDOCs SHOULD NOT use this term as a synonym for
"cryptographic hash".
$ onion routing
(I) A system that can be used to provide both (a) data
confidentiality and (b) traffic-flow confidentiality for network
packets, and also provide (c) anonymity for the source of the
packets.
Tutorial: The source, instead of sending a packet directly to the
intended destination, sends it to an "onion routing proxy" that
builds an anonymous connection through several other "onion
routers" to the destination. The proxy defines a route through the
"onion routing network" by encapsulating the original payload in a
layered data packet called an "onion", in which each layer defines
the next hop in the route and each layer is also encrypted. Along
the route, each onion router that receives the onion peels off one
layer; decrypts that layer and reads from it the address of the
next onion router on the route; pads the remaining onion to some
constant size; and sends the padded onion to that next router.
$ open security environment
(O) /U.S. DoD/ A system environment that meets at least one of the
following two conditions: (a) Application developers (including
maintainers) do not have sufficient clearance or authorization to
provide an acceptable presumption that they have not introduced
malicious logic. (b) Configuration control does not provide
sufficient assurance that applications and the equipment are
protected against the introduction of malicious logic prior to and
during the operation of system applications. [NCS04] (See: "first
law" under "Courtney's laws". Compare: closed security
environment.)
Shirey Informational [Page 206]
RFC 4949 Internet Security Glossary, Version 2 August 2007
$ open storage
(N) /U.S. Government/ "Storage of classified information within an
accredited facility, but not in General Services Administration
approved secure containers, while the facility is unoccupied by
authorized personnel." [C4009]
$ Open Systems Interconnection (OSI) Reference Model (OSIRM)
(N) A joint ISO/ITU-T standard [I7498-1] for a seven-layer,
architectural communication framework for interconnection of
computers in networks. (See: OSIRM Security Architecture. Compare:
Internet Protocol Suite.)
Tutorial: OSIRM-based standards include communication protocols
that are mostly incompatible with the IPS, but also include
security models, such as X.509, that are used in the Internet.
The OSIRM layers, from highest to lowest, are (7) Application, (6)
Presentation, (5) Session, (4) Transport, (3) Network, (2) Data
Link, and (1) Physical.
Usage: This Glossary refers to OSIRM layers by number to avoid
confusing them with IPS layers, which are referred to by name.
Some unknown person described how the OSIRM layers correspond to
the seven deadly sins:
7. Wrath: Application is always angry with the mess it sees below
itself. (Hey! Who is it to be pointing fingers?)
6. Sloth: Presentation is too lazy to do anything productive by
itself.
5. Lust: Session is always craving and demanding what truly
belongs to Application's functionality.
4. Avarice: Transport wants all of the end-to-end functionality.
(Of course, it deserves it, but life isn't fair.)
3. Gluttony: (Connection-Oriented) Network is overweight and
overbearing after trying too often to eat Transport's lunch.
2. Envy: Poor Data Link is always starved for attention. (With
Asynchronous Transfer Mode, maybe now it is feeling less
neglected.)
1. Pride: Physical has managed to avoid much of the controversy,
and nearly all of the embarrassment, suffered by the others.
John G. Fletcher described how the OSIRM layers correspond to Snow
White's dwarf friends:
7. Doc: Application acts as if it is in charge, but sometimes
muddles its syntax.
Shirey Informational [Page 207]
RFC 4949 Internet Security Glossary, Version 2 August 2007
6. Sleepy: Presentation is indolent, being guilty of the sin of
Sloth.
5. Dopey: Session is confused because its charter is not very
clear.
4. Grumpy: Transport is irritated because Network has encroached
on Transport's turf.
3. Happy: Network smiles for the same reason that Transport is
irritated.
2. Sneezy: Data Link makes loud noises in the hope of attracting
attention.
1. Bashful: Physical quietly does its work, unnoticed by the
others.
$ operational integrity
(I) Synonym for "system integrity"; this synonym emphasizes the
actual performance of system functions rather than just the
ability to perform them.
$ operational security
1. (I) System capabilities, or performance of system functions,
that are needed either (a) to securely manage a system or (b) to
manage security features of a system. (Compare: operations
security (OPSEC).)
Usage: IDOCs that use this term SHOULD state a definition because
(a) the definition provided here is general and vague and (b) the
term could easily be confused with "operations security", which is
a different concept.
Tutorial: For example, in the context of an Internet service
provider, the term could refer to capabilities to manage network
devices in the event of attacks, simplify troubleshooting, keep
track of events that affect system integrity, help analyze sources
of attacks, and provide administrators with control over network
addresses and protocols to help mitigate the most common attacks
and exploits. [R3871]
2. (D) Synonym for "administrative security".
Deprecated Definition: IDOCs SHOULD NOT use this term as a synonym
for "administrative security". Any type of security may affect
system operations; therefore, the term may be misleading. Instead,
use "administrative security", "communication security", "computer
security", "emanations security", "personnel security", "physical
security", or whatever specific type is meant. (See: security
architecture. Compare: operational integrity, OPSEC.)
Shirey Informational [Page 208]
RFC 4949 Internet Security Glossary, Version 2 August 2007
$ operations security (OPSEC)
(I) A process to identify, control, and protect evidence of the
planning and execution of sensitive activities and operations, and
thereby prevent potential adversaries from gaining knowledge of
capabilities and intentions. (See: communications cover. Compare:
operational security.)
$ operator
(I) A person who has been authorized to direct selected functions
of a system. (Compare: manager, user.)
Usage: IDOCs that use this term SHOULD state a definition for it
because a system operator may or may not be treated as a "user".
$ OPSEC
1. (I) Abbreviation for "operations security".
2. (D) Abbreviation for "operational security".
Deprecated Usage: IDOCs SHOULD NOT use this abbreviation for
"operational security" (as defined in this Glossary), because its
use for "operations security" has been well established for many
years, particular in the military community.
$ ORA
See: organizational registration authority.
$ Orange Book
(D) /slang/ Synonym for "Trusted Computer System Evaluation
Criteria" [CSC1, DoD1].
Deprecated Usage: IDOCs SHOULD NOT use this term as a synonym for
"Trusted Computer System Evaluation Criteria" [CSC1, DoD1].
Instead, use the full, proper name of the document or, in
subsequent references, the abbreviation "TCSEC". (See: Deprecated
Usage under "Green Book".)
$ organizational certificate
1. (I) An X.509 public-key certificate in which the "subject"
field contains the name of an institution or set (e.g., a
business, government, school, labor union, club, ethnic group,
nationality, system, or group of individuals playing the same
role), rather than the name of an individual person or device.
(Compare: persona certificate, role certificate.)
Tutorial: Such a certificate might be issued for one of the
following purposes:
Shirey Informational [Page 209]
RFC 4949 Internet Security Glossary, Version 2 August 2007
- To enable an individual to prove membership in the
organization.
- To enable an individual to represent the organization, i.e., to
act in its name and with its powers or permissions.
2. (O) /MISSI/ A type of MISSI X.509 public-key certificate that
is issued to support organizational message handling for the U.S.
DoD's Defense Message System.
$ organizational registration authority (ORA)
1. (I) /PKI/ An RA for an organization.
2. (O) /MISSI/ An end entity that (a) assists a PCA, CA, or SCA to
register other end entities, by gathering, verifying, and entering
data and forwarding it to the signing authority and (b) may also
assist with card management functions. An ORA is a local
administrative authority, and the term refers both to the role and
to the person who plays that role. An ORA does not sign
certificates, CRLs, or CKLs. (See: no-PIN ORA, SSO-PIN ORA, user-
PIN ORA.)
$ origin authentication
(D) Synonym for "data origin authentication". (See:
authentication, data origin authentication.)
Deprecated Term: IDOCs SHOULD NOT use this term; it suggests
careless use of the internationally standardized term "data origin
authentication" and also could be confused with "peer entity
authentication."
$ origin authenticity
(D) Synonym for "data origin authentication". (See: authenticity,
data origin authentication.)
Deprecated Term: IDOCs SHOULD NOT use this term; it suggests
careless use of the internationally standardized term "data origin
authentication" and mixes concepts in a potentially misleading
way.
$ OSI, OSIRM
(N) See: Open Systems Interconnection Reference Model.
$ OSIRM Security Architecture
(N) The part of the OSIRM [I7498-2] that specifies the security
services and security mechanisms that can be applied to protect
communications between two systems. (See: security architecture.)
Shirey Informational [Page 210]
RFC 4949 Internet Security Glossary, Version 2 August 2007
Tutorial: This part of the OSIRM includes an allocation of
security services to protocol layers. The following table shows
which security services (see definitions in this Glossary) are
permitted by the OSIRM in each of its layers. (Also, an
application process that operates above the Application Layer may
itself provide security services.) Similarly, the table suggests
which services are suitable for each IPS layer. However,
explaining and justifying these allocations is beyond the scope of
this Glossary.
Legend for Table Entries:
O = Yes, [I7498-2] permits the service in this OSIRM layer.
I = Yes, the service can be incorporated in this IPS layer.
* = This layer subsumed by Application Layer in IPS.
IPS Protocol Layers +-----------------------------------------+
|Network| Net |In-| Trans | Application |
| H/W |Inter|ter| -port | |
| |-face|net| | |
OSIRM Protocol Layers +-----------------------------------------+
| 1 | 2 | 3 | 4 | 5 | 6 | 7 |
Confidentiality +-----------------------------------------+
- Datagram | O I | O I | O I | O I | | O * | O I |
- Selective Field | | | I | | | O * | O I |
- Traffic Flow | O | | O | | | | O |
-- Full | I | | | | | | |
-- Partial | | I | I | | | | I |
Integrity +-----------------------------------------+
- Datagram | I | I | O I | O I | | | O I |
- Selective Field | | | I | | | | O I |
- Stream | | | O I | O I | | | O I |
Authentication +-----------------------------------------+
- Peer Entity | | I | O I | O I | | | O I |
- Data Origin | | I | O I | O I | | | O I |
Access Control +-----------------------------------------+
- type as appropriate | | I | O I | O I | | | O I |
Non-Repudiation +-----------------------------------------+
- of Origin | | | | | | | O I |
- of Receipt | | | | | | | O I |
+-----------------------------------------+
$ OTAR
(N) See: over-the-air rekeying.
$ OTP
(I) See: One-Time Password.
Shirey Informational [Page 211]
RFC 4949 Internet Security Glossary, Version 2 August 2007
$ out-of-band
(I) /adjective, adverb/ Information transfer using a channel or
method that is outside (i.e., separate from or different from) the
main channel or normal method.
Tutorial: Out-of-band mechanisms are often used to distribute
shared secrets (e.g., a symmetric key) or other sensitive
information items (e.g., a root key) that are needed to initialize
or otherwise enable the operation of cryptography or other
security mechanisms. Example: Using postal mail to distribute
printed or magnetic media containing symmetric cryptographic keys
for use in Internet encryption devices. (See: key distribution.)
$ output feedback (OFB)
(N) A block cipher mode that modifies ECB mode to operate on
plaintext segments of variable length less than or equal to the
block length. [FP081] (See: block cipher, [SP38A].)
Tutorial: This mode operates by directly using the algorithm's
previously generated output block as the algorithm's next input
block (i.e., by "feeding back" the output block) and combining
(exclusive OR-ing) the output block with the next plaintext
segment (of block length or less) to form the next ciphertext
segment.
$ outside attack
(I) See: secondary definition under "attack". Compare: outsider.)
$ outsider
(I) A user (usually a person) that accesses a system from a
position that is outside the system's security perimeter.
(Compare: authorized user, insider, unauthorized user.)
Tutorial: The actions performed by an outsider in accessing the
system may be either authorized or unauthorized; i.e., an outsider
may act either as an authorized user or as an unauthorized user.
$ over-the-air rekeying (OTAR)
(N) Changing a key in a remote cryptographic device by sending a
new key directly to the device via a channel that the device is
protecting. [C4009]
$ overload
(I) /threat action/ See: secondary definition under "obstruction".
N <- 4. Definitions -> P