access control
A set of procedures performed by hardware, software and administrators
to monitor access, identify users requesting access, record access attempts,
and grant or deny access. Compare with authorization.
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Advanced Encryption Standard (AES)
A NIST-standard secret key cryptography method that uses 128, 192
and 256-bit keys. Officially replacing the Triple DES method in 2001,
AES uses the Rijndael algorithm. AES can be encrypted in one pass instead
of three, and its key size is greater than Triple DES's 168 bits. Compare
with Triple DES.
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AES
See Advanced Encryption Standard (AES).
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ARCFOUR
A public domain cipher that interoperates with RSA Security Inc.’s
RC4® stream cipher.
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ASN.1
ASN.1 (Abstract Syntax Notation One) is a standard way to describe
a message (a unit of application data) that can be sent or received
in a network. ASN.1 is divided into two parts: (1) the rules of syntax
for describing the contents of a message in terms of data type and content
sequence or structure and (2) how you actually encode each data item
in a message. ASN.1 is defined in two ISO standards for applications
intended for the Open Systems Interconnection (OSI) framework:
- ISO 8824/ITU X.208 specifies the syntax (for example, which data
item comes first in the message and what its data type is)
- ISO 8825/ITU X.209 specifies the basic encoding rules for ASN.1
(for example, how to state how long a data item is)
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asymmetric cryptography
See public key cryptography.
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attack
An attempt to subvert or bypass a system's security, which may or may
not be successful. Attacks may be active or passive. An active attack
attempts to alter or destroy data. A passive attack attempts to intercept
and read data without altering it.
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authentication
Authentication is the process of determining whether someone or something
is, in fact, who or what it is declared to be. In private and public
computer networks (including the Internet), authentication is commonly
done through the use of logon passwords. Knowledge of the password is
assumed to guarantee that the user is authentic. Each user registers
initially (or is registered by someone else), using an assigned or self-declared
password. On each subsequent use, the user must know and use the previously
declared password. The weakness in this system for transactions that
are significant (such as the exchange of money) is that passwords can
often be stolen, accidentally revealed, or forgotten.
For this reason, Internet business and many other transactions require
a more stringent authentication process. The use of digital
certificates issued and verified by a Certificate
Authority (CA) as part of a Public Key Infrastructure
(PKI) is considered likely to become the standard way to perform
authentication on the Internet.
Logically, authentication precedes authorization
(although they may often seem to be combined).
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Authentication Service (AS)
The portion of a Kerberos Key
Distribution Center (KDC) that issues tickets
and secret session keys based on a user password or encryption key.
The AS can issue Ticket-Granting Tickets (TGTs) and
other service tickets.
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authorization
Authorization is the process of giving someone permission to do or
have something. In multi-user computer systems, a system administrator
defines for the system which users are allowed access to the system
and what privileges of use (such as access to which file directories,
hours of access, amount of allocated storage space, and so forth). Assuming
that someone has logged in to a computer operating system or application,
the system or application may want to identify what resources the user
can be given during this session. Thus, authorization is sometimes seen
as both the preliminary setting up of permissions by a system adminstrator
and the actual checking of the permission values that have been set
up when a user is getting access.
Logically, authorization is preceded by authentication.
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block cipher
A block cipher is a method of encrypting text (to produce ciphertext)
in which a cryptographic key and algorithm are used
to encrypt/decrypt a block of data (for example, 64 contiguous bits)
at once as a group rather than to one bit at a time. An alternative
method is a stream cipher.
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Blowfish
Blowfish is a block cipher that uses a
variable-length key, from 32 bits to 448 bits. Blowfish was designed
in 1993 by Bruce Schneier as an alternative to existing encryption algorithms.
Designed with 32-bit instruction processors in mind, it is significantly
faster than DES. Since its origin, it has been analyzed considerably.
Blowfish is unpatented, license-free and available free for all uses.
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brute force cracking
Brute force (also known as brute force cracking) is a trial and error
method used by application programs to decode encrypted data such as
passwords or DES keys, through exhaustive effort
(using brute force) rather than employing intellectual strategies. Just
as a burglar might break into, or "crack" a safe by trying
many possible combinations, a brute force cracking application proceeds
through all possible combinations of legal characters in sequence. Brute
force is considered to be an infallible, although usually infeasible,
attack.
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CBC
See Cipher Block Chaining (CBC) mode.
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certificate
See digital certificate.
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Certificate Revocation List (CRL)
Certificate Revocation List (CRL) is one of two common methods when
using a Public Key Infrastructure (PKI) for maintaining
access to servers in a network. The other, newer method, which has superseded
CRL in some cases, is Online Certificate Status Protocol
(OCSP).
The CRL is exactly what its name implies—a list of subscribers
paired with digital certificate status. The list
enumerates revoked certificates along with the reasons for revocation.
The dates of certificate issue, and the entities that issued them, are
also included. In addition, each list contains a proposed date for the
next release. When a potential user attempts to access a server, the
server allows or denies access based on the CRL entry for that particular
user.
The main limitation of CRL is the fact that updates must be frequently
downloaded to keep the list current. OCSP overcomes this limitation
by checking certificate status in real-time.
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Certificate Authority (CA)
A Certificate Authority (CA) is an authority in a network that issues
and manages security credentials and public keys for message encryption.
As part of a Public Key Infrastructure (PKI), a CA
checks with a Registration Authority (RA) to verify
information provided by the requestor of a digital certificate.
If the RA verifies the requestor's information, the CA can then issue
a certificate.
Depending on the PKI implementation, the certificate includes the
owner's public key, the expiration date of the certificate, the owner's
name and other information about the public key owner.
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CFB
See Cipher-Feedback (CFB) mode.
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checksum
A one-way function applied to data to provide a method of verifying
its integrity. See message digest.
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cipher
A cipher is any method of encrypting text (concealing its readability
and meaning). It is also sometimes used to refer to the encrypted text
message itself although here the term ciphertext
is preferred. Its origin is the Arabic sifr, meaning empty
or zero.
Some ciphers work by simply realigning the alphabet or otherwise manipulating
the text in some consistent pattern. However, almost all serious ciphers
use both a key (a variable that is combined in some
way with the unencrypted text) and an algorithm (a formula for combining
the key with the text). See block cipher,
stream cipher.
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Cipher Block Chaining (CBC) mode
A cipher mode where the first block of the
ciphertext is produced by encrypting the first
block of plaintext, then XORing
the result with an IV of the same length. Subsequent
blocks of ciphertext are produced by encrypting the corresponding block
of plaintext, then XORing the result with the preceding block of ciphertext.
This is the most common block cipher mode.
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Cipher-Feedback (CFB) mode
A cipher mode used to transmit data in smaller
chunks than the block size. A state vector, whose size is the block
size of the underlying block cipher, is used. During encryption, the
state vector is filled with the initialization vector
(IV). Then, for example, when you want to transmit N bits in your
N-bit CFB, you encrypt the whole queue, take the leftmost N bits and
XOR them with the N bits you want to transmit to arrive
at the ciphertext. Then you shift your state
vector N bits to the left, discarding the N leftmost bits and place
the N bits you just transmitted into the N rightmost bits of the state
vector.
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cipher mode
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ciphertext
Ciphertext is encrypted text. Compare with plaintext.
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CMS
See Cryptographic Message Syntax (CMS).
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confidentiality
The assurance that information is not disclosed to inappropriate entities
or processes.
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counter mode
A cipher mode used to define a pseudo random
keystream generator using a block cipher.
The keystream can be used for additive encryption, key derivation or
any other application requiring pseudo random data.
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CRL
See Certificate Revocation List (CRL).
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Cryptographic Message Syntax (CMS)
The Cryptographic Message Syntax (CMS) describes an encapsulation
syntax for data protection. It supports digital signatures,
Message Authentication Codes (MAC) and encryption.
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CTR mode
See counter mode.
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cryptography
Cryptography is the science of information security. The word is derived
from the Greek kryptos, meaning hidden. Cryptography is closely
related to the disciplines of cryptology and cryptanalysis. Cryptography
includes techniques such as microdots, merging words with images, and
other ways to hide information in storage or transit. However, in today's
computer-centric world, cryptography is most often associated with scrambling
plaintext into ciphertext
(a process called encryption), then back again
(known as decryption). Individuals who practice
this field are known as cryptographers.
Modern cryptography concerns itself with the following four objectives:
- Confidentiality (the information
cannot be understood by anyone for whom it was unintended)
- Integrity (the information cannot be altered
in storage or transit between sender and intended receiver without
the alteration being detected)
- Non-repudiation (the creator/sender of
the information cannot deny at a later stage his or her intentions
in the creation or transmission of the information)
- Authentication (the sender and receiver
can confirm each other’s identity and the origin/destination
of the information)
Procedures and protocols that meet some or all of the above criteria
are known as cryptosystems. Cryptosystems are often thought to refer
only to mathematical procedures and computer programs; however, they
also include the regulation of human behavior, such as choosing hard-to-guess
passwords, logging off unused systems, and not discussing sensitive
procedures with outsiders.
Because governments do not wish certain entities in and out of their
countries to have access to ways to receive and send hidden information
that may be a threat to national interests, cryptography has been subject
to various restrictions in many countries, ranging from limitations
of the usage and export of software to the public dissemination of mathematical
concepts that could be used to develop cryptosystems. However, the Internet
has allowed the spread of powerful programs and, more importantly, the
underlying techniques of cryptography, so that today many of the most
advanced cryptosystems and ideas are now in the public domain.
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Data Encryption Standard (DES)
A NIST-standard secret key cryptography method
that uses a 56-bit key. DES is based on an IBM algorithm that was further
developed by the US National Security Agency. It uses the block
cipher method which breaks the text into 64-bit blocks before encrypting
them. DES encryption is very fast and widely used. The secret key may
be kept a total secret and used over again. Alternatively, a key can
be randomly generated for each session, in which case the new key is
transmitted to the recipient using a public
key cryptography method such as RSA. See also
Triple DES.
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decryption
Decryption is the process of converting encrypted data, called a ciphertext,
back into its original form, so it can be understood. Contrast with
encryption.
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Denial of Service (DoS)
An attack that is specifically designed to prevent
the normal functioning of a system, and thereby to prevent lawful access
to that system and its data by its authorized users. DoS can be caused
by the destruction or modification of data, by bringing down the system,
or by overloading the system's servers to the extent that service to
authorized users is delayed or prevented.
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DES
See Data Encryption Standard (DES).
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DESede
See Triple DES.
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Diffie–Hellman key exchange algorithm
A cryptographic technique that enables sending and receiving parties
to derive a shared, secret key at both ends without disclosing it to
a potential attacker. Using a common modulus and base, both sides use
a different random number as a power to perform a modular exponentiation.
The results are sent to each other. The receiving party raises the received
number to the same random power they used before and the results are
the same on both sides.
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digest algorithm
A one-way function used to map a large block of data to a fixed-size
message. Digest algorithms are not enough to ensure message integrity
by themselves however, as an attacker can simply change both the message
and the digest. For this reason digest algorithms are usually combined
with a cipher to protect the digest itself from
being tampered with.
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digital certificate
A digital certificate is an electronic 'license' that establishes
your credentials when doing business or other transactions on the Web.
It is issued by a Certificate Authority (CA). It contains
your name, a serial number, expiration dates, a copy of the certificate
holder's public key (used for encrypting messages and digital
signatures), and the digital signature of the certificate-issuing
authority so that a recipient can verify that the certificate is real.
Most digital certificates conform to a standard, X.509.
Digital certificates can be kept in registries so that authenticating
users can look up other users' public keys.
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digital signature
A digital signature (not to be confused with a digital
certificate) is an electronic signature that can be used to authenticate
the identity of the sender of a message or the signer of a document,
and possibly to ensure that the original content of the message or document
that has been sent is unchanged. Digital signatures are easily transportable,
cannot be imitated by someone else (without access to the private
key), and can be automatically time-stamped. The ability to ensure
that the original signed message arrived means that the sender cannot
easily repudiate it later.
A digital signature can be used with any kind of message, whether
it is encrypted or not, simply so that the receiver can be sure of the
sender's identity and that the message arrived intact. A digital certificate
contains the digital signature of the certificate-issuing authority
so that anyone can verify that the certificate is real.
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Digital Signature Algorithm (DSA)
The algorithm used in the Digital Signature Standard
(DSS) by the US government. DSA is a pair of large numbers that
are computed according to the specified algorithm within parameters
that enable the authentication of the signatory, and as a consequence,
the integrity of the data attached. Digital signatures are generated
through DSA, as well as verified. Signatures are generated in conjunction
with the use of a private key; verification
takes place in reference to a corresponding public
key. Each signatory has their own paired public (assumed to be known
to the general public) and private (known only to the user) keys. Because
a signature can only be generated by an authorized person using their
private key, the corresponding public key can be used by anyone to verify
the signature.
A data summary of the information (called a message
digest) is created through the use of a hash function
(called the Secure Hash Standard, or SHS, and specified in FIPS-180).
The data summary is used in conjuntion with the DSA algorithm to create
the digital signature that is sent with the message. Signature verification
involves the use of the same hash function.
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Digital Signature Standard (DSS)
Digital Signature Standard (DSS) is the Digital Signature
Algorithm (DSA) developed by the US National Security Agency (NSA)
to generate a digital signature for the authentication
of electronic documents. DSS was put forth by the National
Institute of Standards and Technology (NIST) in 1994, and has become
the US Government standard for authentication
of electronic documents.
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DSA
See Digital Signature Algorithm (DSA).
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DSS
See Digital Signature Standard (DSS).
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ECB
See Electronic Codebook (ECB) mode.
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Electronic Codebook (ECB) mode
A cipher mode where each block of the plaintext
is operated on by the cipher, resulting in a corresponding block of
ciphertext. This is the simplest of the cipher
modes.
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encryption
Encryption is the conversion of data into a form, called a ciphertext,
that cannot be easily understood by unauthorized people. Contrast with
decryption.
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envelope
The use of two layers of security to protect data. First the data
is encoded using symmetric encryption, then the key to decrypt the data
is encrypted using public key encryption.
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firewall
A system or combination of systems that enforces a boundary between
two or more networks.
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Generic Security Service (GSS)
API
A C API for distributed security services. Described in IETF RFC 2743.
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GSS-API
See Generic Security Service (GSS) API.
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Hardware Security Module (HSM)
A hardware-based security device that generates, stores and protects
cryptographic keys.
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Hashed Message Authentication Code (HMAC)
A mechanism for message authentication using cryptographic hash
functions. HMAC can be used with any iterative cryptographic hash
function, for example, MD5 and SHA-1,
in combination with a secret shared key. The cryptographic
strength of HMAC depends on the properties of the underlying hash function.
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hash function
Hashing is the transformation of a string of characters into a usually
shorter fixed-length value or key that represents the original string.
Hashing is also used to encrypt and decrypt digital signatures
(used to authenticate message senders
and receivers). The digital signature is transformed with the hash function
and then both the hashed value (known as a message
digest) and the signature are sent in separate transmissions to
the receiver. Using the same hash function as the sender, the receiver
derives a message digest from the signature and compares it with the
message digest it also received. They should be the same.
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HMAC
See Hashed Message Authentication Code (HMAC).
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HSM
See Hardware Security Module (HSM).
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HTTPS
HTTPS (Secure Hypertext Transfer Protocol) is HTTP over Secure
Sockets Layer (SSL), which are HTTP packets sent as encrypted data.
This is the mechanism by which data is securely transmitted over the
Internet between a browser client and a server.
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IDEA
IDEA (International Data Encryption Algorithm) is an encryption
algorithm developed at ETH in Zurich, Switzerland. It uses a block
cipher with a 128-bit key, and is generally considered to be very
secure. IDEA is patented in the United States and in most European countries.
The patent is held by Ascom-Tech. Non-commercial use of IDEA is free.
Commercial licenses can be obtained by contacting Ascom-Tech.
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IETF
See Internet Engineering Task Force (IETF).
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initialization vector (IV)
An intialization vector (IV) is a sequence of random bytes appended
to the front of the plaintext before encryption
by a block cipher. Adding the IV to the beginning
of the plaintext eliminates the possibility
of having the initial ciphertext block the
same for any two messages encrypted with the same algorithm and symmetric
key. See cipher mode, Cipher
Block Chaining (CBC) mode.
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integrity
The prevention of unauthorized modification of information.
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Internet Engineering Task Force (IETF)
A public forum that develops standards and resolves operational issues
for the Internet.
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IV
See initialization vector (IV).
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KDC
See Key Distribution Center (KDC).
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Kerberos
Kerberos is a secure method for authenticating a request for a service
in a computer network. Kerberos was developed in the Athena Project
at the Massachusetts Institute of Technology (MIT). The name is taken
from Greek mythology; Kerberos was a three-headed dog who guarded the
gates of Hades. Kerberos lets a user request an encrypted "ticket"
from an authentication process that can
then be used to request a particular service from a server. The user's
password does not have to pass through the network.
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Kerberized application
A software application that requires or performs Kerberos
authentication.
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key
A key is a variable value that is applied using an algorithm to a
string or block of unencrypted text to produce encrypted text, or to
decrypt encrypted text. The length of the key is a factor in considering
how difficult it will be to decrypt the text in a given message.
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Key Distribution Center (KDC)
The service which implements Kerberos authentication
via the Authentication Service (AS) and Ticket-Granting
Service (TGS). The KDC has a copy of every encryption key
associated with every principal. Most KDC implementations store the
principals in a database, so the KDC may be referred to as the Kerberos
database.
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key management
The process of securely generating and distributing cryptographic keys
to authorized recipients. Among other functions, key management allows
user-unique public keys to be certified for
use by individuals or organizations.
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key pair
In public key cryptography, a public
key and its corresponding private key.
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KeyStore
An interface that allows the management of certificates,
public keys and private
keys for use in a Public Key Infrastructure (PKI).
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LDAP
See Lightweight Directory Access Protocol (LDAP).
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Lightweight Directory Access Protocol (LDAP)
LDAP (Lightweight Directory Access Protocol) is a software protocol
for enabling anyone to locate organizations, individuals, and other
resources such as files and devices in a network, whether on the public
Internet or on a corporate intranet. LDAP is a "lightweight"
version of Directory Access Protocol (DAP), which is part of X.500,
a standard for directory services in a network. Netscape includes it
in its latest Communicator suite of products. Microsoft includes it
as part of what it calls Active Directory in a number of products including
Outlook Express. Novell's NetWare Directory Services interoperates with
LDAP. Cisco also supports it in its networking products.
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MAC
See Message Authentication Code (MAC).
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MD2
MD2 (Message Digest 2) is an earlier, 8-bit version of MD5,
an algorithm used to verify data integrity through the creation of a
128-bit message digest from data input (which may be a message of any
length) that is claimed to be as unique to that specific data as a fingerprint
is to a specific individual. MD2, which was developed by Professor Ronald
L. Rivest of MIT, is intended for use with digital signature
applications, which require that large files must be compressed by a
secure method before being encrypted with a secret key, under a public
key cryptosystem. MD2, MD4 (a later version),
and MD5, the latest version, have similar structures, but MD2 was optimized
for 8-bit machines, in comparison with the two later formulas, which
are optimized for 32-bit machines.
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MD4
MD4 (Message Digest 4), an earlier version of MD5,
is an algorithm that is used to verify data integrity through the creation
of a 128-bit message digest from data input
(which may be a message of any length) that is claimed to be as unique
to that specific data as a fingerprint is to the specific individual.
MD4, which was developed by Professor Ronald L. Rivest of MIT, is intended
for use with digital signature applications, which
require that large files must be compressed by a secure method before
being encrypted with a secret key, under a public
key cryptosystem.
It has been demonstrated that collisions for the full version of MD4
can be found in under a minute on a typical PC, therefore, MD4 should
be considered broken.
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MD5
MD5 (Message Digest 5) is an algorithm that is used to verify data
integrity through the creation of a 128-bit message
digest from data input (which may be a message of any length) that
is claimed to be as unique to that specific data as a fingerprint is
to the specific individual. MD5, which was developed by Professor Ronald
L. Rivest of MIT, is intended for use with digital signature
applications, which require that large files must be compressed by a
secure method before being encrypted with a secret key, under a public
key cryptosystem.
According to IETF RFC 1321, it is "computationally infeasible"
that any two messages that have been input to the MD5 algorithm could
have as the output the same message digest, or that a false message
could be created through apprehension of the message
digest. MD5 is the third message digest algorithm created by Rivest.
All three (the others are MD2 and MD4)
have similar structures, but MD2 was optimized for 8-bit machines, in
comparison with the two later formulas, which are optimized for 32-bit
machines. The MD5 algorithm is an extension of MD4, which the critical
review found to be fast, but possibly not absolutely secure. In comparison,
MD5 is not quite as fast as the MD4 algorithm, but offers much more
assurance of data security.
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Message Authentication Code (MAC)
A number computed from the contents of a text message that is used
to authenticate the message. The MAC is
a checksum that is computed using an algorithm
and secret key and then sent with the message. The recipient recomputes
the MAC at the other end using the same algorithm and secret key and
compares it to the one that is sent. If they are the same, the message
has not been tampered with. A MAC is like a digital signature,
except that a secret key was used in its creation rather than a private
key.
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message digest
The representation of text in the form of a single string of digits,
created using a one-way hash function. Encrypting
a message digest with a private key creates
a digital signature.
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MIME
An electronic mail protocol that allows users to attach binary files
to e-mail messages. Most mail packages support the MIME protocol. It
is defined for e-mail use in RFC 1521 and 1522, and has been extended
by other RFCs for use in applications.
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National Institute of Standards
and Technology (NIST)
NIST is the National Institute of Standards and Technology, a unit
of the US Commerce Department. Formerly known as the National Bureau
of Standards, NIST promotes and maintains measurement standards. It
also has active programs for encouraging and assisting industry and
science to develop and use these standards.
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NIST
See National Institute of Standards and Technology
(NIST).
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non-repudiation
The process by which the sender of data is provided with proof of delivery,
and the receiver is assured of the sender's identity. This is non-repudiation,
so that neither party can deny either sending or receiving the data
in question.
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OCSP
See Online Certificate Status Protocol (OCSP).
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OFB
See Output-Feedback (OFB) mode.
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Online Certificate Status Protocol (OCSP)
The Online Certificate Status Protocol (OCSP) is one of two common
schemes for maintaining the security of a server and other network resources.
The other, older method, which OCSP has superseded in some scenarios,
is known as Certificate Revocation List (CRL).
OCSP overcomes the chief limitation of CRL – the fact that updates
must be frequently dowloaded to keep the list current at the client
end. When a user attempts to access a server, OCSP sends a request for
certificate status information. The server sends
back a response of "current", "expired" or "unknown".
The protocol specifies the syntax for communication between the server
(which contains the certificate status) and the client application (which
is informed of that status). OCSP allows users with expired certificates
a grace period, so they can access servers for a limited time before
renewing.
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Output-Feedback (OFB) mode
A cipher mode similar to Cipher-Feedback
(CFB) mode, with the exception that instead of replacing the rightmost,
“N” bits, with the XOR of the encryption
output and the plaintext, you replace them
with the actual encryption output. If N = 8, this turns the block
cipher into a stream cipher, with the result
that the key stream has no relationship with the plaintext. Eventually,
however, the state vector will repeat a value, after which all subsequent
values start to repeat. This presents a security problem if the mode
develops any short cycles.
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padding algorithm
An algorithm that is used to fill up the unused portions of encryption
blocks. The padding is in the form of some regular pattern, for example,
zeros, ones, or alternating zeros and ones.
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plaintext
Plaintext is ordinary readable text before being encrypted
into ciphertext or after being decrypted.
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PKCS
See Public Key Cryptography Standards (PKCS).
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PKI
See Public Key Infrastructure (PKI).
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private key
A private (or secret key) is an encryption/decryption
key known only to the party or parties that exchange secret messages.
In traditional secret key cryptography, a key would be shared by the
communicators so that each could encrypt and decrypt messages. The risk
in this system is that if either party loses the key or it is stolen,
the system is broken. A more recent alternative is to use a combination
of public and private keys. In this system, a public
key is used together with a private key.
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PRNG
See pseudo random number generator (PRNG).
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pseudo random number generator (PRNG)
A pseudo-random number generator (PRNG) is a program written for,
and used in, probability and statistics applications when large quantities
of random digits are needed. Many algorithms have been developed in
an attempt to produce truly random sequences of numbers, endless strings
of digits in which it is theoretically impossible to predict the next
digit in the sequence based on the digits up to a given point. But the
very existence of the algorithm, no matter how sophisticated, means
that the next digit can be predicted. This has given rise to the term
pseudo-random for such machine-generated strings of digits. They are
equivalent to random-number sequences for most applications, but they
are not truly random according to the rigorous definition.
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public key
A public key is a value provided by some designated authority as an
encryption key that, combined with a private
key derived from the public key, can be used to effectively encrypt
messages and digital signatures.
The use of combined public and private keys is known as public
key or asymmetric cryptography. A system for using public keys is
called a Public Key Infrastructure (PKI).
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public key cryptography
An encryption system developed by Whitfield Diffie and Martin Hellman
that uses two keys; one public and one private.
Anyone can know a person's public key; no-one should ever know a person's
private key. Encrypted messages may be sent to a recipient by using
that person's public key. However, the message can only be decrypted
by the associated private key. In this way, decryption keys need never
be published nor transmitted.
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Public Key Cryptography Standards (PKCS)
The Public Key Cryptography Standards (PKCS) are a set of inter-vendor
standard protocols for making possible secure information exchange on
the Internet using a Public Key Infrastructure (PKI).
The standards include RSA encryption, password-based
encryption, extended certificate syntax, and cryptographic
message syntax (CMS) for S/MIME, RSA Security,
Inc.'s proposed standard for secure e-mail. The standards were developed
by RSA Laboratories in cooperation with a consortium that included Apple,
Microsoft, DEC, Lotus, Sun, and MIT.
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Public Key Infrastructure (PKI)
A Public Key Infrastructure (PKI) enables users of a basically unsecure
public network such as the Internet to securely and privately exchange
data and money through the use of a public and a private cryptographic
key pair that is obtained and shared through
a trusted authority. The PKI provides for a digital
certificate that can identify an individual or an organization and
directory services that can store and, when necessary, revoke the certificates.
The PKI assumes the use of public key cryptography,
which is the most common method on the Internet for authenticating a
message sender or encrypting a message. Traditional cryptography has
usually involved the creation and sharing of a secret key for the encryption
and decryption of messages. This secret or
private key system has the significant flaw
that if the key is discovered or intercepted by someone else, messages
can easily be decrypted. For this reason, public key cryptography and
the PKI is the preferred approach on the Internet. (The private key
system is sometimes known as symmetric cryptography and the
public key system as asymmetric cryptography.)
A public key infrastructure consists of:
- A Certificate Authority (CA) that issues and verifies
digital certificate. A certificate includes the public
key or information about the public key.
- A Registration Authority (RA) that acts as the
verifier for the CA before a digital certificate is issued to a requestor.
- One or more directories where the certificates (with their public
keys) are held
- A certificate management system
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RA
See Registration Authority (RA).
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RC2
(Ron’s Code 2 or Rivest Cipher 2) A variable-key-size 64-bit
block cipher.
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RC4®
(Ron’s Code 4 or Rivest Cipher 4) A widely used stream cipher.
See ARCFOUR.
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reduced sign-on
See Single Sign-On (SSO).
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Registration Authority (RA)
A Registration Authority (RA) is an authority in a network that verifies
user requests for a digital certificate and tells
the Certificate Authority (CA)to issue it. RAs are
part of a Public Key Infrastructure (PKI), a networked
system that enables companies and users to exchange information and
money safely and securely. The digital certificate contains a public
key that is used to encrypt and decrypt messages and a digital
signature.
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Rijndael algorithm
Rijndael (pronounced rain-dahl) is the algorithm that has been selected
by the US National Institute of Standards and Technology
(NIST) as the candidate for the Advanced Encryption
Standard (AES). Rijndael will begin to supplant the Data
Encryption Standard (DES)—and later Triple
DES—over the next few years in many cryptography applications.
The algorithm was designed by two Belgian cryptologists, Vincent Rijmen
and Joan Daemen, whose surnames are reflected in the cipher's name.
The Rijndael algorithm is a new generation symmetric block
cipher that supports key sizes of 128, 192 and 256 bits, with data
handled in 128-bit blocks—however, in excess of AES design criteria,
the block sizes can mirror those of the keys.
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RSA
RSA is an Internet encryption and authentication
system that uses an algorithm developed in 1977 by Ron Rivest, Adi Shamir
and Leonard Adleman. The RSA algorithm is the most commonly used encryption
and authentication algorithm and is included as part of the Web browsers
from Microsoft and Netscape. It is also part of Lotus Notes, Intuit's
Quicken and many other products. The encryption system is owned by RSA
Security, Inc.
The algorithm involves multiplying two large prime numbers and through
additional operations deriving a set of two numbers that constitutes
the public key and another set that is the
private key. Once the keys have been developed,
the original prime numbers are no longer important and can be discarded.
Both the public and the private keys are needed for encryption/decryption
but only the owner of a private key ever needs to know it. Using the
RSA system, the private key never needs to be sent across the Internet.
The private key is used to decrypt text that has been encrypted with
the public key.
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salt
Salt is a random string of data used to modify a password hash. Salt
can be added to the hash to prevent a collision by uniquely identifying
a user's password, even if another user in the system has selected the
same password. Salt can also be added to make it more difficult for
an attacker to break into a system by using password hash-matching strategies
because adding salt to a password hash prevents an attacker from testing
known dictionary words across the entire system.
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secret key
See private key.
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Secure Sockets Layer (SSL)
The Secure Sockets Layer (SSL) is a commonly-used protocol for managing
the security of message transmission on the Internet. SSL uses a program
layer located between the Internet's Hypertext Transfer Protocol (HTTP)
and Transport Control Protocol (TCP) layers. SSL is included as part
of both the Microsoft and Netscape browsers and most Web server products.
Developed by Netscape, SSL also gained the support of Microsoft and
other Internet client/server developers, becoming the de facto standard
until evolving into Transport Layer Security (TLS).
The sockets part of the term refers to the sockets
method of passing data back and forth between a client and a server
program in a network or between program layers in the same computer.
SSL uses the public/private key encryption system from RSA, which also
includes the use of a digital certificate.
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SHA-1
SHA-1 (Secure Hash Algorithm-1) is a popular one-way hash algorithm
used to create digital signatures. SHA-1 is similar
to the MD4 and MD5 algorithms,
but it is slightly slower and more secure.
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signature
See digital signature.
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silent sign-on
See Single Sign-On (SSO).
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Simple and Protected GSS-API Negotiation Mechanism
(SPNEGO)
A GSS-API mechanism that allows the secure negotiation of the mechanism
to be used by two different GSS-API implementations. In essence, SPNEGO
defines a universal but separate mechanism, solely for the purpose of
negotiating the use of other security mechanisms. SPNEGO itself does
not define or provide authentication or data protection, although it
can allow negotiators to determine if the negotiation has been subverted,
once a mechanism is established.
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Simple Certificate Enrollment Protocol (SCEP)
A certificate management protocol developed by Cisco Systems that
Public Key Infrastructure (PKI) clients and Certificate
Authority (CA) servers can use to support certificate
life cycle operations such as certificate enrollment and revocation,
and certificate and Certificate Revocation List (CRL)
access.
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Single Sign-On (SSO)
An authentication process in a client/server
relationship where the user, or client, can enter one name and password
and have access to more than one application or access to a number of
resources within an enterprise. Single Sign-On removes the need for
the user to enter further authentications when switching between applications.
Learn about Quest's Vintela Single
Sign-On for Java solution.
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smart card
A credit card sized device with embedded microelectronics circuitry
for storing information about an individual.
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S/MIME
S/MIME (Secure Multi-Purpose Internet Mail Extensions) is a secure
method of sending e-mail that uses the RSA encryption
system. S/MIME is included in the latest versions of the Web browsers
from Microsoft and Netscape and has also been endorsed by other vendors
that make messaging products. RSA Security, Inc. has proposed S/MIME
as a standard to the Internet Engineering Task Force (IETF). An alternative
to S/MIME is PGP/MIME, which has also been proposed as a standard.
MIME itself, described in the IETF RFC 1521, describes how an electronic
message will be organized. S/MIME describes how encryption information
and a digital certificate can be included as part
of the message body. S/MIME follows the syntax provided in the Cryptographic
Message Syntax (CMS).
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sockets
Sockets are a method for communication between a client program and
a server program in a network. A socket is defined as "the endpoint
in a connection". Sockets are created and used with a set of programming
requests (function calls) sometimes called the sockets API. The most
common sockets API is the Berkeley UNIX C interface for sockets. Sockets
can also be used for communication between processes within the same
computer.
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SPNEGO
See Simple and Protected GSS-API Negotiation Mechanism
(SPNEGO).
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SSL
See Secure Sockets Layer (SSL).
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SSO
See Single Sign-On.
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stream cipher
An encryption method that works with continuous
streams of input rather than fixed blocks. Contrast with block
cipher.
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symmetric cryptography
Encryption where the same key is used to both encrypt and decrypt data.
This can cause problems unless a secure method for transferring the
key along with the encrypted data can be found. Also referred to as
private key cryptography.
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strong encryption
A term given to describe a cryptosystem that uses a key of sufficient
length that it becomes effectively impossible to break the cipher within
a meaningful time frame.
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ticket
For the Kerberos protocol, a set of electronic
credentials that verifies the identity of a client for a particular
service.
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Ticket-Granting Service
The portion of the Key Distribution Center (KDC)
that issues tickets for specific services. The
user process communicates with the TGS via a Ticket-Granting
Ticket (TGT). See Kerberos.
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Ticket-Granting Ticket
A special Kerberos ticket
that permits the client to obtain additional Kerberos tickets transparently.
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TLS
See Transport Layer Security (TLS).
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token
A security token (sometimes called an authentication
token) is a small hardware device that the owner carries to authorize
access to a network service. The device may be in the form of a smart
card or may be embedded in a commonly used object such as a key fob.
Security tokens provide an extra level of assurance through a method
known as two-factor authentication: the user
has a personal identification number (PIN), which authorizes them as
the owner of that particular device; the device then displays a number
which uniquely identifies the user to the service, allowing them to
log in. The identification number for each user is changed frequently,
usually every five minutes or so.
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Transport Layer Security (TLS)
Transport Layer Security (TLS) is a protocol that ensures privacy
between communicating applications and their users on the Internet.
When a server and client communicate, TLS ensures that no third party
may eavesdrop or tamper with any message. TLS is the successor to the
Secure Sockets Layer (SSL).
TLS is composed of two layers: the TLS Record Protocol and the TLS
Handshake Protocol. The TLS Record Protocol provides connection security
with some encryption method such as the Data Encryption
Standard (DES). The TLS Record Protocol can also be used without
encryption. The TLS Handshake Protocol allows
the server and client to authenticate
each other and to negotiate an encryption algorithm and cryptographic
keys before data is exchanged.
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Triple DES
Triple DES uses three applications of the Data Encryption
Standard (DES) cipher in EDE (Encipher-Decipher-Encipher) mode with
totally independent keys. Sometimes referred to as DESede.
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Trusted Computing Base (TCB)
The totality of protection mechanisms within a computer system—including
hardware, firmware and software—the combination of which are responsible
for enforcing a security policy.
A TCB consists of one or more components that together enforce a unified
security policy over a product or system.
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two-factor authentication
Authentication based on something you
know (for example, a password) and something you have (for example,
a token).
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X.509
A widely used specification for digital certificates
that has been a recommendation of the ITU since 1988.
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XOR
XOR (eXclusive OR) is a bitwise operator that returns a true value
if one, but not both, of its operands is true. XOR is equivalent to
the mathematical operation addition modulo 2.
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