Glossary of Terms (Page 3)
Data Encryption Standard  See DES.
decryption  The inverse (reverse) of encryption.
DES  Data Encryption Standard, a block cipher developed by IBM and the U.S. government in the 1970's as an official standard. See also block cipher.
dictionary attack  A brute force attack that tries passwords and or keys from a precompiled list of values. This is often done as a precomputation attack.
DiffieHellman key exchange  A key exchange protocol allowing the participants to agree on a key over an insecure channel.
differential cryptanalysis  A chosen plaintext attack relying on the analysis of the evolution of the differences between two plaintexts.
digest  Commonly used to refer to the output of a hash function, e.g. message digest refers to the hash of a message.
digital envelope  A key exchange protocol that uses a publickey cryptosystem to encrypt a secret key for a secretkey cryptosystem.
digital fingerprint  See digital signature.
digital signature  The encryption of a message digest with a private key.
digital timestamp  A record mathematically linking a document to a time and date.
discrete logarithm  Given two elements d, g, in a group such that there is an integer r satisfying g ** r = d, r is called the discrete logarithm.
discrete logarithm problem  The problem of given d and g in a group, to find r such that g ** r = d. For some groups, the discrete log problem is a hard problem that can be used in publickey cryptography.
distributed key  A key that is split up into many parts and shared (distributed) among different participants. See also secret sharing.
DMS  Defense Messaging Service.
DOD  Department of Defense.
DSA  Digital Signature Algorithm. DSA is a publickey method based on the discrete log problem.
DSS  Digital Signature Standard. DSA is the Digital Signature Standard.
ECC  Elliptic Curve Cryptosystem; A publickey cryptosystem based on the properties of elliptic curves.
ECDL  See elliptic curve discrete logarithm.
EDI  Electronic (business) Data Interchange.
electronic commerce (ecommerce)  Business transactions conducted over the Internet.
electronic mail (email)  Messages sent electronically form one person to another via the Internet.
elliptic curve  The set of points (x,y) satisfying an equation of the form y ** 2 = x ** 3 + ax + b, for variables x, y and constants a, b.
elliptic curve cryptosystem  See ECC.
elliptic curve discrete logarithm (ECDL) problem  The problem of given two points P and Q on an elliptic curve, to find m satisfying mP = Q, assuming such and m exists.
elliptic curve (factoring) method  A specialpurpose factoring algorithm that attempts to find a prime factor p of an integer n my finding an elliptic curve shows number of points modulo p is divisible by only small primes.
encryption  The transformation of plaintext into an apparently less readable form (called ciphertext) through a mathematical process. The ciphertext may be read by anyone who has the key that decrypts (undoes the encryption) the ciphertext.
exclusive or  See XOR.
exhaustive search  Checking every possibility individually till the right value is found. See also attack.
expiration date  Certificates and keys may have a limited lifetime; expiration dates are used to monitor this.
exponential function  A function where the variable is in the exponent of some base, for example, b ** N where N is the variable, and b is some constant.
export encryption  Encryption, in any form, which leaves its country of origin. For example, encrypted information or a computer disk holding encryption algorithms that is sent out of the country.
