Glossary of Terms (Page 5)
lattice  A lattice can be viewed as an Ndimensional grid.
LEAF  Law Enforcement Agency Field a component in the Clipper Chip.
life cycle  The length of time a key can be kept in use and still provide an appropriate level of security.
linear complexity  Referring to a sequence of 0's and 1's, the size of the smallest linear feedback shift register (LFSR) that would replicate the sequence. See also linear feedback shift register.
linear cryptanalysis  A known plaintext attack that uses linear approximations to describe the behavior of the block cipher. See known plaintext attack.
linear keyspace  A key space where each key is equally strong.
LFSR  linear feedback shift register. Used in many keystream generators because of its ability to produce sequences with certain desirable properties.
MAC  See message authentication code.
meetinthemiddle attack  A known plaintext attack against double encryption with two separated keys where the attacker encrypts a plaintext with a key and "decrypts" the original ciphertext with another key and hopes to get the same value.
Message Authentication Code (MAC)  A MAC is a function that takes a variable length input and a key to produce a fixedlength output. See also hashbased MAC, streamcipher based MAC, and blockcipher based MAC.
message digest  The result of applying a hash function to a message.
MHS  Message Handling System.
middleperson attack  A person who intercepts keys and impersonates the intended recipients.
MIME  Multipurpose Internet Mail Extensions.
MIPS  Millions of Instructions Per Second, a measurement of computing speed.
MIPSYear  One year's worth of time on a MIPS machine.
mixed integer programming  The problem is to solve a linear programming problem where some of the variables are restricted to being integers.
modular arithmetic  a form of arithmetic where integers are considered equal if they leave the same remainder when divided by the modulus.
modulus  The integer used to divide out by in modular arithmetic.
multiple polynomial quadratic sieve (MPQS)  A variation of the quadratic sieve that sieves on multiple polynomials to find the desired relation. MQPS was used to factor RSA  129.
NIST  National Institute of Standard and Technology, a United States agency that produces security and cryptography related standards (as well as others); these standards are published as FIPS documents.
nonrepudiation  A property of a cryptosystem. Nonrepudiation cryptosystems are those in which the users cannot deny actions they performed.
nonlinear keyspace  A key space comprised of strong and weak keys.
NSA  National Security Agency. A securityconscious U.S.government agency whose mission is to decipher and monitor foreign communications.
number field sieve  A method of factoring, currently the fastest generalpurpose factoring algorithm published. It was used to factor RSA130.
number theory  A branch of mathematics that investigates the relationships and properties of numbers.
OAEP  Optimal Asymmetric Encryption Padding; a provably secure way of encrypting a message.
onetime pad  A secretkey cipher in which the key is a truly random sequence of bits that is as long as the message itself, and encryption is performed by XORing the message with the key. This is theoretically unbreakable.
oneway function  A function that is easy to compute in one direction but quite difficult to reverse compute (compute in the opposite direction).
oneway hash function  A oneway function that takes a variable sized input and creates a fixed size output.
