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Glossary of Terms (Page 5) |
lattice - A lattice can be viewed as an N-dimensional 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. meet-in-the-middle 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 fixed-length output. See also hash-based MAC, stream-cipher based MAC, and block-cipher based MAC. message digest - The result of applying a hash function to a message. MHS - Message Handling System. middle-person 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. MIPS-Year - 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. non-repudiation - A property of a cryptosystem. Non-repudiation 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 security-conscious U.S.government agency whose mission is to decipher and monitor foreign communications. number field sieve - A method of factoring, currently the fastest general-purpose factoring algorithm published. It was used to factor RSA-130. 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. one-time pad - A secret-key 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. one-way function - A function that is easy to compute in one direction but quite difficult to reverse compute (compute in the opposite direction). one-way hash function - A one-way function that takes a variable sized input and creates a fixed size output. |