S-HTTP - Secure HyperText Transfer Protocol, a secure way of transferring information over the World Wide Web.

S/MIME - Secure Multipurpose Internet Mail Extensions.

SSL - Secure Socket Layer. A protocol used for secure Internet communications.

salt - A string of random (or pseudorandom) bits concatenated with a key or password to foil precomputation attacks.

secret key - In secret-key cryptography, this is the single key used both for encryption and decryption. Also called symmetric key. DES is a secret key algorithm

secret sharing - Splitting a secret (e.g. a private key) into many pieces such that any specified subset of N pieces may be combined to form the secret.

secure channel - A communication medium safe from the threat of eavesdroppers.

seed - A typically random bit sequence used to generate another, usually longer pseudorandom bit sequence.

self-shrinking generator - A stream cipher where the output of an LFSR is allowed to feed back into itself.

self-synchronous - Referring to a stream cipher, when the keystream is dependent on the data and its encryption.

session key - A key for symmetric-key cryptosystems which is used for the duration of one message or communication session.

SET - Secure Electronic Transaction. MasterCard and Visa developed (with some help from the industry) this standard jointly to insure secure electronic transactions.

shared key - The secret key two (or more) users share in a symmetric-key cryptosystem.

shrinking generator - A stream cipher built around the interaction of the outputs of two LFSRs. See also stream cipher and linear feedback shift register.

Skipjack - The block cipher contained in the Clipper chip designed by the NSA.

SMPT - Simple Mail Transfer Protocol.

smartcard - A card, not much bigger than a credit card, that contains a computer chip and is used to store or process information.

special-purpose factoring algorithm - A factoring algorithm which is efficient or effective only for some numbers. See also factoring and prime factors.

standards - Conditions and protocols set forth to allow uniformity within communications and virtually all computer activity.

stream cipher - A secret-key encryption algorithm that operates on a bit at a time.

stream cipher based MAC - MAC that uses linear feedback shift registers (LFSR's) to reduce the size of the data it processes.

strong prime - A prime number with certain properties chosen to defend against specific factoring techniques.

sub key - A value generated during the key scheduling of the key used during a round in a block cipher.

S/WAN - Secure Wide Area Network

symmetric cipher - An encryption algorithm that uses the same key is used for encryption as decryption.

symmetric key - See secret key.

synchronous - A property of a stream cipher, stating that the keystream is generated independently of the plaintext and ciphertext.

tamper resistant - In cryptographic terms, this usually refers to a hardware device that is either impossible or extremely difficult to reverse engineer or extract information from.

TCSEC - Trusted Computer System Evaluation Criteria.

threshold cryptography - Splitting a secret (for example a private key into many pieces such that only certain subsets of the N pieces may be combined to form the secret.

timestamp - See digital timestamp

trap door one-way function - A one-way function that has an easy-to-compute inverse if you know certain secret information. This secret information is called the trap door.

trustees - A common term for escrow agents.

verification - The act of recognizing that a person or entity is who or what it claims to be.

Vernam cipher - See one-time pad.

weak key - A key giving a poor level in security, or causing regularities in encryption which can be used by cryptanalysts to break codes.

WWW - World Wide Web.

XOR - A binary bitwise operator yielding the result one if the two values are different and zero otherwise.

zero knowledge proofs - An interactive proof where the prover proves to the verifier that he or she knows certain information without revealing the information.