
DiffieHellman key exchange algorithm  First published public key algorithm, can be used only for exchanging keys  Uses recipient’s public key to generate a secret key; public data is then sent to recipient who can now generate the secret key 

DSA (digital signature algorithm)  Does not encrypt data, but produces a signature that can be verified A public key (of 3 parts) is calculated from a private key  Signing: input is data to be signed, private key, a random number; output is a signature, comprising 2 numbers called r & s Verifying: input is data to be verified, public key & s; output is a number called v; if v = r then signature is verified 

SHA (secure hash algorithm)  US government standard produced by NIST Based on MD4 algorithm. Revised version of 1995 called SHA1  Takes a message of less than 2^{64} bits and produces a message digest/fingerprint of 160 bits 

DSS (digital signature standard)  US government standard method  Uses DSA to sign a message digest/fingerprint produced by SHA 

ElGamal (T ElGamal’s algorithm)  Variant of DiffieHellman for encryption and decryption as well as key exchanges  Sometimes known as DiffieHellman in earlier versions of PGP 

RSA (RivestShamirAdleman algorithm)  First main, and still, the most widely used general purpose publickey encryption algorithm  Encrypt message with public key to obtain confidentiality Encrypt message with private key to obtain authentication, integrity, and nonrepudiation 

3DES triple DES (data enrcyption standard)  DES was the first widespread symmetric key encryption algorithm 3DES applies the algorithm 3 times for additional security  DES is a 56bit key, 64bit block cypher using multiple rounds of permutations and substitutions Now considered necessary to apply 3 times with 3 keys 

CAST128 (developed by Carlisle Adams and Stafford Tavares)  Modern symmetric key encryption algorithm CAST128 is an implementation of the CAST design procedure  Uses key sizes of 40 to 128 bits (in 8bit increments) with 16 rounds of 64bit blocks of plaintext Has been extensively reviewed by cryptologists 

IDEA (international data encryption algorithm)  Modern symmetric key encryption algorithm, designed as a replacement for DES  128bit key block cypher encrypting 64bit blocks of plaintext 

AES/Rijndael (Daemen and Rijmen’s algorithm)  Selected for the new “Advanced Encryption Standard” by NIST to replace DES  High performance and very secure algorithm, using key sizes of 128, 192, and 256 bits 

RSA  Selected for the new “Advanced Encryption Standard” by NIST  High performance and very secure algorithm 
