Glossary of some common key algorithms

CAST - A cipher algorithm somewhat similar to DES. This 64-bit symmetric block cipher was developed by C.M. Adams and S.E. Tavares.

CSP - Physically, each Crypto Service Provider is a dynamic-link-library (DLL) with an associated cryptographic signature authorizing it for use by the CryptoAPI. The job of the CSP, such as the two employed by the Navaho privacy Series, is to protect private key information from being exposed.

DES (Data Encryption Standard): A block cipher created by IBM and endorsed by the U.S. government in 1977. Uses a 56-bit key and operates on block of 64 bits. Relatively fast and used to encrypt large amounts of data at one time.

Triple DES: Based on DES. Encrypts a block of data three times with three different keys. Being proposed as an alternative to DES, since it's been said that the potential of easily and quickly cracking DES is increasing every day

Diffie-Hellman: The oldest public-key cryptosystem still in use. Does not support either encryption or digital signatures. System is designed to allow two individuals to agree on a shared key, even though they only exchange messages in public.

DSA: Digital Signature Algorithm, developed by NIST (National Institute of Standards and Technology) based on what's called the El Gamal algorithm. The signature scheme uses the same sort of keys as Diffie-Hellman and can create signatures faster than RSA. Being pushed by NIST as DSS, the Digital Signature Standard, although its acceptance is far from assure. .

DSS - Digital Signature Standard. This standard uses the Digital Signature Algorithm (DSA), a public-key cipher used to generate digital signatures

IDEA (International Data Encryption Algorithm): Created in 1991, it was designed to be efficient to compute in software. Offers very strong encryption using a 128-bit key. .

KEA - Key Exchange Algorithm. This is an improved version of DH (Diffie-Hellman).

MD2 - A hashing algorithm that produces a 128-bit hash value.

MD4 - A hashing algorithm that produces a 128-bit hash value.

MD5 - An improved version of MD4, it is a hashing algorithm that produces a 128-bit hash value.

RC2 - A 64-bit symmetric block cipher.

RC4 - A symmetric stream cipher.

RSA - RSA Public-key Cipher. A popular public key cipher used for both encryption and signatures.

Public Key Algorithms - In the Public Key arrangement the algorithms (asymmetric) use two different keys: the public and the private key. The owner of this key pair keeps the private key private and distributes the public key to anyone who requests it. Public key algorithms are very slow, on the order of 1000 times slower than symmetric algorithms. Consequently, they are normally used only to encrypt session keys. They are also used to digitally sign messages. One of the most common public-key algorithm is the RSA Public-Key Cipher.

SHA - Secure- Hash Algorithm. This is a hashing algorithm that produces a 160 bit hash value.

Skipjack - A symmetric block cipher with a fixed key length of 80 bits. Note it is used in the Clipper chips.

Stream - In a Stream cipher algorithm data is encrypted one bit a time. A stream of plain-text bits flows in one side, and a stream of encrypted cipher-text flows out the other. Stream ciphers in general do not have the strength of block ciphers.

Symmetric Algorithms - Symmetric algorithms are the most common form or encryption techniques. The cipher algorithms are known as symmetric because the same key is used for both encryption and decryption. One of the best features of symmetric keys (unlike public keys) is the ease at which they can be changed, a fact that leads to their also being called session keys. Also, compared to public-key algorithms, symmetric algorithms are very fast and, thus, are the preferred method when dealing large amounts of data. Some of the more common symmetric algorithms are RC2, RC4, and the Data Encryption Standard (DES).