Encryption Algorithms...

RSA in 1977 this was first proposed by three mathematitions, this system uses the public and private key format. RSA is the most common form of encryption today.

DES the data encryption standard also founded in 1977, it forms the basis for ATM PIN authentication and also UNIX password encryption, due to recent advances some people think that DES in no longer a safe against all attacks so there has been a stronger standard come out called 3DES, triple DES encrypts three times and uses a different key for at least one of the passes giving it a key size of 122-168 bits.

Blowfish is a symmetric block cypher takes a variable length key from 32 bits to 448, Blowfish was designed in 1993 as free alternative.

IDEA International Data Encryption Algorithm was developed in switzerland in to 1990's it uses the same key encryption/decryption as the DES but uses 128 bit key making it nearly impossible to crack, it also has hardware chipsets to make it even faster.

RC4 is a cypher containing 2048 bits which is reasonably fast in comparison to some methods, it streams a mixture of random bytes and text, it is useful for a situation where a different key can be used for a message.