Data Encryption System

Based on the IBM techniques the National Bureau of Standards (USA) developed standard cipher system for commercial use named as DES - Data Encryption System. 64/128 bit key encryption make decoding difficult in DES. Still, it can be cracked by today's powerful PCs connected parallelly equipped with special softwares. Bigger the key, stronger is the
encryption. For most secure transaction, use 512 bit key.

RSA public key crypto system uses different keys for encryption and decryption. In RSA system key used for coding is called public key as it is available to public while the key used for decoding is a secret one - private key. As RSA is too slow (coding and decoding), so it is used to code the key of DES.

Cryptographic algorithms

Symmetric key : IDEA, DES, Tripple DES, Blowfish, RC4, RC5 etc.
Public key : RSA, Elgamal, DSS, Diffie-Hellman key exchange, MD5, SHA etc.

Cryptographic systems in use for E-mail are Secure Socket Layer (SSL), Pretty Good Privacy (PGP), Multipurpose Internet Mail Extensions (MIME) etc.