Symmetric Cipher Algos

• In the olden days we had the Caeser cipher a.k.a. ROT-13

• Secrecy was contingent on protecting the algorithm

• Today we have ciphers with open algorithms, say ROT-x

• Secrecy is contingent on protecting the key (say x=13) not the algorithm

• Examples are DES, 3DES, AES, Blowfish

• A single secret/session key is used to encrypt and decrypt data.