Wednesday, March 5, 2014

Authenticated Encryption vs. Symmetric Encryption

Authenticated Encryption(AE) is a form of Symmetric Encryption. The goal of authenticated encryption is to encrypt or conceal the data as well as confirm the identity of the sender. However, I do not think the situation calls for confirmation of the receiver. Symmetric Encryption does not imply authentication. Therefore, a tag must be added at the end of Symmetric Encryption messages. The tag will then be MACed. So AE is actually a combination of Symmetric Encryption and Message Authentication Codes (MACs).

AE can be implemented using Symmetric Block Ciphers but there are also various other ways to implement it, too. The difference in AE and plain block ciphers is an extra block cipher at the end of AE which is hashed using different inputs. This extra block cipher with a different key makes it that much harder for an adversary to break the encryption of the chain of block ciphers.