Jonathan Katz
Sun, 29 Jun 2008 14:08:52 -0700
On Fri, 27 Jun 2008, Erik Ostermueller wrote:
Hello all, If I exchange messages with a system and the messages are encrypted with a symmetric key, what further benefit would we get by using a MAC (Message Authentication Code) along with the message encryption? Being new to all this, using the encrytpion and MAC together seem redundant. Thanks, --Erik Ostermueller
As the other posters have already commented, encryption alone does not (in general) provide integrity. Furthermore, care must be taken in how the encryption scheme and the MAC are combined, with encryption-followed-by-MACing-the-ciphertext being the best choice unless you know what you are doing. For further discussion, see the textbook by Katz-Lindell (Section 4.9), and/or the following paper: http://www-cse.ucsd.edu/users/mihir/papers/oem.html --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]