[rc5] Suggestion for protocol
rskpci at cis.rit.edu
Tue Jun 24 19:43:45 EDT 1997
On Tue, 24 Jun 1997, Remi Guyomarch wrote:
> Fedor Kouranov wrote:
> > Ahem... what's iv?
> Inversion Value ? Well, I don't know ;-)
IV is the ``initialization vector'' for some modes you can run a block
cipher in. For example, the RSA contests use the RC5 algorithm in Cipher
Block Chaining mode, or CBC for short.
CBC is really simple: every block of plaintext to be encrypted is first
XOR'd with the ciphertext from the last block.
The IV is the ``fake'' ciphertext used in the XOR when the very first
block of plaintext is to be encrypted. When you're encrypting that first
block, there is no ``previous block's ciphertext'' to draw on. So, the IV
is used in its place.
In short, it's just a random word chosen at encryption time.
// Bob Krzaczek <http://www.cis.rit.edu/~rskpci/>
// Center for Imaging Science, RIT <rskpci at cis.rit.edu>
To unsubscribe, send email to majordomo at llamas.net with 'unsubscribe rc5' in the body.
More information about the rc5