Re: Maybe we only need PCBC...

From: Mok-Kong Shen (mok-kong.shen_at_t-online.de)
Date: 06/29/03 

Date: Sun, 29 Jun 2003 12:43:35 +0200

jsavard@ecn.ab.ca wrote:
>
> It occurred to me that my recent invention, PCC mode encryption, even
> though it is much simpler than other integrity-aware schemes, instead of
> being what the world is looking for, may still be overly complex.
>
> PCBC mode encryption was one of the first attempts at an integrity-aware
> encryption mode. But it had a defect; one could exchange blocks, and then
> the result would be to garble a small portion of the message, with the
> rest remaining intact.
[snip]

>From the diagram at your webpage
 
    http://home.ecn.ab.ca/~jsavard/crypto/co040603.htm

I understand that you use both the plaintext and the
ciphertext of the previous block to xor with the current
plaintext block before performing the proper encryption.
I have employed a similar idea, using though the sum of
'all' previous plaintext and ciphertext blocks to do
the xor. See my design WEAK3-EX on my old webpage (recently
being completely replaced with another stuff):

  http://home.t-online.de/home/mok-kong.shen/oldwebpage.htm

I once also suggested in the group the use of a non-linear
version of that.

M. K. Shen