Quor's cipher

[Matthew Ghio]

Antonomasia <ant at notatla.demon.co.uk> wrote:

> How are you planning to detect which bytes are passed in this way ?
> Chosen plaintext attacks would do it, and show where (a+b)^(a0+b0) == 0.
> Looks like you've just doubled our progress.

It doesn't take chosen plaintext, just known plaintext.

> 
> If the key is reused with a different message I don't think there's a
> weakness.  An IV is a good idea, but aren't we _attacking_ this thing ?

Lack of an IV is a problem with almost any cipher, but it seems especially
so here.