[cryptography] Devised a Change to RC4

Ryan Carboni ryacko at gmail.com
Wed Aug 20 22:30:37 EDT 2014


The biases with RC4 derived ciphers have to deal with the unlikelihood that
an equivalent value (usually zero) will occur near another in the first few
bytes of every 256 byte block.

Each byte is equally probable of occurring, though. By randomly permuting
the bytes, and scrambling the permutation array after each block, it
removes the bias. The original keystream should be sufficiently random to
scramble it.

I call it a self-scrambling generator and the core concept could be paired
with any stream cipher.

Might reduce the strength of some related key attacks.

I'm interested if a person can show a distinguishing attack against this.

On Wed, Aug 20, 2014 at 3:40 AM, Jeffrey Walton <noloader at gmail.com> wrote:

> On Wed, Aug 20, 2014 at 4:39 AM, Ryan Carboni <ryacko at gmail.com> wrote:
> > Feed RC4 through a transposition cipher... essentially a single round
> > 2048-bit block cipher.
> >
> > Table 1: 256 permuted bytes, serves as the PRGA
> > Table 2: 256 permuted bytes, serves as the transposition cipher
> > Table 3: 256 empty values, serves as the output array
> > Table 4: 256 empty values, serves as the output array to rescramble the
> > transposition cipher
> > ...
> >
> > Just wondering if it's a good change.
> Wouldn't you still have the same biases, but in different places?
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.randombit.net/pipermail/cryptography/attachments/20140820/a0b49309/attachment.html>


More information about the cryptography mailing list