[Cryptography] Can you backdoor a symmetric cipher

[Perry E. Metzger]

On Thu, 5 Sep 2013 21:42:29 -0700 Jon Callas <jon at callas.org> wrote:
> On Sep 5, 2013, at 9:33 PM, "Perry E. Metzger" <perry at piermont.com>
> wrote:
> 
> > 
> > It is probably very difficult, possibly impossible in practice, to
> > backdoor a symmetric cipher. For evidence, I direct you to this
> > old paper by Blaze, Feigenbaum and Leighton:
> > 
> > http://www.crypto.com/papers/mkcs.pdf
> > 
> 
> There is also a theorem somewhere (I am forgetting where)

See the URL quoted above. That is the implication of their paper.

> that says that if you have a block cipher with a back door, then it
> is also a public key cipher.

Perry
-- 
Perry E. Metzger		perry at piermont.com