[Cryptography] a question on consensus over algorithmic agility

[Peter Fairbrother]

On 26/06/14 11:33, ianG wrote:
> Just to separate the meta-notion of consensus from the precise argument
> at hand, here is response in separate cover.  Shooting from the rough,
> take cover!
>
>
>
> On 25/06/2014 23:53 pm, Stephen Farrell wrote:
[...]
> Take your favourite two block ciphers.  Independent keys, XOR the
> output.  This provides the strength of both, together.


For a keyed hash, maybe [1] - but for a cipher, how do you decrypt?


[1] though not necessarily - both inputs for the XOR are derived from 
the same plaintext. It's the same problem for a cascaded cipher - it is 
highly likely that the cascade is stronger than either cipher, but not 
necessarily so.

See M. Maurer and J. L. Massey, Cascade ciphers: The importance of being 
first, Journal of Cryptology, vol. 6, no. 1, pp. 55–61, 1993.

-- Peter Fairbrother