Crypto Questions

[Markku-Juhani Saarinen]

Peter Fairbrother:
> 2) Does anyone know of a backwards hash, ie an algorithm that gives a
> previously specified result from a cyphertext but which is 
> infeasible to reverse?  How would you generate the cyphertext? No 
> secret keys allowed.

Hi, 

  If I understand this correctly, you are looking for a signature 
  scheme with message recovery.

  The most obvious choice would be to sign the message with RSA
  (without hashing it first). You can throw away the private key
  if you wish.

Cheers,
- mj

Markku-Juhani O. Saarinen <mjos@jyu.fi>  University of Jyväskylä, Finland