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Re: Multiple symetric cyphers



On Thu, 12 Jan 1995, Paul Robichaux wrote:

> > But selecting a single cipher is just as much a fixed policy as a
> > randomly selected one is.  Far better to let the user pick a policy,
> > both about sent and accepted ciphers.
> 
> If you do give the user control, what is an acceptable mechanical
> implementation? Let's say I have a file encryptor which allows the
> user to choose between DES, 3DES, IDEA, Diamond, and RC5. Must I
> require the user to tell that program what cypher was used to encrypt
> the file she wishes to decrypt?
> 
> Is storing the cypher type as part of the encrypted file a weakness?

Perhaps it is.  The algorithm set could be part of the key, though...