Multiple symetric cyphers

[Paul Robichaux]

> 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?

-Paul

-- 
Paul Robichaux, KD4JZG       | Good software engineering doesn't reduce the 
perobich at ingr.com            | amount of work you put into a product; it just 
Not speaking for Intergraph. | redistributes it differently.
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