The symmetric ciphers

[Philipp Klaus Krause]

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Am 10.09.2013 12:35, schrieb Philipp Klaus Krause:
> I wonder if it would be a good idea to have an option to combine 
> symmetric ciphers, e.g. users could state a preference list like
> this:
> 
> TWOFISH+AES256 3DES+BLOWFISH+AES AES 3DES
> 
> The meaning of A+B would be to encrypt using A first, and then
> encrypt the result using B with a different key. Assuming it takes
> effort a to break cipher A and effort b to break cipher b, this
> should result in effort at least max(a, b) needed to break A+B. And
> with uncertainity about possible weaknesses in individual ciphers,
> this seems like a reasonable measure to me.
> 
> Philipp

If we have plenty of randomness available, we could do this a
different way:
XOR the message M with a random one-time pad P to obtain N. Encrypt P
with A, and N with B.
The drawback is that this doubles the lenth of the message.

Philipp
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