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Re: triple DES
Ashar Aziz says:
> The way we do this is to do Encrypt-Decrypt-Encrypt with three
> keys in ECB mode, and use the resulting ECB cipher in CBC
> mode. One can also do 2-key triple DES, where the first and
> last encryption keys are the same, the decryption key being
> different. Note that if all three keys are the same, you
> effectively get single encryption DES (at roughly one-third
> the speed).
In general, you want this feature last feature when you are in a
hardware implementation emulating ordinary DES with 3DES hardware (and
this has in fact been done) so it isn't entirely nonsensical to do
it. BTW, all three keys don't have to be the same -- just k1 and k2 or
k2 and k3, though in practice there is no reason not to just make them
all the same.
Perry
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