Re: Got Plaintext and Ciphertext ... Want Algorithm

Steve wrote:
Hey,

If I have a list of plaintext and its associated ciphertext, what is the
best way to go about discovering the algorithm that is used to convert
from one to the other?

This is sci.crypt, not rec.puzzles. It could be
reduce(key1+sha1(input||key2))) for some key1 and key2 that are
infeasable to find. It could be some other complicated thing. It could
be a very weak reduced RC2, but from such few input we couldn't tell.

Also, I'm not quite up to this stage yet, but if I have a tcp stream
segment, and I know for a fact much of its content, whats the best
method to decrypt it?

None. The best what you can do is to tell what encryption was used by
decoding the packet, reading the relevant header values and maybe
reassembling the entire stream, putting it into a context.
.

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