[mercury-users] functions returning in values?

[MCL]

>> > (youre thinking of one-way hash functions, while ralph was talking
>> > about ciphers, I believe)
>> 
>> um, he actually says "cipher function" explicitly, I notice now

Yes, you are right. I was mislead by the common use of the
"cryptography" term nowadays.  As he explained

   :- pred cipher(key, plaintext, ciphertext).
   :- mode cipher(in, in, out) is det.
   :- mode cipher(in, out, in) is det.

   cipher(K, P, C) :- ...

   and get both directions from the same code, both of which of course
   will require the key as an input.  I was not suggesting that you should
   expect to get a key-cracker out of it.

which basically requires constraint solving capabilities, right?  Hum.
What about getting key out of plaintext and ciphertext?  That would be
much more interesting: if you accidentaly catch the ciphered and clear
versions of the same message, then you might be able to
recreate/enumerate the keys.  

    (Sorry about this late off-topic).

        MCL

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