Quote:
Originally Posted by McAllister
RogerBW's assertion implies that TL(N) cryptanalysis cannot reliably break TL(N) cryptography
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Actually, it doesn't. His assertion is that higher tech cryptanalysis can defeat lower tech encryption. That statement in itself says nothing about equal tech levels. He didn't assert that _only_ higher tech can defeat encryption.
An important part of the tech advance in this case is in mathematics, not just speed of computation. Historical cryptosystems tend to fail when someone figures out a new method for attacking them, whether that's letter and n-graph frequencies for substitution ciphers or differential cryptanalysis.
Copy protection is a bit different than encryption in that the protected system has to be capable of decrypting itself. So, it contains any necessary keys, algorithms, and a way to trigger execution. An encrypted message keeps those separated. So, the strength of the copy protection doesn't rely on just the strength of the cipher used. They have the additional weakness of securing the whole system, which is usually the weaker link in the chain. (Analogies for encryption might be bribing the legitimate recipient to give you the contents of the message, or ignoring the encrypted email transmission and just copying the data from the receiving network switch after it's been decrypted.)
I'm not sure if this kind of attack is really Cryptography skill or one of the relevant Engineering skills (whether mechanical, computer, or social engineering).