If the output of an algorithm when interacting with the [encryption] protocol matches that of a simulator given some inputs, it ‘need not know’ anything more than those inputs.

  • Can a machine learn to find a method to break encryption protocols?
  • How is that possible, to decrypt ciphers using deep learning methods?

1 Answer 1


There is no evidence of deep learning breaking modern cryptography. Deep learning is simply glorified gradient descent. With a reasonable cipher you get no indication of almost finding the key, so I see no hope of deep learning breaking a black box cipher.

In order to use deep learning for cryptography we would need to find a notion of gradually or partially solving the problem, not an easy task.

We have seen some work to use deep learning to build new ciphers, using adversarial training. But there is not much evidence these ciphers are secure against human cryptanalysis.

  • 2
    $\begingroup$ Enigma had 23.5 bits of key entropy. Enigma is security through obscurity. Enigma can't stand against today's standards of security. And I still don't think deep learning can crack Enigma. $\endgroup$ Sep 8, 2018 at 6:38
  • 4
    $\begingroup$ @John Dvorak: How do you come to the conclusion that "Enigma had 23.5 bit of key entropy"? Based on this answer, the M3 with 10 wires on the plugboard had 67.1 bit of key entropy (not counting 14.1 bit for the initial, nominally random rotor position, much like we do not count a random IV in the key entropy of a modern cipher). That source gets 87.5 bit for the M4 with 13 wires. $\endgroup$
    – fgrieu
    Sep 8, 2018 at 9:04
  • 4
    $\begingroup$ @PaulUszak You are comparing apples and oranges. With Go, you can tell when you are winning or losing, and each move gives you feedback. Do you still think deep learning could excel at Go if it wasn't allowed to see the opponent's response or the current board state, and had to win a trillion trillion trillion trillion games in a row before it is able to learn that it has even one a single game? $\endgroup$
    – forest
    Sep 9, 2018 at 2:56
  • 4
    $\begingroup$ Seeing the output isn't likely to produce a meaningfull gradient. It's not that this hasn't been tried. It doesn't work. $\endgroup$
    – Meir Maor
    Sep 9, 2018 at 17:35
  • 3
    $\begingroup$ @JohnDvorak There are still unsolved messages today (from WW2) for Enigma and people have tried to break them with no success.... You still need some luck to break them or long enough messages. So in some cases it's enough. $\endgroup$ Sep 13, 2018 at 21:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.