Comment by dist-epoch

Comment by dist-epoch 9 days ago

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> you can observe what CPU instructions it uses to sign the challenge, and replicate the operations yourself.

No you can't, that's the whole thing with homomorphic encryption. Ask GPT to explain it to you why it's so.

You have no way of knowing the bounds of the code I will access from the inside the homomorphic code. Depending on the challenge I can query parts of the binary and hash that in the response. So you will need to replicate the whole binary.

Similar techniques are already used today by various copy-protection/anti-cheat game protectors. Most of them remain unbroken.

fc417fc802 9 days ago

I don't believe this is correct. Homomorphic encryption enables computation on encrypted data without needing to decrypt it.

You can't use the result of that computation without first decrypting it though. And you can't decrypt it without the key. So what you describe regarding memory addresses is merely garden variety obfuscation.

Unmasking an obfuscated set of allowable address ranges for hashing given an arbitrary binary is certainly a difficult problem. However as you point out it is easily sidestepped.

You are also mistaken about anti-cheat measures. The ones that pose the most difficulty primarily rely on kernel mode drivers. Even then, without hardware attestation it's "just" an obfuscation effort that raises the bar to make breaking it more time consuming.

What you're actually witnessing there is that if a sufficient amount of effort is invested in obfuscation and those efforts carried out continuously in order to regularly change the obfuscation then you can outstrip the ability of the other party to keep up with you.

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do_not_redeem 9 days ago

You're just describing ordinary challenge-response. That has nothing to do with homomorphic encryption and there are plenty of examples from before homomorphic encryption became viable, for example https://www.geoffchappell.com/notes/security/aim/index.htm

Homomorphic encryption hides data, not computation. If you've been trying to learn compsci from GPT, you might have fallen victim to hallucinations. I'd recommend starting from wikipedia instead. https://en.wikipedia.org/wiki/Homomorphic_encryption

And btw most games are cracked within a week of release. You have way too much faith in buzzwords and way too little faith in bored Eastern European teenagers.

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  • dist-epoch 9 days ago

    > Homomorphic encryption hides data, not computation

    Data is computation.

      x = challenge_byte ^ secret_key
  if x > 64:
    y = hash_memory_range()
  else:
    y = something_else()
  return sign(y, secret_key)
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    • do_not_redeem 8 days ago

      That snippet has nothing to do with homomorphic encryption. It's just the same kind of challenge-response AIM and many others were already doing in the 90s.

      You seem convinced that homomorphic encryption is some kind of magic that prevents someone from observing their own hardware, or from running Chrome under a debugger. That's just not true. And I suspect we don't share enough of a common vocabulary to have a productive discussion, so I'll end it here.

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