4 ms·

yeah, but it isn't equivalent to FHE, and doesn't seem as strong a guarantee.

by sa1 5y ago

faeyanpiraat 5y ago
There is a difference between an array of encrypted numbers (which fhe requires if I understand it correctly), and a completely encrypted bitstream (where the data could be put to hide the fact that it is a number array)
sterlind 5y ago
it's actually stronger than FHE, which is what I was saying. virtual black-box obfuscation would mean that an attacker could only observe the outputs and the inputs - all intermediate states and data, such as the decrypted inputs or the decryption key or logic - would themselves be encrypted. it's like having FHE with an output decryptor circuit at the end. unfortunately VBB was shown to be impossible, but indistinguishability obfuscation - producing a program that's indistinguishable from any other program that produces the same outputs for the same inputs - is possible, as recently demonstrated. iO is weaker but still useful. imagine that I have a program that looks like "return input == secret". with iO, you couldn't recover the value of "secret" from the program, since "return Hash(input) == HashedSecret" is equivalent to the original, and iO guarantees that all alternate implementations of a function are indistinguishable.
- sa1 5y ago
  I really want to understand this. Let's say my focus is on retrieving the input, not the secret. I do not want the people who are running the program to know my input. I do not want the program to know my input. Does indistinguishability obfuscation help with that?
  - sterlind 5y ago
    if you want the users of the program to know the output, but you want to keep the input a secret, you could use functional encryption (another special case of iO.) users can compute a function of the input without being able to decrypt the input or learn anything else about it. if you want the output to be encrypted too (even potentially with a different key), you can use vanilla FHE.
    - sa1 5y ago
      Thanks, the latter is what I would desire.

yeah, but it isn't equivalent to FHE, and doesn't seem as strong a guarantee.

by sa1 5y ago

yeah, but it isn't equivalent to FHE, and doesn't seem as strong a guarantee.

There is a difference between an array of encrypted numbers (which fhe requires if I understand it correctly), and a completely encrypted bitstream (where the data could be put to hide the fact that it is a number array)

sterlind 5y ago

it's actually stronger than FHE, which is what I was saying. virtual black-box obfuscation would mean that an attacker could only observe the outputs and the inputs - all intermediate states and data, such as the decrypted inputs or the decryption key or logic - would themselves be encrypted. it's like having FHE with an output decryptor circuit at the end. unfortunately VBB was shown to be impossible, but indistinguishability obfuscation - producing a program that's indistinguishable from any other program that produces the same outputs for the same inputs - is possible, as recently demonstrated. iO is weaker but still useful. imagine that I have a program that looks like "return input == secret". with iO, you couldn't recover the value of "secret" from the program, since "return Hash(input) == HashedSecret" is equivalent to the original, and iO guarantees that all alternate implementations of a function are indistinguishable.

sa1 5y ago
I really want to understand this. Let's say my focus is on retrieving the input, not the secret. I do not want the people who are running the program to know my input. I do not want the program to know my input. Does indistinguishability obfuscation help with that?
- sterlind 5y ago
  if you want the users of the program to know the output, but you want to keep the input a secret, you could use functional encryption (another special case of iO.) users can compute a function of the input without being able to decrypt the input or learn anything else about it. if you want the output to be encrypted too (even potentially with a different key), you can use vanilla FHE.
  - sa1 5y ago
    Thanks, the latter is what I would desire.