How to add unused public signals in circom

sir assistant

11/18/23, 3:31 PM

In my usecase, i want to attach a public key to a proof generated by a circom circuit. If my circuit is like follows:

template Example() {
  signal input secret;
  signal input hash;
  signal input salt;

  signal output verified;

  // Hash the secret and the salt, compare it to hash and assign it to the verified output
  // Omitted for brevity
}

component main {public [hash]} = Example();

If i just generate a proof that i know the secret and the salt, and then sign it, other party can take the proof and sign it with a different key without knowing the secret, defeating the purpose.

Would it be possible to add a public key to the inputs, even though it's unused in the circuit in a way that nobody can generate a proof swapping the public key with other different key without knowing the secret?

template Example() {
  signal input secret;
  signal input hash;
  signal input salt;
  signal input publicIdentity; // Unused

  signal output verified;

  // Hash the secret and the salt, compare it to hash and assign it to the verified output
  // Omitted for brevity
}

component main {public [hash, publicIdentity]} = Example();

Do I need to add a artificial constraint like publicIdentity * 0 === 0? If so, why?

0 + 0

zero-knowledge-proofs

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Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: How to add unused public signals in circom

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