Bob … is this YOUR signature? Yes. I can prove it, here …
How many times have you watched a movie, and there’s a court scene and where the person is ask, “Is this your signature?”. It’s a standard thing in trust, and where we must make sure that someone has signed something. In the world of digital trust, we normally use the private key to sign for something, and then the public key to prove it. But let’s say that that’s not enough for Alice, and she wants Bob to give her proof that it is his signature. For this, we look for an undeniable proof of a signature.
With an undeniable signatures, Alice requires an interaction with Bob to prove Bob’s signature. In this case we will implement the Chaum-van Antwepen undeniable signature scheme [here][1]:
For this, Bob interacts with Alice to prove that he was the one who signed a message
Key generation
Bob generates two prime numbers (p and q) and where:
p=2q+1
Next Bob selects a random value β and then selects:
Next Bob selects a random value of a from 0 to q−1 , and computes:
