## Cryptography for everybody: Zero-Knowledge Proofs and Protocols Explained

In my newest video on “Cryptography for everybody”, I explain how zero-knowledge proofs and protocols work. A zero-knowledge proof or protocol is a method by which one party (usually Peggy P) can prove to another party (usually the verifier Victor V) that they know a value (e.g. a secret key or password) without actually revealing it.

First, we discuss the classical cave example by Quisquater: Here, Peggy wants to prove to Victor that she knows how to open a secret door in a cave. But only to Victor and not to anyone else.

Then, we have a look at a real zero-knowledge protocol: the Fiat-Shamir Protocol. This protocol works with modular arithmetic. Peggy has to create a private key s and register her public key v = s² with a trusted third party. Then, Victor can challenge her with a simple protocol. How this works, I explain in the video.

Finally, we have a look at the zero-knowledge simulation in CrypTool 2. Watch the video here:

“Cave” paper by Quisquater: Quisquater, Jean-Jacques, et al. “How to explain zero-knowledge protocols to your children.” Conference on the Theory and Application of Cryptology. Springer, New York, NY, 1989.

Feige-Fiat-Shamir protocol: Feige, Uriel, Amos Fiat, and Adi Shamir. “Zero-knowledge proofs of identity.” Journal of cryptology 1.2 (1988): 77-94.