Are you tired of having to reveal the solution to your sudoku in order to convince others that you have solved it? Are you sick of not being believed when you know a secret? Are you embarrassed about your id card picture and having to expose it every time you need to prove your identity?

For the third: Sorry… For the former two: Here they come! Zero-Knowledge proof systems!

A ZK proof system allows a party (the prover) to convince another party (the verifier) about the validity of certain statement, without revealing any other additional information, e.g., why the statement is valid. ZK proofs play an essential role in many applications such as: authentication systems, cryptographic protocols or blockchains.

In this talk, I will present several examples of ZK proofs and I will consider the following two questions:

• How can we be sure that no additional information is leaked from a proof?
• What does it mean “to know something”?

The audience will get an intuition about how the above questions have been formally addressed in cryptography.