Thread by @MantaNetwork

Let’s continue our #WhyZK series:
In our last thread, we used a Sudoku game to explain some terms and the properties of ZK. In this thread, we’ll keep using Sudoku to explain the concept of Interactive Proof and Non-Interactive Proof.

https://twitter.com/MantaNetwork/status/1607735076275601410

Dr. Strange proved that he could solve a Sudoku puzzle without telling Hulk how he solved it. The next day, Hulk said, 'Why don't we live stream the game online?' Dr. Strange thought it was a great idea, so they started a Youtube channel and asked Iron Man to join as ops manager.

Their channel soon drew many followers. One day, Dr. Strange forgot the solution to the puzzle right before live streaming. He had nothing to do but tell Hulk to fake the verification process with him. Iron Man, after witnessing this, was disappointed at this behavior.

Days after, Iron Man came to Dr. Strange and Hulk with a machine. It's a machine that can verify the sudoku puzzles automatically. Once the cards are placed on a moving conveyor belt, the machine can randomly verify Dr. Strange's solutions.

This machine is like a #zkp Simulator. It generates random numbers and chooses a verification approach. But if Iron Man designs the program, he must know the rules and could cheat. Now it's time to introduce Trusted Setup.

When zk-SNARK first initiates, private keys will be generated with the creation of proofs and the verification process, including a Common Reference String. A Trusted Setup is a decentralized way to destroy the CRS and secure the whole scheme.

Every participant in a Trusted Setup will get a piece of the CRS. If at least one person is being honest and destroys their piece of the secret, no one will know the secret key.

In practice, the Trusted Setup Client will automatically delete the public reference string for the user. Completing Trusted Setups often represents the official launch of the zk-SNARK network.

Essentially this: every participant holds a piece of the secret. If one person deletes theirs, the secret key can't be recovered, and the whole scheme will be secured. After completing the Trusted Setup, the verification result of the Simulator becomes trustworthy and reliable.

Non-Interactive Proofs have almost completely replaced Interactive Proofs in the blockchain field. Both zk-SNARK and zk-STARK are Non-Interactive Proofs. Incidentally, zk-STARKs do not require a Trusted Setup to launch the network.

The technical terms are a tricky part of learning ZK. What's the relevance between Halo2, Plonk, Groth16, zk-SNARK, and zk-STARK? We will talk about these technical terms in detail in the next thread.