Puzzle Hints

Hint #1

The secret is located in a cell in the advice column of index 1 at position 3, and you have 64 evaluations of it. These are the columns that are related to hashing the secret using Poseidon and they do not depend on the nonce.

Hint #2

Try adding these two lines:
> println!("verifier x: {:?}", *x);
> println!("verifier eval: {:?}", advice_evals[0][1]);
in ./halo2/halo2_proofs/src/plonk/verifier.rs file and think if the printed values can be useful for extracting the secret.

Hint #3

Use the evaluations from the previous hint and the following interpolation function:
> use halo2_proofs::arithmetic::lagrange_interpolate;
> let coeffs = lagrange_interpolate(&xs, &evals);
to reconstruct the polynomial. Then evaluate it in w^2 for
> let w = Fr::from_str_vartime("12799441450189702121232122059226990287081568291547011007819741462284200902087").unwrap();

The winner of the "Best Write-up" prize is piomiko. You can view the solution and puzzle write-up here. The background material required to solve the puzzle is also covered in the write up.
There were many interesting write-up submissions which are linked below:
* Winning write-up by piomiko
* Write-up by niooss-ledger
* Write-up by 10to4
* Write-up by 0x6980
* Write-up by huy-tn
* Write-up by Jasleen1