Circom Compatible Poseidon Hash

This crate contains a custom rust implementation of the Poseidon hash function, which is compatible with Circom. Currently, only the parameters for Poseidon with statesizes t=3 (allows hashing two field elements) and t=4 (allows hashing three field elements) for the BN254 curve is present. However, different parameters can be generated with the src/bn254/parameters.sage script, which is a modified copy of the original Poseidon instance generation script from https://extgit.iaik.tugraz.at/krypto/hadeshash/-/blob/master/code/generate_parameters_grain.sage.

Usage (for the BN254 curve):

sage parameters.sage 1 0 254 <t> 8 <r> 0x30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f0000001

where t is the statesize and r is the number of rounds. Circom uses the following round numbers for different statesizes t:

t	r
2	56
3	57
4	56
5	60
6	60
7	63
8	64
9	63
10	60
11	66
12	60
13	65
14	70
15	60
16	64
17	68

Verifying commitments for the Guessing game

One can recalculate the commitment for the guessing game by using the commitment.rs binary in this crate. For a guess G with the randomness R (as hex string) and the address A (as hex string), one can calculate the commitment as:

cargo run --release --bin commitment -- --guess <G> --rand <R> --address <A>

Example:

cargo run --release --bin commitment -- --guess 5 --rand 0xa --address 0x70997970c51812dc3a010c7d01b50e0d17dc79c8