poseidon-rs/src/lib.rs

extern crate rand;
#[macro_use]
extern crate ff;
use ff::*;

#[derive(PrimeField)]
#[PrimeFieldModulus = "21888242871839275222246405745257275088548364400416034343698204186575808495617"]
#[PrimeFieldGenerator = "7"]
pub struct Fr(FrRepr);

mod constants;

#[derive(Debug)]
pub struct Constants {
    pub c: Vec<Vec<Fr>>,
    pub m: Vec<Vec<Vec<Fr>>>,
    pub n_rounds_f: usize,
    pub n_rounds_p: Vec<usize>,
}
pub fn load_constants() -> Constants {
    let (c_str, m_str) = constants::constants();
    let mut c: Vec<Vec<Fr>> = Vec::new();
    for i in 0..c_str.len() {
        let mut cci: Vec<Fr> = Vec::new();
        for j in 0..c_str[i].len() {
            let b: Fr = Fr::from_str(c_str[i][j]).unwrap();
            cci.push(b);
        }
        c.push(cci);
    }
    let mut m: Vec<Vec<Vec<Fr>>> = Vec::new();
    for i in 0..m_str.len() {
        let mut mi: Vec<Vec<Fr>> = Vec::new();
        for j in 0..m_str[i].len() {
            let mut mij: Vec<Fr> = Vec::new();
            for k in 0..m_str[i][j].len() {
                let b: Fr = Fr::from_str(m_str[i][j][k]).unwrap();
                mij.push(b);
            }
            mi.push(mij);
        }
        m.push(mi);
    }
    Constants {
        c: c,
        m: m,
        n_rounds_f: 8,
        n_rounds_p: vec![56, 57, 56, 60, 60, 63, 64, 63],
    }
}

pub struct Poseidon {
    constants: Constants,
}
impl Poseidon {
    pub fn new() -> Poseidon {
        Poseidon {
            constants: load_constants(),
        }
    }
    pub fn ark(&self, state: &mut Vec<Fr>, c: &Vec<Fr>, it: usize) {
        for i in 0..state.len() {
            state[i].add_assign(&c[it + i]);
        }
    }

    pub fn sbox(&self, n_rounds_f: usize, n_rounds_p: usize, state: &mut Vec<Fr>, i: usize) {
        if i < n_rounds_f / 2 || i >= n_rounds_f / 2 + n_rounds_p {
            for j in 0..state.len() {
                let aux = state[j];
                state[j].square();
                state[j].square();
                state[j].mul_assign(&aux);
            }
        } else {
            let aux = state[0];
            state[0].square();
            state[0].square();
            state[0].mul_assign(&aux);
        }
    }

    pub fn mix(&self, state: &Vec<Fr>, m: &Vec<Vec<Fr>>) -> Vec<Fr> {
        let mut new_state: Vec<Fr> = Vec::new();
        for i in 0..state.len() {
            new_state.push(Fr::zero());
            for j in 0..state.len() {
                let mut mij = m[i][j];
                mij.mul_assign(&state[j]);
                new_state[i].add_assign(&mij);
            }
        }
        new_state.clone()
    }

    pub fn hash(&self, inp: Vec<Fr>) -> Result<Fr, String> {
        let t = inp.len() + 1;
        if inp.len() == 0 || inp.len() >= self.constants.n_rounds_p.len() - 1 {
            return Err("Wrong inputs length".to_string());
        }
        let n_rounds_f = self.constants.n_rounds_f.clone();
        let n_rounds_p = self.constants.n_rounds_p[t - 2].clone();

        let mut state = vec![Fr::zero(); t];
        state[1..].clone_from_slice(&inp);

        for i in 0..(n_rounds_f + n_rounds_p) {
            self.ark(&mut state, &self.constants.c[t - 2], i * t);
            self.sbox(n_rounds_f, n_rounds_p, &mut state, i);
            state = self.mix(&state, &self.constants.m[t - 2]);
        }

        Ok(state[0])
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_ff() {
        let a = Fr::from_repr(FrRepr::from(2)).unwrap();
        assert_eq!(
            "0000000000000000000000000000000000000000000000000000000000000002",
            to_hex(&a)
        );

        let b: Fr = Fr::from_str(
            "21888242871839275222246405745257275088548364400416034343698204186575808495619",
        )
        .unwrap();
        assert_eq!(
            "0000000000000000000000000000000000000000000000000000000000000002",
            to_hex(&b)
        );
        assert_eq!(&a, &b);
    }

    #[test]
    fn test_load_constants() {
        let cons = load_constants();
        assert_eq!(
            cons.c[0][0].to_string(),
            "Fr(0x09c46e9ec68e9bd4fe1faaba294cba38a71aa177534cdd1b6c7dc0dbd0abd7a7)"
        );
        assert_eq!(
            cons.c[cons.c.len() - 1][0].to_string(),
            "Fr(0x2088ce9534577bf38be7bc457f2756d558d66e0c07b9cc001a580bd42cda0e77)"
        );
        assert_eq!(
            cons.m[0][0][0].to_string(),
            "Fr(0x066f6f85d6f68a85ec10345351a23a3aaf07f38af8c952a7bceca70bd2af7ad5)"
        );
        assert_eq!(
            cons.m[cons.m.len() - 1][0][0].to_string(),
            "Fr(0x0190f922d97c8a7dcf0a142a3be27749d1c64bc22f1c556aaa24925d158cac56)"
        );
    }

    #[test]
    fn test_hash() {
        let b0: Fr = Fr::from_str("0").unwrap();
        let b1: Fr = Fr::from_str("1").unwrap();
        let b2: Fr = Fr::from_str("2").unwrap();
        let b3: Fr = Fr::from_str("3").unwrap();
        let b4: Fr = Fr::from_str("4").unwrap();
        let b5: Fr = Fr::from_str("5").unwrap();
        let b6: Fr = Fr::from_str("6").unwrap();

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b1.clone());
        let poseidon = Poseidon::new();
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x29176100eaa962bdc1fe6c654d6a3c130e96a4d1168b33848b897dc502820133)" // "18586133768512220936620570745912940619677854269274689475585506675881198879027"
        );

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b1.clone());
        big_arr.push(b2.clone());
        let poseidon = Poseidon::new();
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x115cc0f5e7d690413df64c6b9662e9cf2a3617f2743245519e19607a4417189a)" // "7853200120776062878684798364095072458815029376092732009249414926327459813530"
        );

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b1.clone());
        big_arr.push(b2.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        let poseidon = Poseidon::new();
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x024058dd1e168f34bac462b6fffe58fd69982807e9884c1c6148182319cee427)" // "1018317224307729531995786483840663576608797660851238720571059489595066344487"
        );

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b1.clone());
        big_arr.push(b2.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        let poseidon = Poseidon::new();
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x21e82f465e00a15965e97a44fe3c30f3bf5279d8bf37d4e65765b6c2550f42a1)" // "15336558801450556532856248569924170992202208561737609669134139141992924267169"
        );

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b3.clone());
        big_arr.push(b4.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        let poseidon = Poseidon::new();
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x0cd93f1bab9e8c9166ef00f2a1b0e1d66d6a4145e596abe0526247747cc71214)" // "5811595552068139067952687508729883632420015185677766880877743348592482390548"
        );

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b3.clone());
        big_arr.push(b4.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        big_arr.push(b0.clone());
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x1b1caddfc5ea47e09bb445a7447eb9694b8d1b75a97fff58e884398c6b22825a)" // "12263118664590987767234828103155242843640892839966517009184493198782366909018"
        );

        let mut big_arr: Vec<Fr> = Vec::new();
        big_arr.push(b1.clone());
        big_arr.push(b2.clone());
        big_arr.push(b3.clone());
        big_arr.push(b4.clone());
        big_arr.push(b5.clone());
        big_arr.push(b6.clone());
        let h = poseidon.hash(big_arr.clone()).unwrap();
        assert_eq!(
            h.to_string(),
            "Fr(0x2d1a03850084442813c8ebf094dea47538490a68b05f2239134a4cca2f6302e1)" // "20400040500897583745843009878988256314335038853985262692600694741116813247201"
        );
    }
}