add mimc7

.gitignore

@@ -0,0 +1,3 @@
+/target
+**/*.rs.bk
+Cargo.lock

Cargo.toml

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+[package]
+name = "mimc-rs"
+version = "0.1.0"
+authors = ["arnaucube <root@arnaucube.com>"]
+edition = "2018"
+
+[dependencies]
+num = "0.2.0"
+num-bigint = "0.2.2"
+num-traits = "0.2.8"
+tiny-keccak = "1.5"
+rustc-hex = "1.0.0"

README.md

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+# mimc-rs
+MIMC7 hash implementation in Rust
+
+https://eprint.iacr.org/2016/492.pdf
+
+
+## Warning
+Do not use in production

src/lib.rs

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+extern crate num;
+extern crate num_bigint;
+extern crate num_traits;
+
+use tiny_keccak::Keccak;
+
+use num_bigint::{BigInt, Sign};
+use num_traits::Zero;
+
+const SEED: &str = "mimc";
+
+pub struct Constants {
+    seed_hash: BigInt,
+    iv: BigInt,
+    r: BigInt,
+    n_rounds: i64,
+    cts: Vec<BigInt>,
+}
+
+pub fn modulus(a: &BigInt, m: &BigInt) -> BigInt {
+    ((a % m) + m) % m
+}
+
+pub fn generate_constants() -> Constants {
+    let r: BigInt = BigInt::parse_bytes(
+        b"21888242871839275222246405745257275088548364400416034343698204186575808495617",
+        10,
+    )
+    .unwrap();
+
+    let mut keccak = Keccak::new_keccak256();
+    let mut h = [0u8; 32];
+    keccak.update(SEED.as_bytes());
+    keccak.finalize(&mut h);
+    let mut keccak = Keccak::new_keccak256();
+    let mut h_iv = [0u8; 32];
+    let seed_iv = format!("{}{}", SEED, "_iv");
+    keccak.update(seed_iv.as_bytes());
+    keccak.finalize(&mut h_iv);
+
+    let seed_hash: BigInt = BigInt::from_bytes_be(Sign::Plus, &h);
+    let c: BigInt = BigInt::from_bytes_be(Sign::Plus, &h_iv);
+    let iv: BigInt = c % &r;
+    let n_rounds: i64 = 91;
+    let cts = get_constants(&r, SEED, n_rounds);
+
+    Constants {
+        seed_hash: seed_hash,
+        iv: iv,
+        r: r,
+        n_rounds: n_rounds,
+        cts: cts,
+    }
+}
+
+pub fn get_constants(r: &BigInt, seed: &str, n_rounds: i64) -> Vec<BigInt> {
+    let mut cts: Vec<BigInt> = Vec::new();
+    cts.push(Zero::zero());
+
+    let mut keccak = Keccak::new_keccak256();
+    let mut h = [0u8; 32];
+    keccak.update(seed.as_bytes());
+    keccak.finalize(&mut h);
+
+    let mut c = BigInt::from_bytes_be(Sign::Plus, &h);
+    for _ in 1..n_rounds {
+        let mut keccak = Keccak::new_keccak256();
+        let mut h = [0u8; 32];
+        let (_, c_bytes) = c.to_bytes_be();
+        keccak.update(&c_bytes[..]);
+        keccak.finalize(&mut h);
+        c = BigInt::from_bytes_be(Sign::Plus, &h);
+        let n = modulus(&c, &r);
+        cts.push(n);
+    }
+    cts
+}
+
+pub fn mimc7_hash_generic(r: &BigInt, x_in: &BigInt, k: &BigInt, n_rounds: i64) -> BigInt {
+    let cts = get_constants(r, SEED, n_rounds);
+    let mut h: BigInt = Zero::zero();
+    for i in 0..n_rounds as usize {
+        let mut t: BigInt;
+        if i == 0 {
+            t = x_in + k;
+        } else {
+            t = h + k + &cts[i];
+        }
+        t = modulus(&t, &r);
+        let t2 = &t * &t;
+        let t4 = &t2 * &t2;
+        h = (t4 * t2) * t;
+        h = modulus(&h, &r);
+    }
+    modulus(&(h + k), &r)
+}
+
+pub fn hash_generic(iv: BigInt, arr: Vec<BigInt>, r: BigInt, n_rounds: i64) -> BigInt {
+    let mut h: BigInt = iv;
+    for i in 0..arr.len() {
+        h = mimc7_hash_generic(&r, &h, &arr[i], n_rounds);
+    }
+    h
+}
+
+pub struct Mimc7 {
+    constants: Constants,
+}
+
+impl Mimc7 {
+    pub fn new() -> Mimc7 {
+        Mimc7 {
+            constants: generate_constants(),
+        }
+    }
+
+    pub fn hash(&self, arr: Vec<BigInt>) -> BigInt {
+        // TODO check if arr elements are inside the Finite Field over R
+        let mut h: BigInt = Zero::zero();
+        for i in 0..arr.len() {
+            h = &h + &arr[i] + self.mimc7_hash(&arr[i], &h);
+            h = modulus(&h, &self.constants.r)
+        }
+        modulus(&h, &self.constants.r)
+    }
+
+    pub fn mimc7_hash(&self, x_in: &BigInt, k: &BigInt) -> BigInt {
+        let mut h: BigInt = Zero::zero();
+        for i in 0..self.constants.n_rounds as usize {
+            let t: BigInt;
+            if i == 0 {
+                t = x_in + k;
+            } else {
+                t = h + k + &self.constants.cts[i];
+            }
+            let t2 = &t * &t;
+            let t4 = &t2 * &t2;
+            h = (t4 * t2) * t;
+            h = modulus(&h, &self.constants.r);
+        }
+        modulus(&(h + k), &self.constants.r)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use rustc_hex::ToHex;
+
+    #[test]
+    fn test_sha3() {
+        let mut keccak = Keccak::new_keccak256();
+        let mut res = [0u8; 32];
+        keccak.update(SEED.as_bytes());
+        keccak.finalize(&mut res);
+        assert_eq!(
+            res.to_hex(),
+            "b6e489e6b37224a50bebfddbe7d89fa8fdcaa84304a70bd13f79b5d9f7951e9e"
+        );
+
+        let mut keccak = Keccak::new_keccak256();
+        let mut res = [0u8; 32];
+        keccak.update(SEED.as_bytes());
+        keccak.finalize(&mut res);
+        let c = BigInt::from_bytes_be(Sign::Plus, &res);
+        assert_eq!(
+            c.to_string(),
+            "82724731331859054037315113496710413141112897654334566532528783843265082629790"
+        );
+    }
+    #[test]
+    fn test_generate_constants() {
+        let constants = generate_constants();
+        assert_eq!(
+            "20888961410941983456478427210666206549300505294776164667214940546594746570981",
+            constants.cts[1].to_string()
+        );
+    }
+
+    #[test]
+    fn test_mimc7_generic() {
+        let b1: BigInt = BigInt::parse_bytes(b"1", 10).unwrap();
+        let b2: BigInt = BigInt::parse_bytes(b"2", 10).unwrap();
+        let constants = generate_constants();
+        let h1 = mimc7_hash_generic(&constants.r, &b1, &b2, 91);
+        assert_eq!(
+            h1.to_string(),
+            "10594780656576967754230020536574539122676596303354946869887184401991294982664"
+        );
+    }
+    #[test]
+    fn test_mimc7() {
+        let b12: BigInt = BigInt::parse_bytes(b"12", 10).unwrap();
+        let b45: BigInt = BigInt::parse_bytes(b"45", 10).unwrap();
+        let b78: BigInt = BigInt::parse_bytes(b"78", 10).unwrap();
+        let b41: BigInt = BigInt::parse_bytes(b"41", 10).unwrap();
+
+        let mut big_arr1: Vec<BigInt> = Vec::new();
+        big_arr1.push(b12.clone());
+        let mimc7 = Mimc7::new();
+        let h1 = mimc7.hash(big_arr1);
+        let (_, h1_bytes) = h1.to_bytes_be();
+        assert_eq!(
+            h1_bytes.to_hex(),
+            "237c92644dbddb86d8a259e0e923aaab65a93f1ec5758b8799988894ac0958fd"
+        );
+
+        let mh2 = mimc7.mimc7_hash(&b12, &b45);
+        let (_, mh2_bytes) = mh2.to_bytes_be();
+        assert_eq!(
+            mh2_bytes.to_hex(),
+            "2ba7ebad3c6b6f5a20bdecba2333c63173ca1a5f2f49d958081d9fa7179c44e4"
+        );
+
+        let mut big_arr2: Vec<BigInt> = Vec::new();
+        big_arr2.push(b78.clone());
+        big_arr2.push(b41.clone());
+        let h2 = mimc7.hash(big_arr2);
+        let (_, h2_bytes) = h2.to_bytes_be();
+        assert_eq!(
+            h2_bytes.to_hex(),
+            "067f3202335ea256ae6e6aadcd2d5f7f4b06a00b2d1e0de903980d5ab552dc70"
+        );
+
+        let mut big_arr2: Vec<BigInt> = Vec::new();
+        big_arr2.push(b12.clone());
+        big_arr2.push(b45.clone());
+        let h1 = mimc7.hash(big_arr2);
+        let (_, h1_bytes) = h1.to_bytes_be();
+        assert_eq!(
+            h1_bytes.to_hex(),
+            "15ff7fe9793346a17c3150804bcb36d161c8662b110c50f55ccb7113948d8879"
+        );
+
+        let mut big_arr1: Vec<BigInt> = Vec::new();
+        big_arr1.push(b12.clone());
+        big_arr1.push(b45.clone());
+        big_arr1.push(b78.clone());
+        big_arr1.push(b41.clone());
+        let mimc7 = Mimc7::new();
+        let h1 = mimc7.hash(big_arr1);
+        let (_, h1_bytes) = h1.to_bytes_be();
+        assert_eq!(
+            h1_bytes.to_hex(),
+            "284bc1f34f335933a23a433b6ff3ee179d682cd5e5e2fcdd2d964afa85104beb"
+        );
+    }
+}