Merge other basic circuits here

src/mimc7.js

@@ -0,0 +1,37 @@
+const bn128 = require("snarkjs").bn128;
+const bigInt = require("snarkjs").bigInt;
+const Web3 = require("web3");
+const F = bn128.Fr;
+
+module.exports.hash = MiMC7Hash;
+module.exports.getConstants = getConstants;
+
+const SEED = "iden3_mimc";
+
+function getConstants(seed, nRounds) {
+    const cts = new Array(nRounds);
+    let c = Web3.utils.keccak256(SEED);
+    for (let i=1; i<nRounds; i++) {
+        c = Web3.utils.keccak256(c);
+
+        const n1 = Web3.utils.toBN(c).mod(Web3.utils.toBN(F.q.toString()));
+        cts[i] = Web3.utils.padLeft(Web3.utils.toHex(n1), 64);
+    }
+    cts[0] = "0x0000000000000000000000000000000000000000000000000000000000000000";
+    return cts;
+}
+
+function MiMC7Hash(_x_in, _k, nRounds) {
+    const x_in = bigInt(_x_in);
+    const k = bigInt(_k);
+    const cts = getConstants(SEED, nRounds);
+    let r;
+    for (let i=0; i<nRounds; i++) {
+        const c = bigInt(Web3.utils.toBN(cts[i]).toString());
+        let t = (i==0) ? F.add(x_in, k) : F.add(F.add(r, k), c);
+        let t2 = F.square(t);
+        let t4 = F.square(t2);
+        r = F.mul(F.mul(t4, t2), t);
+    }
+    return F.affine(F.add(r, k));
+}