From 58f758d5ada9672a5ca5282c88f051e25a4f0b09 Mon Sep 17 00:00:00 2001
From: Jordi Baylina <jordi@baylina.cat>
Date: Sun, 28 Apr 2019 12:03:15 +0100
Subject: [PATCH] Adapt the way to connect mimcs

---
 circuits/eddsamimc.circom   |  1 +
 circuits/mimc.circom        | 15 ++++++++-------
 circuits/smt/smthash.circom | 30 ++++++++++--------------------
 src/eddsa.js                |  2 +-
 src/mimc7.js                | 19 +++++++++++++++----
 src/smt.js                  | 32 ++++++++++++++++----------------
 test/eddsamimc.js           |  2 +-
 7 files changed, 52 insertions(+), 49 deletions(-)

diff --git a/circuits/eddsamimc.circom b/circuits/eddsamimc.circom
index 3bc870e..b3a6a77 100644
--- a/circuits/eddsamimc.circom
+++ b/circuits/eddsamimc.circom
@@ -58,6 +58,7 @@ template EdDSAMiMCVerifier() {
     hash.in[2] <== Ax;
     hash.in[3] <== Ay;
     hash.in[4] <== M;
+    hash.k <== 0;
 
     component h2bits = Num2Bits_strict();
     h2bits.in <== hash.out;
diff --git a/circuits/mimc.circom b/circuits/mimc.circom
index ea2c274..9ab478e 100644
--- a/circuits/mimc.circom
+++ b/circuits/mimc.circom
@@ -137,18 +137,19 @@ template MiMC7(nrounds) {
 
 template MultiMiMC7(nInputs, nRounds) {
     signal input in[nInputs];
+    signal input k;
     signal output out;
+    signal r[nInputs +1];
 
     component mims[nInputs];
+
+    r[0] <== k;
     for (var i=0; i<nInputs; i++) {
         mims[i] = MiMC7(nRounds);
-        if (i==0) {
-            mims[i].x_in <== 15021630795539610737508582392395901278341266317943626182700664337106830745361;
-        } else {
-            mims[i].x_in <== mims[i-1].out;
-        }
-        mims[i].k <== in[i];
+        mims[i].x_in <== in[i];
+        mims[i].k <== r[i];
+        r[i+1] <== r[i] + in[i] + mims[i].out;
     }
 
-    out <== mims[nInputs-1].out;
+    out <== r[nInputs];
 }
diff --git a/circuits/smt/smthash.circom b/circuits/smt/smthash.circom
index baba85e..bad5290 100644
--- a/circuits/smt/smthash.circom
+++ b/circuits/smt/smthash.circom
@@ -29,19 +29,12 @@ template SMTHash1() {
     signal input value;
     signal output out;
 
-    component h1 = MiMC7(91);   // Constant
-    h1.x_in <== 15021630795539610737508582392395901278341266317943626182700664337106830745361;
-    h1.k <== 1;
+    component h = MultiMiMC7(2, 91);   // Constant
+    h.in[0] <== key;
+    h.in[1] <== value;
+    h.k <== 1;
 
-    component h2 = MiMC7(91);
-    h2.x_in <== h1.out;
-    h2.k <== key;
-
-    component h3 = MiMC7(91);
-    h3.x_in <== h2.out;
-    h3.k <== value;
-
-    out <== h3.out;
+    out <== h.out;
 }
 
 /*
@@ -55,13 +48,10 @@ template SMTHash2() {
     signal input R;
     signal output out;
 
-    component h1 = MiMC7(91);
-    h1.x_in <== 15021630795539610737508582392395901278341266317943626182700664337106830745361;
-    h1.k <== L;
-
-    component h2 = MiMC7(91);
-    h2.x_in <== h1.out;
-    h2.k <== R;
+    component h = MultiMiMC7(2, 91);   // Constant
+    h.in[0] <== L;
+    h.in[1] <== R;
+    h.k <== 0;
 
-    out <== h2.out;
+    out <== h.out;
 }
diff --git a/src/eddsa.js b/src/eddsa.js
index 4991881..f3079f3 100644
--- a/src/eddsa.js
+++ b/src/eddsa.js
@@ -3,7 +3,7 @@ const bigInt = require("snarkjs").bigInt;
 const babyJub = require("./babyjub");
 const pedersenHash = require("./pedersenHash").hash;
 const mimc7 = require("./mimc7");
-    
+
 exports.prv2pub= prv2pub;
 exports.sign = sign;
 exports.signMiMC = signMiMC;
diff --git a/src/mimc7.js b/src/mimc7.js
index 47291d8..d2f84c1 100644
--- a/src/mimc7.js
+++ b/src/mimc7.js
@@ -44,10 +44,21 @@ exports.hash =  (_x_in, _k) =>{
     return F.affine(F.add(r, k));
 };
 
-exports.multiHash = (arr) => {
-    let r = exports.getIV();
+exports.multiHash = (arr, key) => {
+    let r;
+    if (typeof(key) === "undefined") {
+        r = F.zero;
+    } else {
+        r = key;
+    }
     for (let i=0; i<arr.length; i++) {
-        r = exports.hash(r, bigInt(arr[i]));
+        r = F.add(
+            F.add(
+                r,
+                arr[i]
+            ),
+            exports.hash(bigInt(arr[i]), r)
+        );
     }
-    return r;
+    return F.affine(r);
 };
diff --git a/src/smt.js b/src/smt.js
index 2486307..5b4521e 100644
--- a/src/smt.js
+++ b/src/smt.js
@@ -46,8 +46,8 @@ class SMT {
         const ins = [];
         const dels = [];
 
-        let rtOld = mimc7.multiHash([1, key, resFind.foundValue]);
-        let rtNew = mimc7.multiHash([1, key, newValue]);
+        let rtOld = mimc7.multiHash([key, resFind.foundValue], bigInt.one);
+        let rtNew = mimc7.multiHash([key, newValue], bigInt.one);
         ins.push([rtNew, [1, key, newValue ]]);
         dels.push(rtOld);
 
@@ -59,11 +59,11 @@ class SMT {
                 oldNode = [sibling, rtOld];
                 newNode = [sibling, rtNew];
             } else {
-                oldNode = [rtOld, sibling, ];
-                newNode = [rtNew, sibling, ];
+                oldNode = [rtOld, sibling];
+                newNode = [rtNew, sibling];
             }
-            rtOld = mimc7.multiHash(oldNode);
-            rtNew = mimc7.multiHash(newNode);
+            rtOld = mimc7.multiHash(oldNode, bigInt.zero);
+            rtNew = mimc7.multiHash(newNode, bigInt.zero);
             dels.push(rtOld);
             ins.push([rtNew, newNode]);
         }
@@ -92,7 +92,7 @@ class SMT {
 
         const dels = [];
         const ins = [];
-        let rtOld = mimc7.multiHash([1, key, resFind.foundValue]);
+        let rtOld = mimc7.multiHash([key, resFind.foundValue], bigInt.one);
         let rtNew;
         dels.push(rtOld);
 
@@ -130,9 +130,9 @@ class SMT {
             }
             const oldSibling = resFind.siblings[level];
             if (keyBits[level]) {
-                rtOld = mimc7.multiHash([oldSibling, rtOld]);
+                rtOld = mimc7.multiHash([oldSibling, rtOld], bigInt.zero);
             } else {
-                rtOld = mimc7.multiHash([rtOld, oldSibling]);
+                rtOld = mimc7.multiHash([rtOld, oldSibling], bigInt.zero);
             }
             dels.push(rtOld);
             if (!newSibling.isZero()) {
@@ -147,7 +147,7 @@ class SMT {
                 } else {
                     newNode = [rtNew, newSibling];
                 }
-                rtNew = mimc7.multiHash(newNode);
+                rtNew = mimc7.multiHash(newNode, bigInt.zero);
                 ins.push([rtNew, newNode]);
             }
         }
@@ -185,7 +185,7 @@ class SMT {
             for (let i= res.siblings.length; oldKeyits[i] == newKeyBits[i]; i++) {
                 res.siblings.push(bigInt.zero);
             }
-            rtOld = mimc7.multiHash([1, resFind.notFoundKey, resFind.notFoundValue]);
+            rtOld = mimc7.multiHash([resFind.notFoundKey, resFind.notFoundValue], bigInt.one);
             res.siblings.push(rtOld);
             addedOne = true;
             mixed = false;
@@ -197,7 +197,7 @@ class SMT {
         const inserts = [];
         const dels = [];
 
-        let rt = mimc7.multiHash([1, key, value]);
+        let rt = mimc7.multiHash([key, value], bigInt.one);
         inserts.push([rt,[1, key, value]] );
 
         for (let i=res.siblings.length-1; i>=0; i--) {
@@ -207,9 +207,9 @@ class SMT {
             if (mixed) {
                 const oldSibling = resFind.siblings[i];
                 if (newKeyBits[i]) {
-                    rtOld = mimc7.multiHash([oldSibling, rtOld]);
+                    rtOld = mimc7.multiHash([oldSibling, rtOld], bigInt.zero);
                 } else {
-                    rtOld = mimc7.multiHash([rtOld, oldSibling]);
+                    rtOld = mimc7.multiHash([rtOld, oldSibling], bigInt.zero);
                 }
                 dels.push(rtOld);
             }
@@ -217,10 +217,10 @@ class SMT {
 
             let newRt;
             if (newKeyBits[i]) {
-                newRt = mimc7.multiHash([res.siblings[i], rt]);
+                newRt = mimc7.multiHash([res.siblings[i], rt], bigInt.zero);
                 inserts.push([newRt,[res.siblings[i], rt]] );
             } else {
-                newRt = mimc7.multiHash([rt, res.siblings[i]]);
+                newRt = mimc7.multiHash([rt, res.siblings[i]],  bigInt.zero);
                 inserts.push([newRt,[rt, res.siblings[i]]] );
             }
             rt = newRt;
diff --git a/test/eddsamimc.js b/test/eddsamimc.js
index 9aec29a..97abcb3 100644
--- a/test/eddsamimc.js
+++ b/test/eddsamimc.js
@@ -9,7 +9,7 @@ const assert = chai.assert;
 
 const bigInt = snarkjs.bigInt;
 
-describe("EdDSA test", function () {
+describe("EdDSA MiMC test", function () {
     let circuit;
 
     this.timeout(100000);