MiMC7 finite field over R comprovation moved inside hash, same approach as Poseidon impl

babyjub/eddsa.go

@@ -180,11 +180,11 @@ func (k *PrivateKey) SignMimc7(msg *big.Int) *Signature {
 	r.Mod(r, SubOrder)
 	R8 := NewPoint().Mul(r, B8) // R8 = r * 8 * B
 	A := k.Public().Point()
-	hmInput, err := mimc7.BigIntsToRElems([]*big.Int{R8.X, R8.Y, A.X, A.Y, msg})
+	hmInput := []*big.Int{R8.X, R8.Y, A.X, A.Y, msg}
+	hm, err := mimc7.Hash(hmInput, nil) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 	if err != nil {
 		panic(err)
 	}
-	hm := mimc7.Hash(hmInput, nil) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 	S := new(big.Int).Lsh(k.Scalar().BigInt(), 3)
 	S = S.Mul(hm, S)
 	S.Add(r, S)
@@ -196,11 +196,11 @@ func (k *PrivateKey) SignMimc7(msg *big.Int) *Signature {
 // VerifyMimc7 verifies the signature of a message encoded as a big.Int in Zq
 // using blake-512 hash for buffer hashing and mimc7 for big.Int hashing.
 func (p *PublicKey) VerifyMimc7(msg *big.Int, sig *Signature) bool {
-	hmInput, err := mimc7.BigIntsToRElems([]*big.Int{sig.R8.X, sig.R8.Y, p.X, p.Y, msg})
+	hmInput := []*big.Int{sig.R8.X, sig.R8.Y, p.X, p.Y, msg}
+	hm, err := mimc7.Hash(hmInput, nil) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 	if err != nil {
 		panic(err)
 	}
-	hm := mimc7.Hash(hmInput, nil) // hm = H1(8*R.x, 8*R.y, A.x, A.y, msg)
 
 	left := NewPoint().Mul(sig.S, B8) // left = s * 8 * B
 	r1 := big.NewInt(8)

mimc7/mimc7.go

@@ -2,19 +2,16 @@ package mimc7
 
 import (
 	"errors"
-	"fmt"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/crypto"
 	_constants "github.com/iden3/go-iden3-crypto/constants"
 	"github.com/iden3/go-iden3-crypto/field"
+	"github.com/iden3/go-iden3-crypto/utils"
 )
 
 const SEED = "mimc"
 
-// RElem is a big.Int of maximum 253 bits
-type RElem *big.Int
-
 var constants = generateConstantsData()
 
 type constantsData struct {
@@ -45,36 +42,6 @@ func generateConstantsData() constantsData {
 	return constants
 }
 
-// BigIntToRElem checks if given big.Int fits in a Field R element, and returns the RElem type
-func BigIntToRElem(a *big.Int) (RElem, error) {
-	if a.Cmp(constants.maxFieldVal) != -1 {
-		return RElem(a), errors.New("Given big.Int don't fits in the Finite Field over R")
-	}
-	return RElem(a), nil
-}
-
-//BigIntsToRElems converts from array of *big.Int to array of RElem
-func BigIntsToRElems(arr []*big.Int) ([]RElem, error) {
-	o := make([]RElem, len(arr))
-	for i, a := range arr {
-		e, err := BigIntToRElem(a)
-		if err != nil {
-			return o, fmt.Errorf("element in position %v don't fits in Finite Field over R", i)
-		}
-		o[i] = e
-	}
-	return o, nil
-}
-
-// RElemsToBigInts converts from array of RElem to array of *big.Int
-func RElemsToBigInts(arr []RElem) []*big.Int {
-	o := make([]*big.Int, len(arr))
-	for i, a := range arr {
-		o[i] = a
-	}
-	return o
-}
-
 func getConstants(fqR field.Fq, seed string, nRounds int) []*big.Int {
 	cts := make([]*big.Int, nRounds)
 	cts[0] = big.NewInt(int64(0))
@@ -88,7 +55,7 @@ func getConstants(fqR field.Fq, seed string, nRounds int) []*big.Int {
 	return cts
 }
 
-// MIMC7HashGeneric performs the MIMC7 hash over a RElem, in a generic way, where it can be specified the Finite Field over R, and the number of rounds
+// MIMC7HashGeneric performs the MIMC7 hash over a *big.Int, in a generic way, where it can be specified the Finite Field over R, and the number of rounds
 func MIMC7HashGeneric(fqR field.Fq, xIn, k *big.Int, nRounds int) *big.Int {
 	cts := getConstants(fqR, SEED, nRounds)
 	var r *big.Int
@@ -106,9 +73,11 @@ func MIMC7HashGeneric(fqR field.Fq, xIn, k *big.Int, nRounds int) *big.Int {
 	return fqR.Affine(fqR.Add(r, k))
 }
 
-// HashGeneric performs the MIMC7 hash over a RElem array, in a generic way, where it can be specified the Finite Field over R, and the number of rounds
-func HashGeneric(iv *big.Int, arrEl []RElem, fqR field.Fq, nRounds int) (RElem, error) {
-	arr := RElemsToBigInts(arrEl)
+// HashGeneric performs the MIMC7 hash over a *big.Int array, in a generic way, where it can be specified the Finite Field over R, and the number of rounds
+func HashGeneric(iv *big.Int, arr []*big.Int, fqR field.Fq, nRounds int) (*big.Int, error) {
+	if !utils.CheckBigIntArrayInField(arr, constants.fqR.Q) {
+		return nil, errors.New("inputs values not inside Finite Field")
+	}
 	r := iv
 	var err error
 	for i := 0; i < len(arr); i++ {
@@ -117,10 +86,10 @@ func HashGeneric(iv *big.Int, arrEl []RElem, fqR field.Fq, nRounds int) (RElem,
 			return r, err
 		}
 	}
-	return RElem(r), nil
+	return r, nil
 }
 
-// MIMC7Hash performs the MIMC7 hash over a RElem, using the Finite Field over R and the number of rounds setted in the `constants` variable
+// MIMC7Hash performs the MIMC7 hash over a *big.Int, using the Finite Field over R and the number of rounds setted in the `constants` variable
 func MIMC7Hash(xIn, k *big.Int) *big.Int {
 	var r *big.Int
 	for i := 0; i < constants.nRounds; i++ {
@@ -137,16 +106,17 @@ func MIMC7Hash(xIn, k *big.Int) *big.Int {
 	return constants.fqR.Affine(constants.fqR.Add(r, k))
 }
 
-// Hash performs the MIMC7 hash over a RElem array
-func Hash(arrEl []RElem, key *big.Int) RElem {
-	arr := RElemsToBigInts(arrEl)
+// Hash performs the MIMC7 hash over a *big.Int array
+func Hash(arr []*big.Int, key *big.Int) (*big.Int, error) {
+	if !utils.CheckBigIntArrayInField(arr, constants.fqR.Q) {
+		return nil, errors.New("inputs values not inside Finite Field")
+	}
 	var r *big.Int
 	if key == nil {
 		r = constants.fqR.Zero()
 	} else {
 		r = key
 	}
-	// r := constants.iv
 	for i := 0; i < len(arr); i++ {
 		r = constants.fqR.Add(
 			constants.fqR.Add(
@@ -155,5 +125,5 @@ func Hash(arrEl []RElem, key *big.Int) RElem {
 			),
 			MIMC7Hash(arr[i], r))
 	}
-	return RElem(r)
+	return r, nil
 }

mimc7/mimc7_test.go

@@ -10,40 +10,6 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
-func TestUtils(t *testing.T) {
-	b1 := big.NewInt(int64(1))
-	b2 := big.NewInt(int64(2))
-	b3 := big.NewInt(int64(3))
-	arrBigInt := []*big.Int{b1, b2, b3}
-
-	// *big.Int array to RElem array
-	rElems, err := BigIntsToRElems(arrBigInt)
-	assert.Nil(t, err)
-
-	// RElem array to *big.Int array
-	bElems := RElemsToBigInts(rElems)
-
-	assert.Equal(t, arrBigInt, bElems)
-
-	r, ok := new(big.Int).SetString("21888242871839275222246405745257275088548364400416034343698204186575808495617", 10)
-	assert.True(t, ok)
-
-	// greater or equal than R will give error when passing bigInts to RElems, to fit in the R Finite Field
-	overR, ok := new(big.Int).SetString("21888242871839275222246405745257275088548364400416034343698204186575808495618", 10)
-	assert.True(t, ok)
-	_, err = BigIntsToRElems([]*big.Int{b1, overR, b2})
-	assert.True(t, err != nil)
-
-	_, err = BigIntsToRElems([]*big.Int{b1, r, b2})
-	assert.True(t, err != nil)
-
-	// smaller than R will not give error when passing bigInts to RElems, to fit in the R Finite Field
-	underR, ok := new(big.Int).SetString("21888242871839275222246405745257275088548364400416034343698204186575808495616", 10)
-	assert.True(t, ok)
-	_, err = BigIntsToRElems([]*big.Int{b1, underR, b2})
-	assert.Nil(t, err)
-}
-
 func TestKeccak256(t *testing.T) {
 	res := crypto.Keccak256([]byte(SEED))
 	assert.Equal(t, "b6e489e6b37224a50bebfddbe7d89fa8fdcaa84304a70bd13f79b5d9f7951e9e", hex.EncodeToString(res))
@@ -61,14 +27,11 @@ func TestMIMC7Generic(t *testing.T) {
 	fqR := field.NewFq(r)
 
 	bigArray := []*big.Int{b1, b2, b3}
-	elementsArray, err := BigIntsToRElems(bigArray)
-	assert.Nil(t, err)
 
 	// Generic Hash
 	mhg := MIMC7HashGeneric(fqR, b1, b2, 91)
-	assert.Nil(t, err)
 	assert.Equal(t, "10594780656576967754230020536574539122676596303354946869887184401991294982664", mhg.String())
-	hg, err := HashGeneric(fqR.Zero(), elementsArray, fqR, 91)
+	hg, err := HashGeneric(fqR.Zero(), bigArray, fqR, 91)
 	assert.Nil(t, err)
 	assert.Equal(t, "6464402164086696096195815557694604139393321133243036833927490113253119343397", (*big.Int)(hg).String())
 }
@@ -81,44 +44,36 @@ func TestMIMC7(t *testing.T) {
 
 	// h1, hash of 1 elements
 	bigArray1 := []*big.Int{b12}
-	elementsArray1, err := BigIntsToRElems(bigArray1)
-	assert.Nil(t, err)
 
-	h1 := Hash(elementsArray1, nil)
+	h1, err := Hash(bigArray1, nil)
 	assert.Nil(t, err)
 	// same hash value than the iden3js and circomlib tests:
 	assert.Equal(t, "0x"+hex.EncodeToString((*big.Int)(h1).Bytes()), "0x237c92644dbddb86d8a259e0e923aaab65a93f1ec5758b8799988894ac0958fd")
 
 	// h2a, hash of 2 elements
 	bigArray2a := []*big.Int{b78, b41}
-	elementsArray2a, err := BigIntsToRElems(bigArray2a)
-	assert.Nil(t, err)
 
-	h2a := Hash(elementsArray2a, nil)
+	h2a, err := Hash(bigArray2a, nil)
 	assert.Nil(t, err)
 	// same hash value than the iden3js and circomlib tests:
 	assert.Equal(t, "0x"+hex.EncodeToString((*big.Int)(h2a).Bytes()), "0x067f3202335ea256ae6e6aadcd2d5f7f4b06a00b2d1e0de903980d5ab552dc70")
 
 	// h2b, hash of 2 elements
 	bigArray2b := []*big.Int{b12, b45}
-	elementsArray2b, err := BigIntsToRElems(bigArray2b)
-	assert.Nil(t, err)
 
 	mh2b := MIMC7Hash(b12, b45)
 	assert.Nil(t, err)
 	assert.Equal(t, "0x"+hex.EncodeToString((*big.Int)(mh2b).Bytes()), "0x2ba7ebad3c6b6f5a20bdecba2333c63173ca1a5f2f49d958081d9fa7179c44e4")
 
-	h2b := Hash(elementsArray2b, nil)
+	h2b, err := Hash(bigArray2b, nil)
 	assert.Nil(t, err)
 	// same hash value than the iden3js and circomlib tests:
 	assert.Equal(t, "0x"+hex.EncodeToString((*big.Int)(h2b).Bytes()), "0x15ff7fe9793346a17c3150804bcb36d161c8662b110c50f55ccb7113948d8879")
 
 	// h4, hash of 4 elements
 	bigArray4 := []*big.Int{b12, b45, b78, b41}
-	elementsArray4, err := BigIntsToRElems(bigArray4)
-	assert.Nil(t, err)
 
-	h4 := Hash(elementsArray4, nil)
+	h4, err := Hash(bigArray4, nil)
 	assert.Nil(t, err)
 	// same hash value than the iden3js and circomlib tests:
 	assert.Equal(t, "0x"+hex.EncodeToString((*big.Int)(h4).Bytes()), "0x284bc1f34f335933a23a433b6ff3ee179d682cd5e5e2fcdd2d964afa85104beb")
@@ -130,12 +85,10 @@ func BenchmarkMIMC7(b *testing.B) {
 	b78 := big.NewInt(int64(78))
 	b41 := big.NewInt(int64(41))
 	bigArray4 := []*big.Int{b12, b45, b78, b41}
-	elementsArray4, err := BigIntsToRElems(bigArray4)
-	assert.Nil(b, err)
 
-	var h4 RElem
+	var h4 *big.Int
 	for i := 0; i < b.N; i++ {
-		h4 = Hash(elementsArray4, nil)
+		h4, _ = Hash(bigArray4, nil)
 	}
 	println(h4)
 }