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Optimize MiMC7 migrating from *big.Int to goff

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Optimize MiMC7 migrating from *big.Int to goff generated finite field
operations.

There is still a lot of room for optimization for MiMC7 in the way that is done internally, but will be done in the future.

Benchmarks:
Tested on a Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz, with 16GB of RAM.

- Before:
```
BenchmarkMIMC7-4   	    1026	   1160298 ns/op
```

- After this commit:
```
BenchmarkMIMC7-4   	   19263	     61651 ns/op
```
This commit is contained in:
arnaucube
2020-03-05 17:35:25 +01:00
parent e8be761ec7
commit 16a8a18a6d
3 changed files with 55 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files

95
mimc7/mimc7.go
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@@ -6,7 +6,7 @@ import (
"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/ff"
"github.com/iden3/go-iden3-crypto/utils"
)
@@ -15,73 +15,72 @@ const SEED = "mimc"
var constants = generateConstantsData()
type constantsData struct {
maxFieldVal *big.Int
seedHash *big.Int
iv *big.Int
fqR field.Fq
nRounds int
cts []*big.Int
seedHash *big.Int
iv *big.Int
nRounds int
cts []*ff.Element
}
func generateConstantsData() constantsData {
var constants constantsData
fqR := field.NewFq(_constants.Q)
constants.fqR = fqR
// maxFieldVal is the R value of the Finite Field
constants.maxFieldVal = constants.fqR.Q
constants.seedHash = new(big.Int).SetBytes(crypto.Keccak256([]byte(SEED)))
c := new(big.Int).SetBytes(crypto.Keccak256([]byte(SEED + "_iv")))
constants.iv = new(big.Int).Mod(c, constants.maxFieldVal)
constants.iv = new(big.Int).Mod(c, _constants.Q)
constants.nRounds = 91
cts := getConstants(constants.fqR, SEED, constants.nRounds)
cts := getConstants(SEED, constants.nRounds)
constants.cts = cts
return constants
}
func getConstants(fqR field.Fq, seed string, nRounds int) []*big.Int {
cts := make([]*big.Int, nRounds)
cts[0] = big.NewInt(int64(0))
func getConstants(seed string, nRounds int) []*ff.Element {
cts := make([]*ff.Element, nRounds)
cts[0] = ff.NewElement().SetZero()
c := new(big.Int).SetBytes(crypto.Keccak256([]byte(SEED)))
for i := 1; i < nRounds; i++ {
c = new(big.Int).SetBytes(crypto.Keccak256(c.Bytes()))
n := fqR.Affine(c)
cts[i] = n
n := new(big.Int).Mod(c, _constants.Q)
cts[i] = ff.NewElement().SetBigInt(n)
}
return cts
}
// 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
func MIMC7HashGeneric(xInBI, kBI *big.Int, nRounds int) *big.Int {
xIn := ff.NewElement().SetBigInt(xInBI)
k := ff.NewElement().SetBigInt(kBI)
cts := getConstants(SEED, nRounds)
var r *ff.Element
for i := 0; i < nRounds; i++ {
var t *big.Int
var t *ff.Element
if i == 0 {
t = fqR.Add(xIn, k)
t = ff.NewElement().Add(xIn, k)
} else {
t = fqR.Add(fqR.Add(r, k), cts[i])
t = ff.NewElement().Add(ff.NewElement().Add(r, k), cts[i])
}
t2 := fqR.Square(t)
t4 := fqR.Square(t2)
r = fqR.Mul(fqR.Mul(t4, t2), t)
t2 := ff.NewElement().Square(t)
t4 := ff.NewElement().Square(t2)
r = ff.NewElement().Mul(ff.NewElement().Mul(t4, t2), t)
}
return fqR.Affine(fqR.Add(r, k))
rE := ff.NewElement().Add(r, k)
res := big.NewInt(0)
rE.ToBigIntRegular(res)
return res
}
// 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) {
func HashGeneric(iv *big.Int, arr []*big.Int, nRounds int) (*big.Int, error) {
if !utils.CheckBigIntArrayInField(arr) {
return nil, errors.New("inputs values not inside Finite Field")
}
r := iv
var err error
for i := 0; i < len(arr); i++ {
r = MIMC7HashGeneric(fqR, r, arr[i], nRounds)
r = MIMC7HashGeneric(r, arr[i], nRounds)
if err != nil {
return r, err
}
@@ -90,20 +89,27 @@ func HashGeneric(iv *big.Int, arr []*big.Int, fqR field.Fq, nRounds int) (*big.I
}
// 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
func MIMC7Hash(xInBI, kBI *big.Int) *big.Int {
xIn := ff.NewElement().SetBigInt(xInBI)
k := ff.NewElement().SetBigInt(kBI)
var r *ff.Element
for i := 0; i < constants.nRounds; i++ {
var t *big.Int
var t *ff.Element
if i == 0 {
t = constants.fqR.Add(xIn, k)
t = ff.NewElement().Add(xIn, k)
} else {
t = constants.fqR.Add(constants.fqR.Add(r, k), constants.cts[i])
t = ff.NewElement().Add(ff.NewElement().Add(r, k), constants.cts[i])
}
t2 := constants.fqR.Square(t)
t4 := constants.fqR.Square(t2)
r = constants.fqR.Mul(constants.fqR.Mul(t4, t2), t)
t2 := ff.NewElement().Square(t)
t4 := ff.NewElement().Square(t2)
r = ff.NewElement().Mul(ff.NewElement().Mul(t4, t2), t)
}
return constants.fqR.Affine(constants.fqR.Add(r, k))
rE := ff.NewElement().Add(r, k)
res := big.NewInt(0)
rE.ToBigIntRegular(res)
return res
}
// Hash performs the MIMC7 hash over a *big.Int array
@@ -113,17 +119,18 @@ func Hash(arr []*big.Int, key *big.Int) (*big.Int, error) {
}
var r *big.Int
if key == nil {
r = constants.fqR.Zero()
r = big.NewInt(0)
} else {
r = key
}
for i := 0; i < len(arr); i++ {
r = constants.fqR.Add(
constants.fqR.Add(
r = new(big.Int).Add(
new(big.Int).Add(
r,
arr[i],
),
MIMC7Hash(arr[i], r))
r = new(big.Int).Mod(r, _constants.Q)
}
return r, nil
}