Merge pull request #1258 from Consensys/refactor/limb-composition

refactor: utility methods into separate internal package for reuse in std library

constraint/gkr.go

@@ -2,10 +2,11 @@ package constraint
 
 import (
  "fmt"
+ "sort"
+
  "github.com/consensys/gnark-crypto/utils"
  "github.com/consensys/gnark/constraint/solver"
- "github.com/consensys/gnark/std/utils/algo_utils"
- "sort"
+ "github.com/consensys/gnark/internal/algo_utils"
 )
 
 type GkrVariable int // Just an alias to hide implementation details. May be more trouble than worth

internal/generator/backend/template/representations/gkr.go.tmpl

@@ -7,7 +7,7 @@ import (
  "github.com/consensys/gnark-crypto/utils"
  "github.com/consensys/gnark/constraint"
  hint "github.com/consensys/gnark/constraint/solver"
- "github.com/consensys/gnark/std/utils/algo_utils"
+ "github.com/consensys/gnark/internal/algo_utils"
  "hash"
  "math/big"
  "sync"

std/compress/internal/io_test.go

@@ -3,19 +3,20 @@ package internal_test
 import (
  "bytes"
  "crypto/rand"
+ "testing"
+
  "github.com/consensys/gnark-crypto/ecc"
  "github.com/consensys/gnark/backend"
  "github.com/consensys/gnark/frontend"
  "github.com/consensys/gnark/frontend/cs/scs"
  "github.com/consensys/gnark/std/compress"
  "github.com/consensys/gnark/std/compress/internal"
  "github.com/consensys/gnark/std/compress/lzss"
+ test_vector_utils "github.com/consensys/gnark/std/internal/test_vectors_utils"
  "github.com/consensys/gnark/std/math/bits"
- test_vector_utils "github.com/consensys/gnark/std/utils/test_vectors_utils"
  "github.com/consensys/gnark/test"
  "github.com/icza/bitio"
  "github.com/stretchr/testify/assert"
- "testing"
 )
 
 func TestRecombineBytes(t *testing.T) {

std/compress/internal/plonk/plonk_test.go

@@ -4,14 +4,15 @@ import (
  "crypto/rand"
  "encoding/binary"
  "errors"
+ "reflect"
+ "testing"
+
  "github.com/consensys/gnark-crypto/ecc"
  "github.com/consensys/gnark-crypto/ecc/bls12-377/fr"
  "github.com/consensys/gnark/backend"
  "github.com/consensys/gnark/frontend"
- test_vector_utils "github.com/consensys/gnark/std/utils/test_vectors_utils"
+ test_vector_utils "github.com/consensys/gnark/std/internal/test_vectors_utils"
  "github.com/consensys/gnark/test"
- "reflect"
- "testing"
 )
 
 func TestCustomConstraint(t *testing.T) {

std/compress/io_test.go

@@ -4,18 +4,19 @@ import (
  "crypto/rand"
  "errors"
  "fmt"
+ "math/big"
+ "testing"
+
  "github.com/consensys/gnark-crypto/ecc"
  "github.com/consensys/gnark-crypto/ecc/bls12-377/fr"
  "github.com/consensys/gnark-crypto/hash"
  "github.com/consensys/gnark/backend"
  "github.com/consensys/gnark/frontend"
  "github.com/consensys/gnark/frontend/cs/scs"
  "github.com/consensys/gnark/profile"
- test_vector_utils "github.com/consensys/gnark/std/utils/test_vectors_utils"
+ test_vector_utils "github.com/consensys/gnark/std/internal/test_vectors_utils"
  "github.com/consensys/gnark/test"
  "github.com/stretchr/testify/assert"
- "math/big"
- "testing"
 )
 
 func TestShiftLeft(t *testing.T) {

std/compress/lzss/snark_test.go

@@ -4,15 +4,16 @@ import (
  "crypto/sha256"
  "encoding/hex"
  "fmt"
- "github.com/consensys/gnark/frontend/cs/scs"
  "os"
  "testing"
 
+ "github.com/consensys/gnark/frontend/cs/scs"
+
  "github.com/consensys/compress/lzss"
  "github.com/consensys/gnark-crypto/ecc"
  "github.com/consensys/gnark/backend"
  "github.com/consensys/gnark/frontend"
- test_vector_utils "github.com/consensys/gnark/std/utils/test_vectors_utils"
+ test_vector_utils "github.com/consensys/gnark/std/internal/test_vectors_utils"
  "github.com/consensys/gnark/test"
  "github.com/stretchr/testify/assert"
  "github.com/stretchr/testify/require"

std/compress/lzss/snark_testing.go

@@ -4,7 +4,7 @@ import (
  "github.com/consensys/compress/lzss"
  "github.com/consensys/gnark/frontend"
  "github.com/consensys/gnark/std/compress"
- test_vector_utils "github.com/consensys/gnark/std/utils/test_vectors_utils"
+ test_vector_utils "github.com/consensys/gnark/std/internal/test_vectors_utils"
 )
 
 type DecompressionTestCircuit struct {

std/evmprecompiles/hints.go

@@ -8,6 +8,7 @@ import (
  "github.com/consensys/gnark-crypto/ecc/secp256k1/ecdsa"
  "github.com/consensys/gnark/constraint/solver"
  "github.com/consensys/gnark/frontend"
+ limbs "github.com/consensys/gnark/std/internal/limbcomposition"
  "github.com/consensys/gnark/std/math/emulated"
 )
 
@@ -46,10 +47,20 @@ func recoverPublicKeyHint(_ *big.Int, inputs []*big.Int, outputs []*big.Int) err
  if len(outputs) != 2*int(emfp.NbLimbs())+1 {
  return fmt.Errorf("expected output %d limbs got %d", 2*emfp.NbLimbs(), len(outputs))
  }
- msg := recompose(inputs[:emfr.NbLimbs()], emfr.BitsPerLimb())
+ msg, r, s := new(big.Int), new(big.Int), new(big.Int)
+ err := limbs.Recompose(inputs[:emfr.NbLimbs()], emfr.BitsPerLimb(), msg)
+ if err != nil {
+ return fmt.Errorf("recompose message: %w", err)
+ }
  v := inputs[emfr.NbLimbs()].Uint64()
- r := recompose(inputs[emfr.NbLimbs()+1:2*emfr.NbLimbs()+1], emfr.BitsPerLimb())
- s := recompose(inputs[2*emfr.NbLimbs()+1:3*emfr.NbLimbs()+1], emfr.BitsPerLimb())
+ err = limbs.Recompose(inputs[emfr.NbLimbs()+1:2*emfr.NbLimbs()+1], emfr.BitsPerLimb(), r)
+ if err != nil {
+ return fmt.Errorf("recompose r: %w", err)
+ }
+ err = limbs.Recompose(inputs[2*emfr.NbLimbs()+1:3*emfr.NbLimbs()+1], emfr.BitsPerLimb(), s)
+ if err != nil {
+ return fmt.Errorf("recompose s: %w", err)
+ }
  var pk ecdsa.PublicKey
  var isQNRFailure int
  if err := pk.RecoverFrom(msg.Bytes(), uint(v), r, s); err != nil {
@@ -62,10 +73,10 @@ func recoverPublicKeyHint(_ *big.Int, inputs []*big.Int, outputs []*big.Int) err
  }
  Px := pk.A.X.BigInt(new(big.Int))
  Py := pk.A.Y.BigInt(new(big.Int))
- if err := decompose(Px, emfp.BitsPerLimb(), outputs[0:emfp.NbLimbs()]); err != nil {
+ if err := limbs.Decompose(Px, emfp.BitsPerLimb(), outputs[0:emfp.NbLimbs()]); err != nil {
  return fmt.Errorf("decompose x: %w", err)
  }
- if err := decompose(Py, emfp.BitsPerLimb(), outputs[emfp.NbLimbs():2*emfp.NbLimbs()]); err != nil {
+ if err := limbs.Decompose(Py, emfp.BitsPerLimb(), outputs[emfp.NbLimbs():2*emfp.NbLimbs()]); err != nil {
  return fmt.Errorf("decompose y: %w", err)
  }
  // we also return a flag that indicates if the public key is zero but only

std/gkr/api.go

@@ -2,7 +2,7 @@ package gkr
 
 import (
  "github.com/consensys/gnark/constraint"
- "github.com/consensys/gnark/std/utils/algo_utils"
+ "github.com/consensys/gnark/internal/algo_utils"
 )
 
 func frontendVarToInt(a constraint.GkrVariable) int {

std/gkr/api_test.go

@@ -2,18 +2,19 @@ package gkr
 
 import (
  "fmt"
+ "hash"
+ "math/rand"
+ "strconv"
+ "testing"
+ "time"
+
  bls12377 "github.com/consensys/gnark/constraint/bls12-377"
  bls12381 "github.com/consensys/gnark/constraint/bls12-381"
  bls24315 "github.com/consensys/gnark/constraint/bls24-315"
  bls24317 "github.com/consensys/gnark/constraint/bls24-317"
  bw6633 "github.com/consensys/gnark/constraint/bw6-633"
  bw6761 "github.com/consensys/gnark/constraint/bw6-761"
  "github.com/consensys/gnark/test"
- "hash"
- "math/rand"
- "strconv"
- "testing"
- "time"
 
  "github.com/consensys/gnark-crypto/kzg"
  "github.com/consensys/gnark/backend/plonk"
@@ -32,7 +33,7 @@ import (
  "github.com/consensys/gnark/frontend/cs/scs"
  stdHash "github.com/consensys/gnark/std/hash"
  "github.com/consensys/gnark/std/hash/mimc"
- test_vector_utils "github.com/consensys/gnark/std/utils/test_vectors_utils"
+ test_vector_utils "github.com/consensys/gnark/std/internal/test_vectors_utils"
  "github.com/consensys/gnark/test/unsafekzg"
 )
 

std/gkr/compile.go

@@ -7,9 +7,9 @@ import (
  "github.com/consensys/gnark/constraint"
  "github.com/consensys/gnark/constraint/solver"
  "github.com/consensys/gnark/frontend"
+ "github.com/consensys/gnark/internal/algo_utils"
  fiatshamir "github.com/consensys/gnark/std/fiat-shamir"
  "github.com/consensys/gnark/std/hash"
- "github.com/consensys/gnark/std/utils/algo_utils"
 )
 
 type circuitDataForSnark struct {

std/internal/limbcomposition/composition.go

@@ -0,0 +1,54 @@
+package limbs
+
+import (
+ "fmt"
+ "math/big"
+)
+
+// Recompose takes the limbs in inputs and combines them into res. It errors if
+// inputs is uninitialized or zero-length and if the result is uninitialized.
+//
+// The following holds
+//
+// res = \sum_{i=0}^{len(inputs)} inputs[i] * 2^{nbBits * i}
+func Recompose(inputs []*big.Int, nbBits uint, res *big.Int) error {
+ if len(inputs) == 0 {
+ return fmt.Errorf("zero length slice input")
+ }
+ if res == nil {
+ return fmt.Errorf("result not initialized")
+ }
+ res.SetUint64(0)
+ for i := range inputs {
+ res.Lsh(res, nbBits)
+ res.Add(res, inputs[len(inputs)-i-1])
+ }
+ // we do not mod-reduce here as the result is mod-reduced by the caller if
+ // needed. In some places we need non-reduced results.
+ return nil
+}
+
+// Decompose decomposes the input into res as integers of width nbBits. It
+// errors if the decomposition does not fit into res or if res is uninitialized.
+//
+// The following holds
+//
+// input = \sum_{i=0}^{len(res)} res[i] * 2^{nbBits * i}
+func Decompose(input *big.Int, nbBits uint, res []*big.Int) error {
+ // limb modulus
+ if input.BitLen() > len(res)*int(nbBits) {
+ return fmt.Errorf("decomposed integer does not fit into res")
+ }
+ for _, r := range res {
+ if r == nil {
+ return fmt.Errorf("result slice element uninitalized")
+ }
+ }
+ base := new(big.Int).Lsh(big.NewInt(1), nbBits)
+ tmp := new(big.Int).Set(input)
+ for i := 0; i < len(res); i++ {
+ res[i].Mod(tmp, base)
+ tmp.Rsh(tmp, nbBits)
+ }
+ return nil
+}