feat: usable placeholder hints for bn254

constraint/solver/hint_registry.go

@@ -46,6 +46,12 @@ func RegisterNamedHint(hintFn Hint, key HintID) {
 	registry[key] = hintFn
 }
 
+func RemoveNamedHint(key HintID) {
+	registryM.Lock()
+	defer registryM.Unlock()
+	delete(registry, key)
+}
+
 // GetRegisteredHints returns all registered hint functions.
 func GetRegisteredHints() []Hint {
 	registryM.RLock()

std/gkr/compile.go

@@ -164,6 +164,9 @@ func (s Solution) Export(v frontend.Variable) []frontend.Variable {
 }
 
 // Verify encodes the verification circuitry for the GKR circuit
+// hashName denotes the random oracle used to make GKR non-interactive (Fiat-Shamir)
+// initialChallenges are initially fed to the Fiat-Shamir hash. If there is many of them, use api.(Committer).Commit to
+// consolidate them into a few values
 func (s Solution) Verify(hashName string, initialChallenges ...frontend.Variable) error {
 	var (
 		err             error
@@ -206,6 +209,9 @@ func (s Solution) Verify(hashName string, initialChallenges ...frontend.Variable
 		return err
 	}
 
+	solver.RegisterNamedHint(SolveHintPlaceholderGenerator(s.toStore.SolveHintID, s.toStore), s.toStore.SolveHintID)
+	solver.RegisterNamedHint(ProveHintPlaceholderGenerator(hashName, s.toStore.SolveHintID, s.toStore.ProveHintID), s.toStore.ProveHintID)
+
 	return s.parentApi.Compiler().SetGkrInfo(s.toStore)
 }
 

std/gkr/placeholder_hints.go

@@ -0,0 +1,82 @@
+package gkr
+
+import (
+	"errors"
+	"github.com/consensys/gnark-crypto/ecc"
+	"github.com/consensys/gnark/constraint"
+	bls12_377 "github.com/consensys/gnark/constraint/bls12-377"
+	bls12_381 "github.com/consensys/gnark/constraint/bls12-381"
+	bls24_315 "github.com/consensys/gnark/constraint/bls24-315"
+	bls24_317 "github.com/consensys/gnark/constraint/bls24-317"
+	bn254 "github.com/consensys/gnark/constraint/bn254"
+	bw6_633 "github.com/consensys/gnark/constraint/bw6-633"
+	bw6_761 "github.com/consensys/gnark/constraint/bw6-761"
+
+	"github.com/consensys/gnark/constraint/solver"
+	"github.com/consensys/gnark/internal/utils"
+	"math/big"
+)
+
+// TODO @Tabaie Autogen this and possibly move to another package
+
+var placeholderGkrSolvingData map[solver.HintID]any
+
+func SolveHintPlaceholderGenerator(hintId solver.HintID, gkrInfo constraint.GkrInfo) func(*big.Int, []*big.Int, []*big.Int) error {
+	return func(mod *big.Int, in []*big.Int, out []*big.Int) (err error) {
+		solver.RemoveNamedHint(hintId)
+
+		curve := utils.FieldToCurve(mod)
+		switch curve {
+		case ecc.BLS12_377:
+			var data bls12_377.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bls12_377.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		case ecc.BLS12_381:
+			var data bls12_381.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bls12_381.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		case ecc.BLS24_315:
+			var data bls24_315.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bls24_315.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		case ecc.BLS24_317:
+			var data bls24_317.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bls24_317.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		case ecc.BN254:
+			var data bn254.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bn254.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		case ecc.BW6_633:
+			var data bw6_633.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bw6_633.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		case ecc.BW6_761:
+			var data bw6_761.GkrSolvingData
+			placeholderGkrSolvingData[hintId] = &data
+			err = bw6_761.GkrSolveHint(gkrInfo, &data)(mod, in, out)
+		default:
+			err = errors.New("unsupported curve")
+		}
+
+		return err
+	}
+}
+
+func ProveHintPlaceholderGenerator(hashName string, solveHintId, proveHintId solver.HintID) func(*big.Int, []*big.Int, []*big.Int) error {
+	return func(mod *big.Int, in []*big.Int, out []*big.Int) (err error) {
+		solver.RemoveNamedHint(proveHintId)
+
+		curve := utils.FieldToCurve(mod)
+		switch curve {
+		case ecc.BN254:
+			err = bn254.GkrProveHint(hashName, placeholderGkrSolvingData[solveHintId].(*bn254.GkrSolvingData))(mod, in, out)
+		default:
+			err = errors.New("unsupported curve")
+		}
+
+		delete(placeholderGkrSolvingData, solveHintId)
+
+		return err
+	}
+}