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signatures/common/proof_committed_builder.go

@@ -0,0 +1,89 @@
+//
+// Copyright Coinbase, Inc. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package common
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/sonr-io/sonr/crypto/core/curves"
+)
+
+const limit = 65535
+
+// ProofCommittedBuilder is used to create
+// proofs from multiple commitments where
+// each secret is committed with a random blinding factor
+// and turned into a Schnorr proof
+type ProofCommittedBuilder struct {
+	points  []curves.Point
+	scalars []curves.Scalar
+	curve   *curves.Curve
+}
+
+// NewProofCommittedBuilder creates a new builder using the specified curve
+func NewProofCommittedBuilder(curve *curves.Curve) *ProofCommittedBuilder {
+	return &ProofCommittedBuilder{
+		points:  []curves.Point{},
+		scalars: []curves.Scalar{},
+		curve:   curve,
+	}
+}
+
+// CommitRandom uses the specified point and commits a random value to it
+func (pcb *ProofCommittedBuilder) CommitRandom(point curves.Point, reader io.Reader) error {
+	if len(pcb.points) > limit {
+		return fmt.Errorf("limit for commitments reached")
+	}
+	pcb.points = append(pcb.points, point)
+	pcb.scalars = append(pcb.scalars, pcb.curve.Scalar.Random(reader))
+	return nil
+}
+
+// Commit uses the specified point and scalar to create a commitment
+func (pcb *ProofCommittedBuilder) Commit(point curves.Point, scalar curves.Scalar) error {
+	if len(pcb.points) > limit {
+		return fmt.Errorf("limit for commitments reached")
+	}
+	pcb.points = append(pcb.points, point)
+	pcb.scalars = append(pcb.scalars, scalar)
+	return nil
+}
+
+// Get returns the point and scalar at the specified index
+func (pcb *ProofCommittedBuilder) Get(index int) (curves.Point, curves.Scalar) {
+	if index >= len(pcb.points) || index < 0 {
+		return nil, nil
+	}
+	return pcb.points[index], pcb.scalars[index]
+}
+
+// GetChallengeContribution returns the bytes that should be added to
+// a sigma protocol transcript for generating the challenge
+func (pcb ProofCommittedBuilder) GetChallengeContribution() []byte {
+	commitment := pcb.curve.Point.SumOfProducts(pcb.points, pcb.scalars)
+	if commitment == nil {
+		return nil
+	}
+	return commitment.ToAffineCompressed()
+}
+
+// GenerateProof converts the blinding factors and secrets into Schnorr proofs
+func (pcb ProofCommittedBuilder) GenerateProof(
+	challenge curves.Scalar,
+	secrets []curves.Scalar,
+) ([]curves.Scalar, error) {
+	if len(secrets) != len(pcb.scalars) {
+		return nil, fmt.Errorf("secrets is not equal to blinding factors")
+	}
+
+	proofs := make([]curves.Scalar, len(pcb.scalars))
+	for i, sc := range pcb.scalars {
+		proofs[i] = secrets[i].MulAdd(challenge, sc)
+	}
+	return proofs, nil
+}