(no commit message provided)

crypto/ted25519/frost/challenge_derive.go

@@ -0,0 +1,27 @@
+//
+// Copyright Coinbase, Inc. All Rights Reserved.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+package frost
+
+import (
+	"crypto/sha512"
+
+	"github.com/onsonr/hway/crypto/core/curves"
+)
+
+type ChallengeDerive interface {
+	DeriveChallenge(msg []byte, pubKey curves.Point, r curves.Point) (curves.Scalar, error)
+}
+
+type Ed25519ChallengeDeriver struct{}
+
+func (ed Ed25519ChallengeDeriver) DeriveChallenge(msg []byte, pubKey curves.Point, r curves.Point) (curves.Scalar, error) {
+	h := sha512.New()
+	_, _ = h.Write(r.ToAffineCompressed())
+	_, _ = h.Write(pubKey.ToAffineCompressed())
+	_, _ = h.Write(msg)
+	return new(curves.ScalarEd25519).SetBytesWide(h.Sum(nil))
+}