Update dependencies

vendor/github.com/hdevalence/ed25519consensus/ed25519.go

@@ -0,0 +1,67 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Copyright 2016 Henry de Valence. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ed25519consensus implements Ed25519 verification according to ZIP215.
+package ed25519consensus
+
+import (
+	"crypto/ed25519"
+	"crypto/sha512"
+
+	"filippo.io/edwards25519"
+)
+
+// Verify reports whether sig is a valid signature of message by
+// publicKey, using precisely-specified validation criteria (ZIP 215) suitable
+// for use in consensus-critical contexts.
+func Verify(publicKey ed25519.PublicKey, message, sig []byte) bool {
+	if l := len(publicKey); l != ed25519.PublicKeySize {
+		return false
+	}
+
+	if len(sig) != ed25519.SignatureSize || sig[63]&224 != 0 {
+		return false
+	}
+
+	// ZIP215: this works because SetBytes does not check that encodings are canonical.
+	A, err := new(edwards25519.Point).SetBytes(publicKey)
+	if err != nil {
+		return false
+	}
+	A.Negate(A)
+
+	h := sha512.New()
+	h.Write(sig[:32])
+	h.Write(publicKey[:])
+	h.Write(message)
+	var digest [64]byte
+	h.Sum(digest[:0])
+
+	hReduced, err := new(edwards25519.Scalar).SetUniformBytes(digest[:])
+	if err != nil {
+		return false
+	}
+
+	// ZIP215: this works because SetBytes does not check that encodings are canonical.
+	checkR, err := new(edwards25519.Point).SetBytes(sig[:32])
+	if err != nil {
+		return false
+	}
+
+	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
+	// the range [0, order) in order to prevent signature malleability.
+	// ZIP215: This is also required by ZIP215.
+	s, err := new(edwards25519.Scalar).SetCanonicalBytes(sig[32:])
+	if err != nil {
+		return false
+	}
+
+	R := new(edwards25519.Point).VarTimeDoubleScalarBaseMult(hReduced, A, s)
+
+	// ZIP215: We want to check [8](R - checkR) == 0
+	p := new(edwards25519.Point).Subtract(R, checkR) // p = R - checkR
+	p.MultByCofactor(p)
+	return p.Equal(edwards25519.NewIdentityPoint()) == 1 // p == 0
+}