vendor: update all dependencies to latest versions

vendor/golang.org/x/crypto/bn256/bn256.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package bn256 implements a particular bilinear group at the 128-bit security level.
+// Package bn256 implements a particular bilinear group.
 //
 // Bilinear groups are the basis of many of the new cryptographic protocols
 // that have been proposed over the past decade. They consist of a triplet of
@@ -14,6 +14,10 @@
 // Barreto-Naehrig curve as described in
 // http://cryptojedi.org/papers/dclxvi-20100714.pdf. Its output is compatible
 // with the implementation described in that paper.
+//
+// (This package previously claimed to operate at a 128-bit security level.
+// However, recent improvements in attacks mean that is no longer true. See
+// https://moderncrypto.org/mail-archive/curves/2016/000740.html.)
 package bn256 // import "golang.org/x/crypto/bn256"
 
 import (
@@ -49,8 +53,8 @@ func RandomG1(r io.Reader) (*big.Int, *G1, error) {
 	return k, new(G1).ScalarBaseMult(k), nil
 }
 
-func (g *G1) String() string {
-	return "bn256.G1" + g.p.String()
+func (e *G1) String() string {
+	return "bn256.G1" + e.p.String()
 }
 
 // ScalarBaseMult sets e to g*k where g is the generator of the group and
@@ -92,11 +96,11 @@ func (e *G1) Neg(a *G1) *G1 {
 }
 
 // Marshal converts n to a byte slice.
-func (n *G1) Marshal() []byte {
-	n.p.MakeAffine(nil)
+func (e *G1) Marshal() []byte {
+	e.p.MakeAffine(nil)
 
-	xBytes := new(big.Int).Mod(n.p.x, p).Bytes()
-	yBytes := new(big.Int).Mod(n.p.y, p).Bytes()
+	xBytes := new(big.Int).Mod(e.p.x, p).Bytes()
+	yBytes := new(big.Int).Mod(e.p.y, p).Bytes()
 
 	// Each value is a 256-bit number.
 	const numBytes = 256 / 8
@@ -166,8 +170,8 @@ func RandomG2(r io.Reader) (*big.Int, *G2, error) {
 	return k, new(G2).ScalarBaseMult(k), nil
 }
 
-func (g *G2) String() string {
-	return "bn256.G2" + g.p.String()
+func (e *G2) String() string {
+	return "bn256.G2" + e.p.String()
 }
 
 // ScalarBaseMult sets e to g*k where g is the generator of the group and