crypto: add secp256k1 implementation

Part of #1003

We have to implement Koblitz-related math to recover keys properly
with Neo.Cryptography.Secp256k1Recover interop as far as standard
go elliptic package supports short-form Weierstrass curve with a=-3
only (see golang/go#26776 for details).
However, it's not the best choise to have a lot of such math in our
project, so it would be better to use ready-made solution for
Koblitz-related cryptography.

go.mod

@@ -3,6 +3,7 @@ module github.com/nspcc-dev/neo-go
 require (
 	github.com/Workiva/go-datastructures v1.0.50
 	github.com/alicebob/miniredis v2.5.0+incompatible
+	github.com/btcsuite/btcd v0.20.1-beta
 	github.com/dgraph-io/badger/v2 v2.0.3
 	github.com/go-redis/redis v6.10.2+incompatible
 	github.com/go-yaml/yaml v2.1.0+incompatible

go.sum

@@ -13,6 +13,8 @@ github.com/abiosoft/ishell v2.0.0+incompatible h1:zpwIuEHc37EzrsIYah3cpevrIc8Oma
 github.com/abiosoft/ishell v2.0.0+incompatible/go.mod h1:HQR9AqF2R3P4XXpMpI0NAzgHf/aS6+zVXRj14cVk9qg=
 github.com/abiosoft/readline v0.0.0-20180607040430-155bce2042db h1:CjPUSXOiYptLbTdr1RceuZgSFDQ7U15ITERUGrUORx8=
 github.com/abiosoft/readline v0.0.0-20180607040430-155bce2042db/go.mod h1:rB3B4rKii8V21ydCbIzH5hZiCQE7f5E9SzUb/ZZx530=
+github.com/aead/siphash v1.0.1 h1:FwHfE/T45KPKYuuSAKyyvE+oPWcaQ+CUmFW0bPlM+kg=
+github.com/aead/siphash v1.0.1/go.mod h1:Nywa3cDsYNNK3gaciGTWPwHt0wlpNV15vwmswBAUSII=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751 h1:JYp7IbQjafoB+tBA3gMyHYHrpOtNuDiK/uB5uXxq5wM=
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
@@ -28,6 +30,22 @@ github.com/beorn7/perks v0.0.0-20180321164747-3a771d992973/go.mod h1:Dwedo/Wpr24
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/btcsuite/btcd v0.20.1-beta h1:Ik4hyJqN8Jfyv3S4AGBOmyouMsYE3EdYODkMbQjwPGw=
+github.com/btcsuite/btcd v0.20.1-beta/go.mod h1:wVuoA8VJLEcwgqHBwHmzLRazpKxTv13Px/pDuV7OomQ=
+github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f h1:bAs4lUbRJpnnkd9VhRV3jjAVU7DJVjMaK+IsvSeZvFo=
+github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f/go.mod h1:TdznJufoqS23FtqVCzL0ZqgP5MqXbb4fg/WgDys70nA=
+github.com/btcsuite/btcutil v0.0.0-20190425235716-9e5f4b9a998d h1:yJzD/yFppdVCf6ApMkVy8cUxV0XrxdP9rVf6D87/Mng=
+github.com/btcsuite/btcutil v0.0.0-20190425235716-9e5f4b9a998d/go.mod h1:+5NJ2+qvTyV9exUAL/rxXi3DcLg2Ts+ymUAY5y4NvMg=
+github.com/btcsuite/go-socks v0.0.0-20170105172521-4720035b7bfd h1:R/opQEbFEy9JGkIguV40SvRY1uliPX8ifOvi6ICsFCw=
+github.com/btcsuite/go-socks v0.0.0-20170105172521-4720035b7bfd/go.mod h1:HHNXQzUsZCxOoE+CPiyCTO6x34Zs86zZUiwtpXoGdtg=
+github.com/btcsuite/goleveldb v0.0.0-20160330041536-7834afc9e8cd h1:qdGvebPBDuYDPGi1WCPjy1tGyMpmDK8IEapSsszn7HE=
+github.com/btcsuite/goleveldb v0.0.0-20160330041536-7834afc9e8cd/go.mod h1:F+uVaaLLH7j4eDXPRvw78tMflu7Ie2bzYOH4Y8rRKBY=
+github.com/btcsuite/snappy-go v0.0.0-20151229074030-0bdef8d06723 h1:ZA/jbKoGcVAnER6pCHPEkGdZOV7U1oLUedErBHCUMs0=
+github.com/btcsuite/snappy-go v0.0.0-20151229074030-0bdef8d06723/go.mod h1:8woku9dyThutzjeg+3xrA5iCpBRH8XEEg3lh6TiUghc=
+github.com/btcsuite/websocket v0.0.0-20150119174127-31079b680792 h1:R8vQdOQdZ9Y3SkEwmHoWBmX1DNXhXZqlTpq6s4tyJGc=
+github.com/btcsuite/websocket v0.0.0-20150119174127-31079b680792/go.mod h1:ghJtEyQwv5/p4Mg4C0fgbePVuGr935/5ddU9Z3TmDRY=
+github.com/btcsuite/winsvc v1.0.0 h1:J9B4L7e3oqhXOcm+2IuNApwzQec85lE+QaikUcCs+dk=
+github.com/btcsuite/winsvc v1.0.0/go.mod h1:jsenWakMcC0zFBFurPLEAyrnc/teJEM1O46fmI40EZs=
 github.com/cespare/xxhash v1.1.0 h1:a6HrQnmkObjyL+Gs60czilIUGqrzKutQD6XZog3p+ko=
 github.com/cespare/xxhash v1.1.0/go.mod h1:XrSqR1VqqWfGrhpAt58auRo0WTKS1nRRg3ghfAqPWnc=
 github.com/cespare/xxhash/v2 v2.1.0 h1:yTUvW7Vhb89inJ+8irsUqiWjh8iT6sQPZiQzI6ReGkA=
@@ -41,6 +59,7 @@ github.com/coreos/etcd v3.3.10+incompatible/go.mod h1:uF7uidLiAD3TWHmW31ZFd/JWoc
 github.com/coreos/go-etcd v2.0.0+incompatible/go.mod h1:Jez6KQU2B/sWsbdaef3ED8NzMklzPG4d5KIOhIy30Tk=
 github.com/coreos/go-semver v0.2.0/go.mod h1:nnelYz7RCh+5ahJtPPxZlU+153eP4D4r3EedlOD2RNk=
 github.com/cpuguy83/go-md2man v1.0.10/go.mod h1:SmD6nW6nTyfqj6ABTjUi3V3JVMnlJmwcJI5acqYI6dE=
+github.com/davecgh/go-spew v0.0.0-20171005155431-ecdeabc65495/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
@@ -91,9 +110,15 @@ github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T
 github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
 github.com/inconshreveable/mousetrap v1.0.0/go.mod h1:PxqpIevigyE2G7u3NXJIT2ANytuPF1OarO4DADm73n8=
+github.com/jessevdk/go-flags v0.0.0-20141203071132-1679536dcc89 h1:12K8AlpT0/6QUXSfV0yi4Q0jkbq8NDtIKFtF61AoqV0=
+github.com/jessevdk/go-flags v0.0.0-20141203071132-1679536dcc89/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
+github.com/jrick/logrotate v1.0.0 h1:lQ1bL/n9mBNeIXoTUoYRlK4dHuNJVofX9oWqBtPnSzI=
+github.com/jrick/logrotate v1.0.0/go.mod h1:LNinyqDIJnpAur+b8yyulnQw/wDuN1+BYKlTRt3OuAQ=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
 github.com/json-iterator/go v1.1.7/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
 github.com/julienschmidt/httprouter v1.2.0/go.mod h1:SYymIcj16QtmaHHD7aYtjjsJG7VTCxuUUipMqKk8s4w=
+github.com/kkdai/bstream v0.0.0-20161212061736-f391b8402d23 h1:FOOIBWrEkLgmlgGfMuZT83xIwfPDxEI2OHu6xUmJMFE=
+github.com/kkdai/bstream v0.0.0-20161212061736-f391b8402d23/go.mod h1:J+Gs4SYgM6CZQHDETBtE9HaSEkGmuNXF86RwHhHUvq4=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1 h1:mweAR1A6xJ3oS2pRaGiHgQ4OO8tzTaLawm8vnODuwDk=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515/go.mod h1:+0opPa2QZZtGFBFZlji/RkVcI2GknAs/DXo4wKdlNEc=
@@ -144,10 +169,12 @@ github.com/nspcc-dev/rfc6979 v0.2.0 h1:3e1WNxrN60/6N0DW7+UYisLeZJyfqZTNOjeV/toYv
 github.com/nspcc-dev/rfc6979 v0.2.0/go.mod h1:exhIh1PdpDC5vQmyEsGvc4YDM/lyQp/452QxGq/UEso=
 github.com/onsi/ginkgo v1.6.0 h1:Ix8l273rp3QzYgXSR+c8d1fTG7UPgYkOSELPhiY/YGw=
 github.com/onsi/ginkgo v1.6.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
+github.com/onsi/ginkgo v1.7.0/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/ginkgo v1.10.3 h1:OoxbjfXVZyod1fmWYhI7SEyaD8B00ynP3T+D5GiyHOY=
 github.com/onsi/ginkgo v1.10.3/go.mod h1:lLunBs/Ym6LB5Z9jYTR76FiuTmxDTDusOGeTQH+WWjE=
 github.com/onsi/gomega v1.4.2 h1:3mYCb7aPxS/RU7TI1y4rkEn1oKmPRjNJLNEXgw7MH2I=
 github.com/onsi/gomega v1.4.2/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
+github.com/onsi/gomega v1.4.3/go.mod h1:ex+gbHU/CVuBBDIJjb2X0qEXbFg53c61hWP/1CpauHY=
 github.com/onsi/gomega v1.7.1 h1:K0jcRCwNQM3vFGh1ppMtDh/+7ApJrjldlX8fA0jDTLQ=
 github.com/onsi/gomega v1.7.1/go.mod h1:XdKZgCCFLUoM/7CFJVPcG8C1xQ1AJ0vpAezJrB7JYyY=
 github.com/pelletier/go-toml v1.2.0/go.mod h1:5z9KED0ma1S8pY6P1sdut58dfprrGBbd/94hg7ilaic=
@@ -212,6 +239,7 @@ go.uber.org/multierr v1.1.0 h1:HoEmRHQPVSqub6w2z2d2EOVs2fjyFRGyofhKuyDq0QI=
 go.uber.org/multierr v1.1.0/go.mod h1:wR5kodmAFQ0UK8QlbwjlSNy0Z68gJhDJUG5sjR94q/0=
 go.uber.org/zap v1.10.0 h1:ORx85nbTijNz8ljznvCMR1ZBIPKFn3jQrag10X2AsuM=
 go.uber.org/zap v1.10.0/go.mod h1:vwi/ZaCAaUcBkycHslxD9B2zi4UTXhF60s6SWpuDF0Q=
+golang.org/x/crypto v0.0.0-20170930174604-9419663f5a44/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20181203042331-505ab145d0a9/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 h1:VklqNMn3ovrHsnt90PveolxSbWFaJdECFbxSq0Mqo2M=

pkg/core/interop_neo.go

@@ -7,6 +7,8 @@ import (
 	"math"
 	"math/big"
 
+	"github.com/btcsuite/btcd/btcec"
+
 	"github.com/nspcc-dev/neo-go/pkg/core/state"
 	"github.com/nspcc-dev/neo-go/pkg/core/storage"
 	"github.com/nspcc-dev/neo-go/pkg/core/transaction"
@@ -604,7 +606,7 @@ func (ic *interopContext) contractMigrate(v *vm.VM) error {
 
 // secp256k1Recover recovers speck256k1 public key.
 func (ic *interopContext) secp256k1Recover(v *vm.VM) error {
-	return ic.eccRecover(keys.Secp256k1(), v)
+	return ic.eccRecover(btcec.S256(), v)
 }
 
 // secp256r1Recover recovers speck256r1 public key.

pkg/crypto/keys/publickey.go

@@ -10,6 +10,8 @@ import (
 	"fmt"
 	"math/big"
 
+	"github.com/btcsuite/btcd/btcec"
+
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/encoding/address"
 	"github.com/nspcc-dev/neo-go/pkg/io"
@@ -142,15 +144,11 @@ func NewPublicKeyFromASN1(data []byte) (*PublicKey, error) {
 // where `p` denotes the order of the underlying curve field
 func decodeCompressedY(x *big.Int, ylsb uint, curve elliptic.Curve) (*big.Int, error) {
 	var a *big.Int
-	switch curve.Params().Name {
-	case Secp256k1Curve:
+	switch curve.(type) {
+	case *btcec.KoblitzCurve:
 		a = big.NewInt(0)
-	case elliptic.P256().Params().Name:
-		a = big.NewInt(3)
 	default:
-		// actually, we do support all curves from standard elliptic package as far as
-		// these curves have a=-3 which is hard-coded in the package
-		return nil, errors.New("Secp256k1 and Secp256r1 are only supported")
+		a = big.NewInt(3)
 	}
 	cp := curve.Params()
 	xCubed := new(big.Int).Exp(x, big.NewInt(3), cp.P)
@@ -357,9 +355,6 @@ func KeyRecover(curve elliptic.Curve, r, s *big.Int, messageHash []byte, isEven
 		}
 
 		// step 1.4: check n*R is point at infinity
-		// TODO: curve.ScalarMult suppose we're dealing with a=-3 in the elliptic curve equation.
-		// This line will give wrong results for secp256k1 unless we define our own implementation
-		// of ScalarMult for secp256k1 curve with a=0.
 		nRx, nR := curve.ScalarMult(Rx, R, params.N.Bytes())
 		if nRx.Sign() != 0 || nR.Sign() != 0 {
 			continue
@@ -373,16 +368,13 @@ func KeyRecover(curve elliptic.Curve, r, s *big.Int, messageHash []byte, isEven
 		// first term.
 		invrS := new(big.Int).Mul(invr, s)
 		invrS.Mod(invrS, params.N)
-		// TODO: implement ScalarMult for secp256k1
 		sRx, sR := curve.ScalarMult(Rx, R, invrS.Bytes())
 		// second term.
 		e.Neg(e)
 		e.Mod(e, params.N)
 		e.Mul(e, invr)
 		e.Mod(e, params.N)
-		// TODO: it won't be difficult to implement ScalarBaseMult having ScalarMult for secp256k1.
 		minuseGx, minuseGy := curve.ScalarBaseMult(e.Bytes())
-		// TODO: the same thing for secp256k1.
 		Qx, Qy := curve.Add(sRx, sR, minuseGx, minuseGy)
 		res.X = Qx
 		res.Y = Qy

pkg/crypto/keys/publickey_test.go

@@ -9,6 +9,10 @@ import (
 	"sort"
 	"testing"
 
+	"github.com/nspcc-dev/neo-go/pkg/util"
+
+	"github.com/btcsuite/btcd/btcec"
+
 	"github.com/nspcc-dev/neo-go/pkg/crypto/hash"
 	"github.com/nspcc-dev/neo-go/pkg/internal/testserdes"
 	"github.com/stretchr/testify/require"
@@ -184,7 +188,7 @@ func TestUnmarshallJSONBadFormat(t *testing.T) {
 }
 
 func TestRecoverSecp256r1Static(t *testing.T) {
-	//these data were taken from reference testcase
+	//these data were taken from the reference testcase
 	b := []byte{123, 245, 126, 56, 3, 123, 197, 199, 26, 31, 212, 186, 120, 195, 168, 153, 57, 108, 234, 49, 107, 203, 44, 207, 185, 212, 187, 129, 74, 43, 225, 69}
 	privateKey, err := NewPrivateKeyFromBytes(b)
 	require.NoError(t, err)
@@ -212,3 +216,36 @@ func TestRecoverSecp256r1(t *testing.T) {
 	require.NoError(t, err)
 	require.True(t, privateKey.PublicKey().Equal(&recoveredKey))
 }
+
+func TestRecoverSecp256k1Static(t *testing.T) {
+	//these data were taken from the reference testcase
+	b := []byte{156, 3, 247, 58, 246, 250, 236, 27, 118, 60, 180, 177, 18, 92, 204, 206, 144, 245, 148, 141, 86, 212, 151, 181, 15, 113, 172, 180, 177, 228, 100, 32}
+	_, publicKey := btcec.PrivKeyFromBytes(btcec.S256(), b)
+	message := []byte{72, 101, 108, 108, 111, 87, 111, 114, 108, 100}
+	r := new(big.Int).SetBytes(util.ArrayReverse([]byte{50, 100, 228, 9, 6, 57, 227, 27, 91, 215, 47, 90, 65, 225, 81, 110, 36, 58, 250, 57, 77, 176, 108, 67, 46, 180, 184, 210, 111, 242, 169, 88}))
+	s := new(big.Int).SetBytes(util.ArrayReverse([]byte{197, 79, 96, 98, 232, 38, 165, 214, 98, 66, 137, 113, 98, 15, 167, 149, 45, 46, 207, 232, 116, 136, 36, 184, 241, 212, 181, 17, 190, 81, 150, 86}))
+	signature := btcec.Signature{
+		R: r,
+		S: s,
+	}
+	// just ensure it's a valid signature
+	require.True(t, signature.Verify(message, publicKey))
+	recoveredKey, err := KeyRecover(btcec.S256(), r, s, message, false)
+	require.NoError(t, err)
+	require.True(t, new(big.Int).SetBytes([]byte{112, 186, 29, 131, 169, 21, 212, 95, 81, 172, 201, 145, 168, 108, 129, 90, 6, 111, 80, 39, 136, 157, 15, 181, 98, 108, 133, 108, 144, 80, 23, 225}).Cmp(recoveredKey.X) == 0)
+	require.True(t, new(big.Int).SetBytes([]byte{187, 102, 202, 42, 152, 133, 222, 55, 137, 228, 154, 80, 182, 35, 133, 14, 55, 165, 36, 64, 178, 55, 13, 112, 224, 143, 66, 143, 208, 18, 2, 211}).Cmp(recoveredKey.Y) == 0)
+}
+
+func TestRecoverSecp256k1(t *testing.T) {
+	privateKey, err := btcec.NewPrivateKey(btcec.S256())
+	message := []byte{72, 101, 108, 108, 111, 87, 111, 114, 108, 100}
+	signature, err := privateKey.Sign(message)
+	require.NoError(t, err)
+	require.True(t, signature.Verify(message, privateKey.PubKey()))
+	// TODO: to test this properly, we should provide correct isEven flag. This flag denotes which one of
+	// the two recovered R points in decodeCompressedY method should be chosen.
+	recoveredKey, err := KeyRecover(btcec.S256(), signature.R, signature.S, message, false)
+	require.NoError(t, err)
+	require.True(t, privateKey.PubKey().X.Cmp(recoveredKey.X) == 0)
+	require.True(t, privateKey.PubKey().Y.Cmp(recoveredKey.Y) == 0)
+}