crypto: add btcec fallback for sign/recover without cgo (#3680)

* vendor: add github.com/btcsuite/btcd/btcec

* crypto: add btcec fallback for sign/recover without cgo

This commit adds a non-cgo fallback implementation of secp256k1
operations.

* crypto, core/vm: remove wrappers for sha256, ripemd160

2 files changed, 1 insertions, 32 deletions

diff --git a/p2p/discv5/crypto.go b/p2p/discv5/crypto.go
deleted file mode 100644
index 48b2a8a72..000000000
--- a/p2p/discv5/crypto.go
+++ /dev/null
@@ -1,31 +0,0 @@
-// Copyright 2016 The go-ethereum Authors
-// This file is part of the go-ethereum library.
-//
-// The go-ethereum library is free software: you can redistribute it and/or modify
-// it under the terms of the GNU Lesser General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// The go-ethereum library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU Lesser General Public License for more details.
-//
-// You should have received a copy of the GNU Lesser General Public License
-// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
-
-package discv5
-
-import (
-	//"github.com/btcsuite/btcd/btcec"
-	"github.com/ethereum/go-ethereum/crypto/secp256k1"
-)
-
-func S256() *secp256k1.BitCurve {
-	return secp256k1.S256()
-}
-
-// This version should be used for NaCl compilation
-/*func S256() *btcec.KoblitzCurve {
-	return S256()
-}*/
diff --git a/p2p/discv5/node.go b/p2p/discv5/node.go
index cfc833ff5..c99b4da14 100644
--- a/p2p/discv5/node.go
+++ b/p2p/discv5/node.go
@@ -297,7 +297,7 @@ func PubkeyID(pub *ecdsa.PublicKey) NodeID {
 // Pubkey returns the public key represented by the node ID.
 // It returns an error if the ID is not a point on the curve.
 func (id NodeID) Pubkey() (*ecdsa.PublicKey, error) {
-	p := &ecdsa.PublicKey{Curve: S256(), X: new(big.Int), Y: new(big.Int)}
+	p := &ecdsa.PublicKey{Curve: crypto.S256(), X: new(big.Int), Y: new(big.Int)}
 	half := len(id) / 2
 	p.X.SetBytes(id[:half])
 	p.Y.SetBytes(id[half:])