From b7bcfaaa1b7a349acb2d055a2a35a345154f7751 Mon Sep 17 00:00:00 2001
From: Abhishek Chadha <abhishekchadha235@gmail.com>
Date: Thu, 9 May 2019 22:44:37 -0700
Subject: [PATCH] scaffold

---
 core/vm/contracts.go          | 19 +++++++++++
 crypto/ed25519/ed25519.go     | 62 +++++++++++++++++++++++++++++++++++
 crypto/ed25519/ed2551_test.go |  7 ++++
 params/protocol_params.go     |  1 +
 4 files changed, 89 insertions(+)
 create mode 100644 crypto/ed25519/ed25519.go
 create mode 100644 crypto/ed25519/ed2551_test.go

diff --git a/core/vm/contracts.go b/core/vm/contracts.go
index 20b741f8f1..0396a1d5ba 100644
--- a/core/vm/contracts.go
+++ b/core/vm/contracts.go
@@ -44,6 +44,7 @@ var PrecompiledContractsHomestead = map[common.Address]PrecompiledContract{
 	common.BytesToAddress([]byte{2}): &sha256hash{},
 	common.BytesToAddress([]byte{3}): &ripemd160hash{},
 	common.BytesToAddress([]byte{4}): &dataCopy{},
+	common.BytesToAddress([]byte{5}): &ecrecovered25519{},
 }
 
 // PrecompiledContractsByzantium contains the default set of pre-compiled Ethereum
@@ -101,6 +102,24 @@ func (c *ecrecover) Run(input []byte) ([]byte, error) {
 	return common.LeftPadBytes(crypto.Keccak256(pubKey[1:])[12:], 32), nil
 }
 
+// ECRECOVER_EDDSA implemented as a native contract for Web Authentication support
+type ecrecovered25519 struct{}
+
+func (c *ecrecovered25519) RequiredGas(input []byte) uint64 {
+	return params.EcrecoverEd25519Gas
+}
+
+func (c *ecrecovered25519) Run(input []byte) ([]byte, error) {
+	/**
+		TODO: Read these real good and write this code proper
+		https://godoc.org/golang.org/x/crypto/ed25519
+		https://ed25519.cr.yp.to/
+
+	**/
+	var pubKey []byte
+	return pubKey, nil
+}
+
 // SHA256 implemented as a native contract.
 type sha256hash struct{}
 
diff --git a/crypto/ed25519/ed25519.go b/crypto/ed25519/ed25519.go
new file mode 100644
index 0000000000..f27870de45
--- /dev/null
+++ b/crypto/ed25519/ed25519.go
@@ -0,0 +1,62 @@
+package ed25519
+
+import (
+	"errors"
+	"math/big"
+)
+
+func init() {
+}
+
+var (
+	ErrInvalidMsgLen       = errors.New("invalid message length, need 32 bytes")
+	ErrInvalidSignatureLen = errors.New("invalid signature length")
+	ErrInvalidRecoveryID   = errors.New("invalid signature recovery id")
+	ErrInvalidKey          = errors.New("invalid private key")
+	ErrInvalidPubkey       = errors.New("invalid public key")
+	ErrSignFailed          = errors.New("signing failed")
+	ErrRecoverFailed       = errors.New("recovery failed")
+)
+
+// Sign creates a recoverable ed25519 signature.
+// The produced signature is in the 65-byte [R || S || V] format where V is 0 or 1.
+//
+// The caller is responsible for ensuring that msg cannot be chosen
+// directly by an attacker. It is usually preferable to use a cryptographic
+// hash function on any input before handing it to this function.
+func Sign(msg []byte, seckey []byte) ([]byte, error) {
+	// Lets just use golang.org/x/crypto/ed25519 ??
+	var sig []byte
+	return sig, nil
+}
+
+// RecoverPubkey returns the public key of the signer.
+// msg must be the 32-byte hash of the message to be signed.
+// sig must be a 65-byte compact ECDSA signature containing the
+// recovery id as the last element.
+func RecoverPubkey(msg []byte, sig []byte) ([]byte, error) {
+	var pubkey []byte
+	return pubkey, nil
+}
+
+// VerifySignature checks that the given pubkey created signature over message.
+// The signature should be in [R || S] format.
+func VerifySignature(pubkey, msg, signature []byte) bool {
+	return false
+}
+
+func checkSignature(sig []byte) error {
+	return nil
+}
+
+// DecompressPubkey parses a public key in the 33-byte compressed format.
+// It returns non-nil coordinates if the public key is valid.
+func DecompressPubkey(pubkey []byte) (x, y *big.Int) {
+	return nil, nil
+}
+
+// CompressPubkey encodes a public key to 33-byte compressed format.
+func CompressPubkey(x, y *big.Int) []byte {
+	var compressedKey []byte
+	return compressedKey
+}
diff --git a/crypto/ed25519/ed2551_test.go b/crypto/ed25519/ed2551_test.go
new file mode 100644
index 0000000000..8ab020ce3b
--- /dev/null
+++ b/crypto/ed25519/ed2551_test.go
@@ -0,0 +1,7 @@
+package ed25519
+
+import "testing"
+
+func TestSignatureValidity(t *testing.T) {
+	t.Error("Unimplemented")
+}
diff --git a/params/protocol_params.go b/params/protocol_params.go
index 14750f6a1a..a0552224c3 100644
--- a/params/protocol_params.go
+++ b/params/protocol_params.go
@@ -74,6 +74,7 @@ const (
 	// Precompiled contract gas prices
 
 	EcrecoverGas            uint64 = 3000   // Elliptic curve sender recovery gas price
+	EcrecoverEd25519Gas     uint64 = 3000   // Ed25519Gas Elliptic curve (not sender) recovery gas price - TODO: decide this value
 	Sha256BaseGas           uint64 = 60     // Base price for a SHA256 operation
 	Sha256PerWordGas        uint64 = 12     // Per-word price for a SHA256 operation
 	Ripemd160BaseGas        uint64 = 600    // Base price for a RIPEMD160 operation