From 5b84f9efce2b2921345180cd4121e6f4ee6331e5 Mon Sep 17 00:00:00 2001
From: Dillen Meijboom <info@excol.nl>
Date: Tue, 7 Dec 2021 15:30:25 +0100
Subject: [PATCH] Switched to P256 as default curve and fixed tests so that the
 ethereum dependency can be removed

---
 ecies_test.go | 41 ++++++++++++++---------------------------
 go.sum        |  0
 params.go     | 11 ++++-------
 3 files changed, 18 insertions(+), 34 deletions(-)
 create mode 100644 go.sum

diff --git a/ecies_test.go b/ecies_test.go
index 0a6aeb2..3275c49 100644
--- a/ecies_test.go
+++ b/ecies_test.go
@@ -31,6 +31,7 @@ package ecies
 
 import (
 	"bytes"
+	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/sha256"
@@ -38,8 +39,6 @@ import (
 	"fmt"
 	"math/big"
 	"testing"
-
-	"github.com/ethereum/go-ethereum/crypto"
 )
 
 func TestKDF(t *testing.T) {
@@ -104,10 +103,10 @@ func TestSharedKeyPadding(t *testing.T) {
 	// sanity checks
 	prv0 := hexKey("1adf5c18167d96a1f9a0b1ef63be8aa27eaf6032c233b2b38f7850cf5b859fd9")
 	prv1 := hexKey("0097a076fc7fcd9208240668e31c9abee952cbb6e375d1b8febc7499d6e16f1a")
-	x0, _ := new(big.Int).SetString("1a8ed022ff7aec59dc1b440446bdda5ff6bcb3509a8b109077282b361efffbd8", 16)
-	x1, _ := new(big.Int).SetString("6ab3ac374251f638d0abb3ef596d1dc67955b507c104e5f2009724812dc027b8", 16)
-	y0, _ := new(big.Int).SetString("e040bd480b1deccc3bc40bd5b1fdcb7bfd352500b477cb9471366dbd4493f923", 16)
-	y1, _ := new(big.Int).SetString("8ad915f2b503a8be6facab6588731fefeb584fd2dfa9a77a5e0bba1ec439e4fa", 16)
+	x0, _ := new(big.Int).SetString("894f0b45e976ff1d368ecb31aa5fdd47e3edb1b980b7d3bf7a7b543a5b2964a0", 16)
+	x1, _ := new(big.Int).SetString("99a279d52118fffbaa3f2ac2d60f3bacf10e6cf86f46ee7f3b39b29ec78a94f2", 16)
+	y0, _ := new(big.Int).SetString("c942f48766dc44c2a6e808691091de40d84f9b9df5394f6df99454a209d7843e", 16)
+	y1, _ := new(big.Int).SetString("7ca3ebd2ea8ac4913c8c0c8cac4571316abab06b2a076caa9369a1ae7fd2d8ce", 16)
 
 	if prv0.PublicKey.X.Cmp(x0) != 0 {
 		t.Errorf("mismatched prv0.X:\nhave: %x\nwant: %x\n", prv0.PublicKey.X.Bytes(), x0.Bytes())
@@ -186,21 +185,6 @@ func BenchmarkGenSharedKeyP256(b *testing.B) {
 	}
 }
 
-// Benchmark the generation of S256 shared keys.
-func BenchmarkGenSharedKeyS256(b *testing.B) {
-	prv, err := GenerateKey(rand.Reader, crypto.S256(), nil)
-	if err != nil {
-		b.Fatal(err)
-	}
-	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
-		_, err := prv.GenerateShared(&prv.PublicKey, 16, 16)
-		if err != nil {
-			b.Fatal(err)
-		}
-	}
-}
-
 // Verify that an encrypted message can be successfully decrypted.
 func TestEncryptDecrypt(t *testing.T) {
 	prv1, err := GenerateKey(rand.Reader, DefaultCurve, nil)
@@ -407,18 +391,21 @@ func TestSharedKeyStatic(t *testing.T) {
 		t.Fatal(ErrBadSharedKeys)
 	}
 
-	sk := decode("167ccc13ac5e8a26b131c3446030c60fbfac6aa8e31149d0869f93626a4cdf62")
+	sk := decode("2b71c59bb0495360d20642360998981d3d00c74f6e72ec4d94f1391662f00d10")
 	if !bytes.Equal(sk1, sk) {
 		t.Fatalf("shared secret mismatch: want: %x have: %x", sk, sk1)
 	}
 }
 
 func hexKey(prv string) *PrivateKey {
-	key, err := crypto.HexToECDSA(prv)
-	if err != nil {
-		panic(err)
-	}
-	return ImportECDSA(key)
+	b := decode(prv)
+
+	privateKey := &ecdsa.PrivateKey{}
+	privateKey.PublicKey.Curve = elliptic.P256()
+	privateKey.D = (&big.Int{}).SetBytes(b)
+	privateKey.X, privateKey.Y = privateKey.PublicKey.Curve.ScalarBaseMult(b)
+
+	return ImportECDSA(privateKey)
 }
 
 func decode(s string) []byte {
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..e69de29
diff --git a/params.go b/params.go
index 0bd3877..7a30c6c 100644
--- a/params.go
+++ b/params.go
@@ -41,12 +41,10 @@ import (
 	"crypto/sha512"
 	"fmt"
 	"hash"
-
-	ethcrypto "github.com/ethereum/go-ethereum/crypto"
 )
 
 var (
-	DefaultCurve                  = ethcrypto.S256()
+	DefaultCurve                  = elliptic.P256()
 	ErrUnsupportedECDHAlgorithm   = fmt.Errorf("ecies: unsupported ECDH algorithm")
 	ErrUnsupportedECIESParameters = fmt.Errorf("ecies: unsupported ECIES parameters")
 	ErrInvalidKeyLen              = fmt.Errorf("ecies: invalid key size (> %d) in ECIESParams", maxKeyLen)
@@ -106,10 +104,9 @@ var (
 )
 
 var paramsFromCurve = map[elliptic.Curve]*ECIESParams{
-	ethcrypto.S256(): ECIES_AES128_SHA256,
-	elliptic.P256():  ECIES_AES128_SHA256,
-	elliptic.P384():  ECIES_AES256_SHA384,
-	elliptic.P521():  ECIES_AES256_SHA512,
+	elliptic.P256(): ECIES_AES128_SHA256,
+	elliptic.P384(): ECIES_AES256_SHA384,
+	elliptic.P521(): ECIES_AES256_SHA512,
 }
 
 func AddParamsForCurve(curve elliptic.Curve, params *ECIESParams) {