From 16d89e0d7b1b7696ef00f0c6677295668d97def7 Mon Sep 17 00:00:00 2001
From: Marius van der Wijden <m.vanderwijden@live.de>
Date: Fri, 15 Mar 2024 11:57:18 +0100
Subject: [PATCH] crypto: hide BitCurve behind interface again

---
 crypto/ecies/ecies.go   | 13 ++++---------
 crypto/signature_cgo.go | 12 +++++++++++-
 p2p/rlpx/rlpx.go        |  6 +-----
 3 files changed, 16 insertions(+), 15 deletions(-)

diff --git a/crypto/ecies/ecies.go b/crypto/ecies/ecies.go
index 688a223b40..bd7ab1d583 100644
--- a/crypto/ecies/ecies.go
+++ b/crypto/ecies/ecies.go
@@ -40,6 +40,8 @@ import (
 	"hash"
 	"io"
 	"math/big"
+
+	"github.com/ethereum/go-ethereum/crypto"
 )
 
 var (
@@ -255,11 +257,7 @@ func Encrypt(rand io.Reader, pub *PublicKey, m, s1, s2 []byte) (ct []byte, err e
 
 	d := messageTag(params.Hash, Km, em, s2)
 
-	type marshaller interface {
-		Marshal(x, y *big.Int) []byte
-	}
-
-	if curve, ok := pub.Curve.(marshaller); ok {
+	if curve, ok := pub.Curve.(crypto.BetterCurve); ok {
 		Rb := curve.Marshal(R.PublicKey.X, R.PublicKey.Y)
 		ct = make([]byte, len(Rb)+len(em)+len(d))
 		copy(ct, Rb)
@@ -305,10 +303,7 @@ func (prv *PrivateKey) Decrypt(c, s1, s2 []byte) (m []byte, err error) {
 	R := new(PublicKey)
 	R.Curve = prv.PublicKey.Curve
 
-	type unmarshaler interface {
-		Unmarshal([]byte) (x, y *big.Int)
-	}
-	if curve, ok := R.Curve.(unmarshaler); ok {
+	if curve, ok := R.Curve.(crypto.BetterCurve); ok {
 		R.X, R.Y = curve.Unmarshal(c[:rLen])
 		if R.X == nil {
 			return nil, ErrInvalidPublicKey
diff --git a/crypto/signature_cgo.go b/crypto/signature_cgo.go
index 835bbf717d..dd187f142d 100644
--- a/crypto/signature_cgo.go
+++ b/crypto/signature_cgo.go
@@ -21,8 +21,10 @@ package crypto
 
 import (
 	"crypto/ecdsa"
+	"crypto/elliptic"
 	"errors"
 	"fmt"
+	"math/big"
 
 	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/ethereum/go-ethereum/crypto/secp256k1"
@@ -80,7 +82,15 @@ func CompressPubkey(pubkey *ecdsa.PublicKey) []byte {
 	return secp256k1.CompressPubkey(pubkey.X, pubkey.Y)
 }
 
+// BetterCurve is an interface that combines both a curve
+// and (un)-marshalling functions to and from that curve.
+type BetterCurve interface {
+	elliptic.Curve
+	Marshal(x, y *big.Int) []byte
+	Unmarshal(data []byte) (x, y *big.Int)
+}
+
 // S256 returns an instance of the secp256k1 curve.
-func S256() *secp256k1.BitCurve {
+func S256() BetterCurve {
 	return secp256k1.S256()
 }
diff --git a/p2p/rlpx/rlpx.go b/p2p/rlpx/rlpx.go
index 2d38834f4d..d34ef60d50 100644
--- a/p2p/rlpx/rlpx.go
+++ b/p2p/rlpx/rlpx.go
@@ -29,7 +29,6 @@ import (
 	"fmt"
 	"hash"
 	"io"
-	"math/big"
 	mrand "math/rand"
 	"net"
 	"time"
@@ -664,10 +663,7 @@ func exportPubkey(pub *ecies.PublicKey) []byte {
 	if pub == nil {
 		panic("nil pubkey")
 	}
-	type marshaller interface {
-		Marshal(x, y *big.Int) []byte
-	}
-	if curve, ok := pub.Curve.(marshaller); ok {
+	if curve, ok := pub.Curve.(crypto.BetterCurve); ok {
 		return curve.Marshal(pub.X, pub.Y)[1:]
 	}
 	return []byte{}