From dd154f424097564271a29ce8c683ed35b8e6ca89 Mon Sep 17 00:00:00 2001
From: L11R <savely@krasovsky.me>
Date: Fri, 16 Aug 2019 11:22:31 +0300
Subject: [PATCH 1/2] zero padding extracted into dedicated func

---
 privatekey.go | 11 ++---------
 publickey.go  | 11 ++---------
 utils.go      |  8 ++++++++
 3 files changed, 12 insertions(+), 18 deletions(-)

diff --git a/privatekey.go b/privatekey.go
index 0610d7b..9366ce8 100644
--- a/privatekey.go
+++ b/privatekey.go
@@ -86,15 +86,8 @@ func (k *PrivateKey) EncapsulateKEM(pub *PublicKey) ([]byte, error) {
 
 	// Sometimes shared secret coordinates are less than 32 bytes; Big Endian
 	l := len(pub.Curve.Params().P.Bytes())
-	for i := 0; i < l-len(sx.Bytes()); i++ {
-		secret.Write([]byte{0x00})
-	}
-	secret.Write(sx.Bytes())
-
-	for i := 0; i < l-len(sy.Bytes()); i++ {
-		secret.Write([]byte{0x00})
-	}
-	secret.Write(sy.Bytes())
+	secret.Write(zeroPad(sx.Bytes(), l))
+	secret.Write(zeroPad(sy.Bytes(), l))
 
 	return kdf(secret.Bytes())
 }
diff --git a/publickey.go b/publickey.go
index 6c37774..72469ca 100644
--- a/publickey.go
+++ b/publickey.go
@@ -148,15 +148,8 @@ func (k *PublicKey) DecapsulateKEM(priv *PrivateKey) ([]byte, error) {
 
 	// Sometimes shared secret coordinates are less than 32 bytes; Big Endian
 	l := len(priv.Curve.Params().P.Bytes())
-	for i := 0; i < l-len(sx.Bytes()); i++ {
-		secret.Write([]byte{0x00})
-	}
-	secret.Write(sx.Bytes())
-
-	for i := 0; i < l-len(sy.Bytes()); i++ {
-		secret.Write([]byte{0x00})
-	}
-	secret.Write(sy.Bytes())
+	secret.Write(zeroPad(sx.Bytes(), l))
+	secret.Write(zeroPad(sy.Bytes(), l))
 
 	return kdf(secret.Bytes())
 }
diff --git a/utils.go b/utils.go
index 063696e..e25af85 100644
--- a/utils.go
+++ b/utils.go
@@ -16,3 +16,11 @@ func kdf(secret []byte) (key []byte, err error) {
 
 	return key, nil
 }
+
+func zeroPad(b []byte, leigth int) []byte {
+	for i := 0; i < leigth-len(b); i++ {
+		b = append([]byte{0x00}, b...)
+	}
+
+	return b
+}

From 9e79fb5e8407927234071ae5963f787cdda609e6 Mon Sep 17 00:00:00 2001
From: L11R <savely@krasovsky.me>
Date: Fri, 16 Aug 2019 11:36:33 +0300
Subject: [PATCH 2/2] code style fix

---
 ecies.go      | 4 ++--
 ecies_test.go | 4 ++--
 privatekey.go | 4 ++--
 publickey.go  | 4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/ecies.go b/ecies.go
index 24bfd86..44e646d 100644
--- a/ecies.go
+++ b/ecies.go
@@ -23,7 +23,7 @@ func Encrypt(pubkey *PublicKey, msg []byte) ([]byte, error) {
 	ct.Write(ek.PublicKey.Bytes(false))
 
 	// Derive shared secret
-	ss, err := ek.EncapsulateKEM(pubkey)
+	ss, err := ek.Encapsulate(pubkey)
 	if err != nil {
 		return nil, err
 	}
@@ -74,7 +74,7 @@ func Decrypt(privkey *PrivateKey, msg []byte) ([]byte, error) {
 	msg = msg[65:]
 
 	// Derive shared secret
-	ss, err := ethPubkey.DecapsulateKEM(privkey)
+	ss, err := ethPubkey.Decapsulate(privkey)
 	if err != nil {
 		return nil, err
 	}
diff --git a/ecies_test.go b/ecies_test.go
index 7c86333..80f04ad 100644
--- a/ecies_test.go
+++ b/ecies_test.go
@@ -74,11 +74,11 @@ func TestKEM(t *testing.T) {
 	k1 := NewPrivateKeyFromBytes(new(big.Int).SetInt64(2).Bytes())
 	k2 := NewPrivateKeyFromBytes(new(big.Int).SetInt64(3).Bytes())
 
-	sk1, err := k1.EncapsulateKEM(k2.PublicKey)
+	sk1, err := k1.Encapsulate(k2.PublicKey)
 	if !assert.NoError(t, err) {
 		return
 	}
-	sk2, err := k1.PublicKey.DecapsulateKEM(k2)
+	sk2, err := k1.PublicKey.Decapsulate(k2)
 	if !assert.NoError(t, err) {
 		return
 	}
diff --git a/privatekey.go b/privatekey.go
index 9366ce8..47dffbb 100644
--- a/privatekey.go
+++ b/privatekey.go
@@ -71,9 +71,9 @@ func (k *PrivateKey) Hex() string {
 	return hex.EncodeToString(k.Bytes())
 }
 
-// EncapsulateKEM encapsulates key by using Key Encapsulation Mechanism and returns symmetric key;
+// Encapsulate encapsulates key by using Key Encapsulation Mechanism and returns symmetric key;
 // can be safely used as encryption key
-func (k *PrivateKey) EncapsulateKEM(pub *PublicKey) ([]byte, error) {
+func (k *PrivateKey) Encapsulate(pub *PublicKey) ([]byte, error) {
 	if pub == nil {
 		return nil, errors.New("public key is empty")
 	}
diff --git a/publickey.go b/publickey.go
index 72469ca..b193b15 100644
--- a/publickey.go
+++ b/publickey.go
@@ -133,9 +133,9 @@ func (k *PublicKey) Hex(compressed bool) string {
 	return hex.EncodeToString(k.Bytes(compressed))
 }
 
-// DecapsulateKEM decapsulates key by using Key Encapsulation Mechanism and returns symmetric key;
+// Decapsulate decapsulates key by using Key Encapsulation Mechanism and returns symmetric key;
 // can be safely used as encryption key
-func (k *PublicKey) DecapsulateKEM(priv *PrivateKey) ([]byte, error) {
+func (k *PublicKey) Decapsulate(priv *PrivateKey) ([]byte, error) {
 	if priv == nil {
 		return nil, errors.New("public key is empty")
 	}