Merge pull request #6 from ecies/kem-suffix-remove

Kem suffix remove

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
 	}

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
 	}

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")
 	}
@@ -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())
 }

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")
 	}
@@ -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())
 }

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
+}