diff --git a/cipher.go b/cipher.go
index 2946c93..f8e67ef 100644
--- a/cipher.go
+++ b/cipher.go
@@ -1,9 +1,10 @@
 package pkcs8
 
 import (
-	"bytes"
 	"crypto/cipher"
 	"encoding/asn1"
+
+	"github.com/emmansun/gmsm/padding"
 )
 
 type cipherWithBlock struct {
@@ -43,18 +44,45 @@ func (c cipherWithBlock) Decrypt(key, iv, ciphertext []byte) ([]byte, error) {
 
 func cbcEncrypt(block cipher.Block, key, iv, plaintext []byte) ([]byte, error) {
 	mode := cipher.NewCBCEncrypter(block, iv)
-	paddingLen := block.BlockSize() - (len(plaintext) % block.BlockSize())
-	ciphertext := make([]byte, len(plaintext)+paddingLen)
-	copy(ciphertext, plaintext)
-	copy(ciphertext[len(plaintext):], bytes.Repeat([]byte{byte(paddingLen)}, paddingLen))
-	mode.CryptBlocks(ciphertext, ciphertext)
+	pkcs7 := padding.NewPKCS7Padding(uint(block.BlockSize()))
+	plainText := pkcs7.Pad(plaintext)
+	ciphertext := make([]byte, len(plainText))
+	mode.CryptBlocks(ciphertext, plainText)
 	return ciphertext, nil
 }
 
 func cbcDecrypt(block cipher.Block, key, iv, ciphertext []byte) ([]byte, error) {
 	mode := cipher.NewCBCDecrypter(block, iv)
+	pkcs7 := padding.NewPKCS7Padding(uint(block.BlockSize()))
 	plaintext := make([]byte, len(ciphertext))
 	mode.CryptBlocks(plaintext, ciphertext)
-	// TODO: remove padding
-	return plaintext, nil
+	return pkcs7.Unpad(plaintext)
+}
+
+type cipherWithGCM struct {
+	cipherWithBlock
+}
+
+func (c cipherWithGCM) Encrypt(key, iv, plaintext []byte) ([]byte, error) {
+	block, err := c.newBlock(key)
+	if err != nil {
+		return nil, err
+	}
+	aead, err := cipher.NewGCMWithNonceSize(block, len(iv))
+	if err != nil {
+		return nil, err
+	}
+	return aead.Seal(nil, iv, plaintext, nil), nil
+}
+
+func (c cipherWithGCM) Decrypt(key, iv, ciphertext []byte) ([]byte, error) {
+	block, err := c.newBlock(key)
+	if err != nil {
+		return nil, err
+	}
+	aead, err := cipher.NewGCMWithNonceSize(block, len(iv))
+	if err != nil {
+		return nil, err
+	}
+	return aead.Open(nil, iv, ciphertext, nil)
 }
diff --git a/cipher_aes.go b/cipher_aes.go
index c0372d1..734790f 100644
--- a/cipher_aes.go
+++ b/cipher_aes.go
@@ -44,11 +44,13 @@ var AES128CBC = cipherWithBlock{
 }
 
 // AES128GCM is the 128-bit key AES cipher in GCM mode.
-var AES128GCM = cipherWithBlock{
-	ivSize:   aes.BlockSize,
-	keySize:  16,
-	newBlock: aes.NewCipher,
-	oid:      oidAES128GCM,
+var AES128GCM = cipherWithGCM{
+	cipherWithBlock: cipherWithBlock{
+		ivSize:   12,
+		keySize:  16,
+		newBlock: aes.NewCipher,
+		oid:      oidAES128GCM,
+	},
 }
 
 // AES192CBC is the 192-bit key AES cipher in CBC mode.
@@ -60,11 +62,13 @@ var AES192CBC = cipherWithBlock{
 }
 
 // AES192GCM is the 912-bit key AES cipher in GCM mode.
-var AES192GCM = cipherWithBlock{
-	ivSize:   aes.BlockSize,
-	keySize:  24,
-	newBlock: aes.NewCipher,
-	oid:      oidAES192GCM,
+var AES192GCM = cipherWithGCM{
+	cipherWithBlock: cipherWithBlock{
+		ivSize:   12,
+		keySize:  24,
+		newBlock: aes.NewCipher,
+		oid:      oidAES192GCM,
+	},
 }
 
 // AES256CBC is the 256-bit key AES cipher in CBC mode.
@@ -76,9 +80,11 @@ var AES256CBC = cipherWithBlock{
 }
 
 // AES256GCM is the 256-bit key AES cipher in GCM mode.
-var AES256GCM = cipherWithBlock{
-	ivSize:   aes.BlockSize,
-	keySize:  32,
-	newBlock: aes.NewCipher,
-	oid:      oidAES256GCM,
+var AES256GCM = cipherWithGCM{
+	cipherWithBlock: cipherWithBlock{
+		ivSize:   12,
+		keySize:  32,
+		newBlock: aes.NewCipher,
+		oid:      oidAES256GCM,
+	},
 }
diff --git a/cipher_sm4.go b/cipher_sm4.go
index 89e480e..05d16e3 100644
--- a/cipher_sm4.go
+++ b/cipher_sm4.go
@@ -11,16 +11,13 @@ var (
 	oidSM4GCM = asn1.ObjectIdentifier{1, 2, 156, 10197, 1, 104, 8}
 )
 
-
 func init() {
 	RegisterCipher(oidSM4CBC, func() Cipher {
 		return SM4CBC
 	})
-	/* GCM mode usage is incorrect in this module
 	RegisterCipher(oidSM4GCM, func() Cipher {
 		return SM4GCM
 	})
-	*/
 }
 
 // SM4CBC is the 128-bit key SM4 cipher in CBC mode.
@@ -32,9 +29,11 @@ var SM4CBC = cipherWithBlock{
 }
 
 // SM4GCM is the 128-bit key SM4 cipher in GCM mode.
-var SM4GCM = cipherWithBlock{
-	ivSize:   sm4.BlockSize,
-	keySize:  16,
-	newBlock: sm4.NewCipher,
-	oid:      oidSM4GCM,
+var SM4GCM = cipherWithGCM{
+	cipherWithBlock: cipherWithBlock{
+		ivSize:   12,
+		keySize:  16,
+		newBlock: sm4.NewCipher,
+		oid:      oidSM4GCM,		
+	},
 }
diff --git a/pkcs8_test.go b/pkcs8_test.go
index 45f5548..7096c62 100644
--- a/pkcs8_test.go
+++ b/pkcs8_test.go
@@ -405,6 +405,15 @@ func TestMarshalPrivateKey(t *testing.T) {
 				},
 			},
 		},
+		{
+			password: []byte("password"),
+			opts: &pkcs8.Opts{
+				Cipher: pkcs8.SM4GCM,
+				KDFOpts: pkcs8.PBKDF2Opts{
+					SaltSize: 8, IterationCount: 2048, HMACHash: pkcs8.SM3,
+				},
+			},
+		},
 		{
 			password: []byte("password"),
 			opts: &pkcs8.Opts{