const BlockSize = 16
var IV = make([]byte, BlockSize)
func GCMDecrypt(K, IV, C, A []byte) (P, _T []byte)
func GCMEncrypt(K, IV, P, A []byte) (C, T []byte)
func GHASH(H []byte, A []byte, C []byte) (X []byte)
func GetH(key []byte) (H []byte)
func GetY0(H, IV []byte) []byte
func MSB(len int, S []byte) (out []byte)
func NewCipher(key []byte) (cipher.Block, error)
NewCipher creates and returns a new cipher.Block.
func Rightshift(V []byte)
func SetIV(iv []byte) error
func Sm4CFB(key []byte, in []byte, mode bool) (out []byte, err error)
密码反馈模式（Cipher FeedBack (CFB)） https://blog.csdn.net/zy_strive_2012/article/details/102520356 https://blog.csdn.net/sinat_23338865/article/details/72869841
func Sm4Cbc(key []byte, in []byte, mode bool) (out []byte, err error)
func Sm4Ecb(key []byte, in []byte, mode bool) (out []byte, err error)
func Sm4GCM(key []byte, IV, in, A []byte, mode bool) ([]byte, []byte, error)
Paper: The Galois/Counter Mode of Operation (GCM) David A. Mcgrew，John Viega .2004.
func Sm4OFB(key []byte, in []byte, mode bool) (out []byte, err error)
输出反馈模式（Output feedback, OFB） https://blog.csdn.net/chengqiuming/article/details/82390910 https://blog.csdn.net/sinat_23338865/article/details/72869841
func WriteKeyToPem(key SM4Key, pwd []byte) ([]byte, error)
WriteKeyToPem will convert SM4Key to PEM format data and return it.
func WriteKeyToPemFile(FileName string, key SM4Key, pwd []byte) error
WriteKeyToPemFile will convert SM4Key to PEM format data, then write it into the input filename.
type SM4Key []byte
func ReadKeyFromPem(data []byte, pwd []byte) (SM4Key, error)
ReadKeyFromPem will return SM4Key from PEM format data.
func ReadKeyFromPemFile(FileName string, pwd []byte) (SM4Key, error)
ReadKeyFromPemFile will return SM4Key from filename that saved PEM format data.
Cipher is an instance of SM4 encryption.
type Sm4Cipher struct {
// contains filtered or unexported fields
}
func (c *Sm4Cipher) BlockSize() int
func (c *Sm4Cipher) Decrypt(dst, src []byte)
func (c *Sm4Cipher) Encrypt(dst, src []byte)