国密SM4——golang的实现_golang sm4

SM4算法是我国商用密码标准，其前身是SMS4算法。SM4算法是一个分组加密算法，分组长度和密钥长度均128bit。SM4算法使用32轮的非线性迭代结构。SM4在最后一轮非线性迭代之后加上了一个反序变换，因此SM4中只要解密密钥是加密密钥的逆序，它的解密算法与加密算法就可以保持一致。SM4的主体运算是非平衡Feistel网络。

整体逻辑结构如图所示，经过32轮变换把明文变换为密文。

SM4算法类似于国际密码算法AES。

代码示例： 

1. CBC分组模式（Cipher Block Chaining ，密码分组链模式）

package main
 
import (
	"bytes"
	"crypto/cipher"
	"encoding/base64"
	"fmt"
	"github.com/tjfoc/gmsm/sm4"
	"log"
)
 
func main() {
	SM4()
}
func SM4() {
	// 128比特密钥
	key := []byte("1234567890abcdef")
	// 128比特iv
	iv := make([]byte, sm4.BlockSize)
	data := []byte("hello 国密SM4")
	fmt.Println("SM4加密密文是：", string(data))
	ciphertxt, err := sm4Encrypt(key, iv, data)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("SM4加密结果: %x\n", ciphertxt)
	fmt.Println("SM4加密结果:\n", base64.StdEncoding.EncodeToString(ciphertxt))
 
	res, err := sm4Decrypt(key, iv, ciphertxt)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("SM4解密密文是：", string(res))
}
func sm4Encrypt(key, iv, plainText []byte) ([]byte, error) {
	block, err := sm4.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockSize := block.BlockSize()
	origData := pkcs5Padding(plainText, blockSize)
	blockMode := cipher.NewCBCEncrypter(block, iv)
	cryted := make([]byte, len(origData))
	blockMode.CryptBlocks(cryted, origData)
	return cryted, nil
}
 
func sm4Decrypt(key, iv, cipherText []byte) ([]byte, error) {
	block, err := sm4.NewCipher(key)
	if err != nil {
		return nil, err
	}
	blockMode := cipher.NewCBCDecrypter(block, iv)
	origData := make([]byte, len(cipherText))
	blockMode.CryptBlocks(origData, cipherText)
	origData = pkcs5UnPadding(origData)
	return origData, nil
}
 
// pkcs5填充
func pkcs5Padding(src []byte, blockSize int) []byte {
	padding := blockSize - len(src)%blockSize
	padtext := bytes.Repeat([]byte{byte(padding)}, padding)
	return append(src, padtext...)
}
 
func pkcs5UnPadding(src []byte) []byte {
	length := len(src)
	if length == 0 {
		return nil
	}
	unpadding := int(src[length-1])
	return src[:(length - unpadding)]
}

2.CFB分组模式（Cipher FeedBack ，密码反馈模式）：

package main
 
import (
	"crypto/cipher"
	"crypto/rand"
	"fmt"
	"github.com/tjfoc/gmsm/sm4"
	"io"
)
 
func main() {
	key := []byte("1234567890abcdef")
	iv, encrypt, err := Sm4EncryptCfb([]byte("hello 江洲"), key)
	fmt.Printf("iv:%X,encrpyt:%X,err:%v\n", iv, encrypt, err)
	plainData, err := Sm4DecryptCfb(encrypt, key, iv)
	fmt.Printf("解密数据：%s,err:%v", plainData, err)
 
}
 
// Sm4EncryptCfb sm4加密，CFB模式
//goland:noinspection GoNameStartsWithPackageName
func Sm4EncryptCfb(plainData, key []byte) (iv, encryptData []byte, err error) {
	block, err := sm4.NewCipher(key)
	if err != nil {
		return nil, nil, err
	}
	encryptData = make([]byte, len(plainData))
	iv = make([]byte, sm4.BlockSize)
	fmt.Println("iv:", iv)
	if _, err = io.ReadFull(rand.Reader, iv); err != nil {
		return nil, nil, err
	}
	mode := cipher.NewCFBEncrypter(block, iv)
	mode.XORKeyStream(encryptData, plainData)
	fmt.Println("iv", iv)
	return
}
 
// Sm4DecryptCfb sm4解密，CFB模式
//goland:noinspection GoNameStartsWithPackageName
func Sm4DecryptCfb(encryptData, key, iv []byte) (plainData []byte, err error) {
	block, err := sm4.NewCipher(key)
	if err != nil {
		return nil, err
	}
	plainData = make([]byte, len(encryptData))
	mode := cipher.NewCFBDecrypter(block, iv)
	mode.XORKeyStream(plainData, encryptData)
	return
}

3.OFB分组模式(Output FeedBack，输出反馈模式)

package main
 
import (
	"crypto/cipher"
	"crypto/rand"
	"fmt"
	"github.com/tjfoc/gmsm/sm4"
	"io"
)
 
func main() {
	key := []byte("1234567890abcdef")
	iv, encryptData, err := Sm4EncryptOfb([]byte("hello 江洲"), key)
	fmt.Printf("iv:%X,encrpyt:%X,err:%v\n", iv, encryptData, err)
	plainData, err := Sm4DecryptOfb(encryptData, key, iv)
	fmt.Println("加密的数据为：", string(plainData))
}
 
// Sm4EncryptOfb sm4加密，OFB模式
//goland:noinspection GoNameStartsWithPackageName
func Sm4EncryptOfb(plainData, key []byte) (iv, encryptData []byte, err error) {
	block, err := sm4.NewCipher(key)
	if err != nil {
		return nil, nil, err
	}
	encryptData = make([]byte, len(plainData))
	iv = make([]byte, sm4.BlockSize)
	if _, err = io.ReadFull(rand.Reader, iv); err != nil {
		return nil, nil, err
	}
	mode := cipher.NewOFB(block, iv)
	mode.XORKeyStream(encryptData, plainData)
	return
}
 
// Sm4DecryptOfb sm4解密，OFB模式
//goland:noinspection GoNameStartsWithPackageName
func Sm4DecryptOfb(encryptData, key, iv []byte) (plainData []byte, err error) {
	block, err := sm4.NewCipher(key)
	if err != nil {
		return nil, err
	}
	plainData = make([]byte, len(encryptData))
	mode := cipher.NewOFB(block, iv)
	mode.XORKeyStream(plainData, encryptData)
	return
}

以上代码中，SM4用到的库为：github.com/tjfoc/gmsm