SM4國產加密CBC演算法快速預覽與Framework4.5版本對接

郎中令發表於2024-07-03

針對日常加密演算法,大致分為對稱加密,非對稱加密,雜湊函式(MD5),其中對稱加密比較常見的,如AES、DES、3DES,對稱加密演算法是指加密和解密採用相同的金鑰口,是可逆的, 實習那會用的就是DES,網上很多現成的輪子。此外非對稱加密演算法, 常用的如 RSA演算法、‌ECC演算法、‌DSA等演算法, 非對稱不可逆,安全性更高,相對應加密效率稍微低一些, 國產加密如今崛起,SM系列中很多加密演算法,結合自身業務場景經過比較選取最優解SM4,本文用來記錄具體SM4的使用對接。

(測試版本Net6),直接 安裝BouncyCastle.Cryptography 包即可, 寫個幫助類,直接貼程式碼

        #region SM4解密解密

        public static void GenerateKeyHex(out string key, out string iv)
        {
            //用於生成對稱加密演算法
            var keyGenerator = new CipherKeyGenerator();
            keyGenerator.Init(new KeyGenerationParameters(new SecureRandom(), 128));
            var a = keyGenerator.GenerateKey();
            key = Hex.ToHexString(a);

            SecureRandom random = new SecureRandom();
            byte[] b = new byte[16]; // IV長度為16位元組
            random.NextBytes(b);
            iv = Hex.ToHexString(b);
        }

        //隨機生成金鑰
        public static string GetRandomIV() 
        {
            SecureRandom random = new();
            byte[] b = new byte[16]; // IV長度為16位元組
            random.NextBytes(b);
           return Hex.ToHexString(b);
        }



        //CBC模式加密
        public static byte[] CBCEncrypt(this string appkey)
        {
            byte[] plaintext = Encoding.UTF8.GetBytes(appkey);
            IBufferedCipher cipher = new PaddedBufferedBlockCipher(new CbcBlockCipher(new SM4Engine()), new Pkcs7Padding());
            cipher.Init(true, new ParametersWithIV(new KeyParameter(Decode(AppSetting.Secret.SMKey)), Decode(AppSetting.Secret.SMIV)));
            byte[] output = new byte[cipher.GetOutputSize(plaintext.Length)];
            int bytesProcessed = cipher.ProcessBytes(plaintext, 0, plaintext.Length, output, 0);
            cipher.DoFinal(output, bytesProcessed);
            return output;
        }

        //CBC模式解密
        public static byte[] CBCDecrypt(this string appkey)
        {
            try
            {
                byte[] ciphertext = Convert.FromBase64String(appkey);
                IBufferedCipher cipher = new PaddedBufferedBlockCipher(new CbcBlockCipher(new SM4Engine()), new Pkcs7Padding());
                cipher.Init(false, new ParametersWithIV(new KeyParameter(Decode(AppSetting.Secret.SMKey)), Decode(AppSetting.Secret.SMIV)));
                byte[] output = new byte[cipher.GetOutputSize(ciphertext.Length)];
                int bytesProcessed = cipher.ProcessBytes(ciphertext, 0, ciphertext.Length, output, 0);
                cipher.DoFinal(output, bytesProcessed);
                return RemovePadding(output);
            }
            catch
            {
                Comm.NLogHelper.WriteError($"登入校驗-解密失敗:{appkey}");
                return null;
            }


        }

        static byte[] Decode(string key)
        {
            return Regex.IsMatch(key, "^[0-9a-f]+$", RegexOptions.IgnoreCase) ? Hex.Decode(key) : Convert.FromBase64String(key);
        }

        // 去除填充字元
        public static byte[] RemovePadding(byte[] data)
        {
            int lastNonZeroByte = data.Length - 1;
            while (data[lastNonZeroByte] == 0)
            {
                lastNonZeroByte--;
            }
            // 擷取非零位元組之前的所有位元組
            byte[] result = new byte[lastNonZeroByte + 1];
            Array.Copy(data, result, lastNonZeroByte + 1);
            return result;
        }

        #endregion

其中金鑰和偏移量,可以根據上面生成的方法自行生成, 呼叫方法簡單

 
 //加密
 var encrypted = "加密欄位XXXXX".CBCEncrypt();
 string base64 = Convert.ToBase64String(encrypted);

 //解密
 var original =base64.CBCDecrypt();

但是對於老舊專案的低版本,比如FrameWork4.5 一下, 使用BouncyCastle.Crypto 包,所以需要手動書寫一下SM4 的幫助類, 程式碼如下,需要保證 密碼Key 和 偏移量 IV

        
        public const string CBCKey = "XXXX";
        public const string CBCIV = "xxxx";

        //CBC模式加密
        public static string EncryptCBC(string plainText, bool hexstring = true)
        {
            var ctx = new SM4Context();
            ctx.isPadding = true;
            ctx.mode = SM4CryptoServiceProvider.SM4_ENCRYPT;

            byte[] keyBytes;
            byte[] ivBytes;
            if (hexstring)
            {
                keyBytes = Hex.Decode(CBCKey);
                ivBytes = Hex.Decode(CBCIV);
            }
            else
            {
                keyBytes = Encoding.UTF8.GetBytes(CBCKey);
                ivBytes = Encoding.UTF8.GetBytes(CBCIV);
            }

            var sm4 = new SM4CryptoServiceProvider();
            sm4.sm4_setkey_enc(ctx, keyBytes);
            byte[] encrypted = sm4.sm4_crypt_cbc(ctx, ivBytes, Encoding.UTF8.GetBytes(plainText));

            string cipherText = Convert.ToBase64String(encrypted);
            return cipherText;
        }

        public string DecryptCBC(string cipherText)
        {
            var ctx = new SM4Context();
            ctx.isPadding = true;
            ctx.mode = SM4CryptoServiceProvider.SM4_DECRYPT;

            byte[] keyBytes;
            byte[] ivBytes;
            if (hexstring)
            {
                keyBytes = Hex.Decode(secretKey);
                ivBytes = Hex.Decode(iv);
            }
            else
            {
                keyBytes = Encoding.UTF8.GetBytes(secretKey);
                ivBytes = Encoding.UTF8.GetBytes(iv);
            }

            var sm4 = new SM4CryptoServiceProvider();
            sm4.sm4_setkey_dec(ctx, keyBytes);
            byte[] decrypted = sm4.sm4_crypt_cbc(ctx, ivBytes, Hex.Decode(cipherText));
            return Encoding.UTF8.GetString(decrypted);
        }

SM4Context 實現如下:

    internal class SM4Context
    {
        public int mode;

        public long[] sk;

        public bool isPadding;

        public SM4Context()
        {
            this.mode = 1;
            this.isPadding = true;
            this.sk = new long[32];
        }
    }

SM4CryptoServiceProvider 實現如下:

 internal class SM4CryptoServiceProvider
 {
     public const int SM4_ENCRYPT = 1;
     public const int SM4_DECRYPT = 0;

     private long GET_ULONG_BE(byte[] b, int i)
     {
         long n = (long)(b[i] & 0xff) << 24 | (long)((b[i + 1] & 0xff) << 16) | (long)((b[i + 2] & 0xff) << 8) | (long)(b[i + 3] & 0xff) & 0xffffffffL;
         return n;
     }

     private void PUT_ULONG_BE(long n, byte[] b, int i)
     {
         b[i] = (byte)(int)(0xFF & n >> 24);
         b[i + 1] = (byte)(int)(0xFF & n >> 16);
         b[i + 2] = (byte)(int)(0xFF & n >> 8);
         b[i + 3] = (byte)(int)(0xFF & n);
     }

     private long SHL(long x, int n)
     {
         return (x & 0xFFFFFFFF) << n;
     }

     private long ROTL(long x, int n)
     {
         return SHL(x, n) | x >> (32 - n);
     }

     private void SWAP(long[] sk, int i)
     {
         long t = sk[i];
         sk[i] = sk[(31 - i)];
         sk[(31 - i)] = t;
     }

     public byte[] SboxTable = new byte[] { (byte) 0xd6, (byte) 0x90, (byte) 0xe9, (byte) 0xfe,
         (byte) 0xcc, (byte) 0xe1, 0x3d, (byte) 0xb7, 0x16, (byte) 0xb6,
         0x14, (byte) 0xc2, 0x28, (byte) 0xfb, 0x2c, 0x05, 0x2b, 0x67,
         (byte) 0x9a, 0x76, 0x2a, (byte) 0xbe, 0x04, (byte) 0xc3,
         (byte) 0xaa, 0x44, 0x13, 0x26, 0x49, (byte) 0x86, 0x06,
         (byte) 0x99, (byte) 0x9c, 0x42, 0x50, (byte) 0xf4, (byte) 0x91,
         (byte) 0xef, (byte) 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43,
         (byte) 0xed, (byte) 0xcf, (byte) 0xac, 0x62, (byte) 0xe4,
         (byte) 0xb3, 0x1c, (byte) 0xa9, (byte) 0xc9, 0x08, (byte) 0xe8,
         (byte) 0x95, (byte) 0x80, (byte) 0xdf, (byte) 0x94, (byte) 0xfa,
         0x75, (byte) 0x8f, 0x3f, (byte) 0xa6, 0x47, 0x07, (byte) 0xa7,
         (byte) 0xfc, (byte) 0xf3, 0x73, 0x17, (byte) 0xba, (byte) 0x83,
         0x59, 0x3c, 0x19, (byte) 0xe6, (byte) 0x85, 0x4f, (byte) 0xa8,
         0x68, 0x6b, (byte) 0x81, (byte) 0xb2, 0x71, 0x64, (byte) 0xda,
         (byte) 0x8b, (byte) 0xf8, (byte) 0xeb, 0x0f, 0x4b, 0x70, 0x56,
         (byte) 0x9d, 0x35, 0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, (byte) 0xd1,
         (byte) 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, (byte) 0x87,
         (byte) 0xd4, 0x00, 0x46, 0x57, (byte) 0x9f, (byte) 0xd3, 0x27,
         0x52, 0x4c, 0x36, 0x02, (byte) 0xe7, (byte) 0xa0, (byte) 0xc4,
         (byte) 0xc8, (byte) 0x9e, (byte) 0xea, (byte) 0xbf, (byte) 0x8a,
         (byte) 0xd2, 0x40, (byte) 0xc7, 0x38, (byte) 0xb5, (byte) 0xa3,
         (byte) 0xf7, (byte) 0xf2, (byte) 0xce, (byte) 0xf9, 0x61, 0x15,
         (byte) 0xa1, (byte) 0xe0, (byte) 0xae, 0x5d, (byte) 0xa4,
         (byte) 0x9b, 0x34, 0x1a, 0x55, (byte) 0xad, (byte) 0x93, 0x32,
         0x30, (byte) 0xf5, (byte) 0x8c, (byte) 0xb1, (byte) 0xe3, 0x1d,
         (byte) 0xf6, (byte) 0xe2, 0x2e, (byte) 0x82, 0x66, (byte) 0xca,
         0x60, (byte) 0xc0, 0x29, 0x23, (byte) 0xab, 0x0d, 0x53, 0x4e, 0x6f,
         (byte) 0xd5, (byte) 0xdb, 0x37, 0x45, (byte) 0xde, (byte) 0xfd,
         (byte) 0x8e, 0x2f, 0x03, (byte) 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b,
         0x51, (byte) 0x8d, 0x1b, (byte) 0xaf, (byte) 0x92, (byte) 0xbb,
         (byte) 0xdd, (byte) 0xbc, 0x7f, 0x11, (byte) 0xd9, 0x5c, 0x41,
         0x1f, 0x10, 0x5a, (byte) 0xd8, 0x0a, (byte) 0xc1, 0x31,
         (byte) 0x88, (byte) 0xa5, (byte) 0xcd, 0x7b, (byte) 0xbd, 0x2d,
         0x74, (byte) 0xd0, 0x12, (byte) 0xb8, (byte) 0xe5, (byte) 0xb4,
         (byte) 0xb0, (byte) 0x89, 0x69, (byte) 0x97, 0x4a, 0x0c,
         (byte) 0x96, 0x77, 0x7e, 0x65, (byte) 0xb9, (byte) 0xf1, 0x09,
         (byte) 0xc5, 0x6e, (byte) 0xc6, (byte) 0x84, 0x18, (byte) 0xf0,
         0x7d, (byte) 0xec, 0x3a, (byte) 0xdc, 0x4d, 0x20, 0x79,
         (byte) 0xee, 0x5f, 0x3e, (byte) 0xd7, (byte) 0xcb, 0x39, 0x48 };

     public uint[] FK = { 0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc };

     public uint[] CK = { 0x00070e15,0x1c232a31,0x383f464d,0x545b6269,
                                     0x70777e85,0x8c939aa1,0xa8afb6bd,0xc4cbd2d9,
                                     0xe0e7eef5,0xfc030a11,0x181f262d,0x343b4249,
                                     0x50575e65,0x6c737a81,0x888f969d,0xa4abb2b9,
                                     0xc0c7ced5,0xdce3eaf1,0xf8ff060d,0x141b2229,
                                     0x30373e45,0x4c535a61,0x686f767d,0x848b9299,
                                     0xa0a7aeb5,0xbcc3cad1,0xd8dfe6ed,0xf4fb0209,
                                     0x10171e25,0x2c333a41,0x484f565d,0x646b7279 };

     private byte sm4Sbox(byte inch)
     {
         int i = inch & 0xFF;
         byte retVal = SboxTable[i];
         return retVal;
     }

     private long sm4Lt(long ka)
     {
         long bb = 0L;
         long c = 0L;
         byte[] a = new byte[4];
         byte[] b = new byte[4];
         PUT_ULONG_BE(ka, a, 0);
         b[0] = sm4Sbox(a[0]);
         b[1] = sm4Sbox(a[1]);
         b[2] = sm4Sbox(a[2]);
         b[3] = sm4Sbox(a[3]);
         bb = GET_ULONG_BE(b, 0);
         c = bb ^ ROTL(bb, 2) ^ ROTL(bb, 10) ^ ROTL(bb, 18) ^ ROTL(bb, 24);
         return c;
     }

     private long sm4F(long x0, long x1, long x2, long x3, long rk)
     {
         return x0 ^ sm4Lt(x1 ^ x2 ^ x3 ^ rk);
     }

     private long sm4CalciRK(long ka)
     {
         long bb = 0L;
         long rk = 0L;
         byte[] a = new byte[4];
         byte[] b = new byte[4];
         PUT_ULONG_BE(ka, a, 0);
         b[0] = sm4Sbox(a[0]);
         b[1] = sm4Sbox(a[1]);
         b[2] = sm4Sbox(a[2]);
         b[3] = sm4Sbox(a[3]);
         bb = GET_ULONG_BE(b, 0);
         rk = bb ^ ROTL(bb, 13) ^ ROTL(bb, 23);
         return rk;
     }

     private void sm4_setkey(long[] SK, byte[] key)
     {
         long[] MK = new long[4];
         long[] k = new long[36];
         int i = 0;
         MK[0] = GET_ULONG_BE(key, 0);
         MK[1] = GET_ULONG_BE(key, 4);
         MK[2] = GET_ULONG_BE(key, 8);
         MK[3] = GET_ULONG_BE(key, 12);
         k[0] = MK[0] ^ (long)FK[0];
         k[1] = MK[1] ^ (long)FK[1];
         k[2] = MK[2] ^ (long)FK[2];
         k[3] = MK[3] ^ (long)FK[3];
         for (; i < 32; i++)
         {
             k[(i + 4)] = (k[i] ^ sm4CalciRK(k[(i + 1)] ^ k[(i + 2)] ^ k[(i + 3)] ^ (long)CK[i]));
             SK[i] = k[(i + 4)];
         }
     }

     private void sm4_one_round(long[] sk, byte[] input, byte[] output)
     {
         int i = 0;
         long[] ulbuf = new long[36];
         ulbuf[0] = GET_ULONG_BE(input, 0);
         ulbuf[1] = GET_ULONG_BE(input, 4);
         ulbuf[2] = GET_ULONG_BE(input, 8);
         ulbuf[3] = GET_ULONG_BE(input, 12);
         while (i < 32)
         {
             ulbuf[(i + 4)] = sm4F(ulbuf[i], ulbuf[(i + 1)], ulbuf[(i + 2)], ulbuf[(i + 3)], sk[i]);
             i++;
         }
         PUT_ULONG_BE(ulbuf[35], output, 0);
         PUT_ULONG_BE(ulbuf[34], output, 4);
         PUT_ULONG_BE(ulbuf[33], output, 8);
         PUT_ULONG_BE(ulbuf[32], output, 12);
     }

     private byte[] padding(byte[] input, int mode)
     {
         if (input == null)
         {
             return null;
         }

         byte[] ret = (byte[])null;
         if (mode == SM4_ENCRYPT)
         {
             int p = 16 - input.Length % 16;
             ret = new byte[input.Length + p];
             Array.Copy(input, 0, ret, 0, input.Length);
             for (int i = 0; i < p; i++)
             {
                 ret[input.Length + i] = (byte)p;
             }
         }
         else
         {
             int p = input[input.Length - 1];
             ret = new byte[input.Length - p];
             Array.Copy(input, 0, ret, 0, input.Length - p);
         }
         return ret;
     }

     public void sm4_setkey_enc(SM4Context ctx, byte[] key)
     {
         ctx.mode = SM4_ENCRYPT;
         sm4_setkey(ctx.sk, key);
     }

     public void sm4_setkey_dec(SM4Context ctx, byte[] key)
     {
         int i = 0;
         ctx.mode = SM4_DECRYPT;
         sm4_setkey(ctx.sk, key);
         for (i = 0; i < 16; i++)
         {
             SWAP(ctx.sk, i);
         }
     }

     public byte[] sm4_crypt_ecb(SM4Context ctx, byte[] input)
     {
         if ((ctx.isPadding) && (ctx.mode == SM4_ENCRYPT))
         {
             input = padding(input, SM4_ENCRYPT);
         }

         int length = input.Length;
         byte[] bins = new byte[length];
         Array.Copy(input, 0, bins, 0, length);
         byte[] bous = new byte[length];
         for (int i = 0; length > 0; length -= 16, i++)
         {
             byte[] inBytes = new byte[16];
             byte[] outBytes = new byte[16];
             Array.Copy(bins, i * 16, inBytes, 0, length > 16 ? 16 : length);
             sm4_one_round(ctx.sk, inBytes, outBytes);
             Array.Copy(outBytes, 0, bous, i * 16, length > 16 ? 16 : length);
         }

         if (ctx.isPadding && ctx.mode == SM4_DECRYPT)
         {
             bous = padding(bous, SM4_DECRYPT);
         }
         return bous;
     }

     public byte[] sm4_crypt_cbc(SM4Context ctx, byte[] iv, byte[] input)
     {
         if (ctx.isPadding && ctx.mode == SM4_ENCRYPT)
         {
             input = padding(input, SM4_ENCRYPT);
         }

         int i = 0;
         int length = input.Length;
         byte[] bins = new byte[length];
         Array.Copy(input, 0, bins, 0, length);
         byte[] bous = null;
         List<byte> bousList = new List<byte>();
         if (ctx.mode == SM4_ENCRYPT)
         {
             for (int j = 0; length > 0; length -= 16, j++)
             {
                 byte[] inBytes = new byte[16];
                 byte[] outBytes = new byte[16];
                 byte[] out1 = new byte[16];

                 Array.Copy(bins, j * 16, inBytes, 0, length > 16 ? 16 : length);
                 for (i = 0; i < 16; i++)
                 {
                     outBytes[i] = ((byte)(inBytes[i] ^ iv[i]));
                 }
                 sm4_one_round(ctx.sk, outBytes, out1);
                 Array.Copy(out1, 0, iv, 0, 16);
                 for (int k = 0; k < 16; k++)
                 {
                     bousList.Add(out1[k]);
                 }
             }
         }
         else
         {
             byte[] temp = new byte[16];
             for (int j = 0; length > 0; length -= 16, j++)
             {
                 byte[] inBytes = new byte[16];
                 byte[] outBytes = new byte[16];
                 byte[] out1 = new byte[16];

                 Array.Copy(bins, j * 16, inBytes, 0, length > 16 ? 16 : length);
                 Array.Copy(inBytes, 0, temp, 0, 16);
                 sm4_one_round(ctx.sk, inBytes, outBytes);
                 for (i = 0; i < 16; i++)
                 {
                     out1[i] = ((byte)(outBytes[i] ^ iv[i]));
                 }
                 Array.Copy(temp, 0, iv, 0, 16);
                 for (int k = 0; k < 16; k++)
                 {
                     bousList.Add(out1[k]);
                 }
             }

         }

         if (ctx.isPadding && ctx.mode == SM4_DECRYPT)
         {
             bous = padding(bousList.ToArray(), SM4_DECRYPT);
             return bous;
         }
         else
         {
             return bousList.ToArray();
         }
     }
 }

如此大功告成, 兩邊可自行攻守,如果保證Key 和 IV一直,則能夠互通有無

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