国密算法（SM4）在C#里面的简单封装

前言

基础需要第三方Nuget包：Portable.BouncyCastle；
添加方法：右击项目名称，选择“管理Nuget程序包”，在搜索栏搜索Portable.BouncyCastle，选择安装。

---

一、SM4是什么？

SM4是一种分组密码算法，由我国国家密码管理局在2012年发布，常用于无线互联网加密等领域。SM4是一种分组密码算法，其分组长度为128位（即16字节，4字），密钥长度也为128位（即16字节，4字）。其加解密过程采用了32轮迭代机制（与DES、AES类似），每一轮需要一个轮密钥（与DES、AES类似）。

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二、使用步骤

1.引入库

using Org.BouncyCastle.Utilities.Encoders;

2.读入数据

代码如下（示例）：

/// 

/// SM4工具类
/// 
public class SM4Util
{
    public string secretKey = "1884546261730461"; // 长度必须为16字节
    public string iv = "0000000000000000";
    public bool hexString = false;

    public string Encrypt_ECB(string plainText)
    {
        var ctx = new SM4_Context
        {
            isPadding = true,
            mode = SM4.SM4_ENCRYPT
        };

        byte[] keyBytes;
        if (hexString)
        {
            keyBytes = Hex.Decode(secretKey);
        }
        else
        {
            keyBytes = Encoding.ASCII.GetBytes(secretKey);
        }

        var sm4 = new SM4();
        sm4.Sm4_setkey_enc(ctx, keyBytes);
        byte[] encrypted = sm4.Sm4_crypt_ecb(ctx, Encoding.ASCII.GetBytes(plainText));

        string cipherText = Encoding.ASCII.GetString(Hex.Encode(encrypted));
        return cipherText;
    }

    public byte[] Encrypt_ECB(byte[] plainBytes, byte[] keyBytes)
    {
        var ctx = new SM4_Context
        {
            isPadding = false,
            mode = SM4.SM4_ENCRYPT
        };

        var sm4 = new SM4();
        sm4.Sm4_setkey_enc(ctx, keyBytes);
        byte[] encrypted = sm4.Sm4_crypt_ecb(ctx, plainBytes);
        return encrypted;

        //return Hex.Encode(encrypted);
    }

    public string Decrypt_ECB(string cipherText)
    {
        var ctx = new SM4_Context
        {
            isPadding = true,
            mode = SM4.SM4_DECRYPT
        };

        byte[] keyBytes;
        if (hexString)
        {
            keyBytes = Hex.Decode(secretKey);
        }
        else
        {
            keyBytes = Encoding.ASCII.GetBytes(secretKey);
        }

        var sm4 = new SM4();
        sm4.Sm4_setkey_dec(ctx, keyBytes);
        byte[] decrypted = sm4.Sm4_crypt_ecb(ctx, Hex.Decode(cipherText));
        return Encoding.ASCII.GetString(decrypted);
    }

    public string Encrypt_CBC(string plainText)
    {
        var ctx = new SM4_Context
        {
            isPadding = true,
            mode = SM4.SM4_ENCRYPT
        };

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

        var sm4 = new SM4();
        sm4.Sm4_setkey_enc(ctx, keyBytes);
        byte[] encrypted = sm4.Sm4_crypt_cbc(ctx, ivBytes, Encoding.ASCII.GetBytes(plainText));

        string cipherText = Encoding.ASCII.GetString(Hex.Encode(encrypted));
        return cipherText;
    }

    public string Decrypt_CBC(string cipherText)
    {
        var ctx = new SM4_Context
        {
            isPadding = true,
            mode = SM4.SM4_DECRYPT
        };

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

        var sm4 = new SM4();
        sm4.Sm4_setkey_dec(ctx, keyBytes);
        byte[] decrypted = sm4.Sm4_crypt_cbc(ctx, ivBytes, Hex.Decode(cipherText));
        return Encoding.ASCII.GetString(decrypted);
    }
}

---

public class SM4
{
    public const int SM4_ENCRYPT = 1;
    public const int SM4_DECRYPT = 0;

    private static 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) | b[i + 3] & 0xff & 0xffffffffL;
        return n;
    }

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

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

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

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

        byte[] ret;
        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(SM4_Context ctx, byte[] key)
    {
        ctx.mode = SM4_ENCRYPT;
        Sm4_setkey(ctx.sk, key);
    }

    public void Sm4_setkey_dec(SM4_Context ctx, byte[] key)
    {
        ctx.mode = SM4_DECRYPT;
        Sm4_setkey(ctx.sk, key);
        int i;
        for (i = 0; i < 16; i++)
        {
            SWAP(ctx.sk, i);
        }
    }

    public byte[] Sm4_crypt_ecb(SM4_Context 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(SM4_Context 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);
        var 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, i * 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, i * 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)
        {
            byte[] bous = Padding(bousList.ToArray(), SM4_DECRYPT);
            return bous;
        }
        else
        {
            return bousList.ToArray();
        }
    }
}

public class SM4_Context
{
    public int mode;

    public long[] sk;

    public bool isPadding;

    public SM4_Context()
    {
        this.mode = 1;
        this.isPadding = true;
        this.sk = new long[32];
    }
}