C#实现SM4国密加密

本文主要讲解“国密加密算法”SM系列之SM4的C#实现方法，加密规则请详阅国密局发布的文档。

首先需第三方Nuget包：Portable.BouncyCastle （源码来自http://www.bouncycastle.org/csharp/）

1.1 SM4主类

    /// <summary>
    /// 
    /// </summary>
    internal class SM4
    {
        /// <summary>
        /// 加密 非线性τ函数B=τ(A)
        /// </summary>
        /// <param name="b"></param>
        /// <param name="i"></param>
        /// <returns></returns>
        private static long GetULongByBe(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;
        }
        /// <summary>
        /// 解密 非线性τ函数B=τ(A)
        /// </summary>
        /// <param name="n"></param>
        /// <param name="b"></param>
        /// <param name="i"></param>
        private static void PutULongToBe(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);
        }

        /// <summary>
        /// 循环移位,为32位的x循环左移n位
        /// </summary>
        /// <param name="x"></param>
        /// <param name="n"></param>
        /// <returns></returns>
        private static long Rotl(long x, int n)
        {
            return ((x & 0xFFFFFFFF) << n) | x >> (32 - n);
        }

        /// <summary>
        /// 将密钥逆序
        /// </summary>
        /// <param name="sk"></param>
        /// <param name="i"></param>
        private static void Swap(long[] sk, int i)
        {
            long t = sk[i];
            sk[i] = sk[(31 - i)];
            sk[(31 - i)] = t;
        }
        /// <summary>
        /// S盒 
        /// </summary>
        public byte[] SboxTable = new byte[] {
         //   0     1     2     3     4     5     6     7     8     9     a     b     c     d     e     f
            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
        };

        /// <summary>
        /// 系统参数FK
        /// </summary>
        public uint[] FK = { 0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc };
        /// <summary>
        /// 固定参数CK
        /// </summary>
        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
        };

        /// <summary>
        /// Sm4的S盒取值
        /// </summary>
        /// <param name="inch"></param>
        /// <returns></returns>
        private byte Sm4Sbox(byte inch)
        {
            int i = inch & 0xFF;
            byte retVal = SboxTable[i];
            return retVal;
        }

        /// <summary>
        /// 线性变换 L
        /// </summary>
        /// <param name="ka"></param>
        /// <returns></returns>
        private long Sm4Lt(long ka)
        {
            byte[] a = new byte[4];
            byte[] b = new byte[4];
            PutULongToBe(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 = GetULongByBe(b, 0);
            long c = bb ^ Rotl(bb, 2) ^ Rotl(bb, 10) ^ Rotl(bb, 18) ^ Rotl(bb, 24);
            return c;
        }
        /// <summary>
        /// 轮函数 F
        /// </summary>
        /// <param name="x0"></param>
        /// <param name="x1"></param>
        /// <param name="x2"></param>
        /// <param name="x3"></param>
        /// <param name="rk"></param>
        /// <returns></returns>
        private long Sm4F(long x0, long x1, long x2, long x3, long rk)
        {
            return x0 ^ Sm4Lt(x1 ^ x2 ^ x3 ^ rk);
        }

        /// <summary>
        /// 轮密钥rk
        /// </summary>
        /// <param name="ka"></param>
        /// <returns></returns>
        private long Sm4CalciRk(long ka)
        {
            byte[] a = new byte[4];
            byte[] b = new byte[4];
            PutULongToBe(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 = GetULongByBe(b, 0);
            long rk = bb ^ Rotl(bb, 13) ^ Rotl(bb, 23);
            return rk;
        }

        /// <summary>
        /// 加密密钥
        /// </summary>
        /// <param name="SK"></param>
        /// <param name="key"></param>
        private void SetKey(long[] SK, byte[] key)
        {
            //加密密钥长度为 128 比特
            long[] MK = new long[4];
            int i = 0;
            MK[0] = GetULongByBe(key, 0);
            MK[1] = GetULongByBe(key, 4);
            MK[2] = GetULongByBe(key, 8);
            MK[3] = GetULongByBe(key, 12);

            long[] k = new long[36];
            //轮密钥生成方法
            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)];
            }
        }
        /// <summary>
        /// 解密函数
        /// </summary>
        /// <param name="sk">轮密钥</param>
        /// <param name="input">输入分组的密文</param>
        /// <param name="output">输出的对应的分组明文</param>
        private void Sm4OneRound(long[] sk, byte[] input, byte[] output)
        {
            int i = 0;
            long[] ulbuf = new long[36];
            ulbuf[0] = GetULongByBe(input, 0);
            ulbuf[1] = GetULongByBe(input, 4);
            ulbuf[2] = GetULongByBe(input, 8);
            ulbuf[3] = GetULongByBe(input, 12);
            while (i < 32) //开始32轮解密 ，一次进行4轮，共计八次
            {
                ulbuf[(i + 4)] = Sm4F(ulbuf[i], ulbuf[(i + 1)], ulbuf[(i + 2)], ulbuf[(i + 3)], sk[i]);
                i++;
            }
            PutULongToBe(ulbuf[35], output, 0);
            PutULongToBe(ulbuf[34], output, 4);
            PutULongToBe(ulbuf[33], output, 8);
            PutULongToBe(ulbuf[32], output, 12);
        }

        /// <summary>
        /// 补足 16 进制字符串的 0 字符，返回不带 0x 的16进制字符串
        /// </summary>
        /// <param name="input"></param>
        /// <param name="mode">1表示加密，0表示解密</param>
        /// <returns></returns>
        private static byte[] Padding(byte[] input, int mode)
        {
            if (input == null)
            {
                return null;
            }

            byte[] ret;
            if (mode == 1)
            {
                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[^1];
                ret = new byte[input.Length - p];
                Array.Copy(input, 0, ret, 0, input.Length - p);
            }
            return ret;
        }
        /// <summary>
        /// 设置加密的key
        /// </summary>
        /// <param name="ctx"></param>
        /// <param name="key"></param>
        public void SetKeyEnc(Sm4Context ctx, byte[] key)
        {
            ctx.Mode = 1;
            SetKey(ctx.Key, key);
        }
        /// <summary>
        /// 设置解密的key
        /// </summary>
        /// <param name="ctx"></param>
        /// <param name="key"></param>
        public void Sm4SetKeyDec(Sm4Context ctx, byte[] key)
        {
            ctx.Mode = 0;
            SetKey(ctx.Key, key);
            int i;
            for (i = 0; i < 16; i++)
            {
                Swap(ctx.Key, i);
            }
        }
        /// <summary>
        /// ECB
        /// </summary>
        /// <param name="ctx"></param>
        /// <param name="input"></param>
        /// <returns></returns>
        public byte[] Sm4CryptEcb(Sm4Context ctx, byte[] input)
        {
            if (ctx.IsPadding && (ctx.Mode == 1))
            {
                input = Padding(input, 1);
            }

            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);
                Sm4OneRound(ctx.Key, inBytes, outBytes);
                Array.Copy(outBytes, 0, bous, i * 16, length > 16 ? 16 : length);
            }

            if (ctx.IsPadding && ctx.Mode == 0)
            {
                bous = Padding(bous, 0);
            }
            return bous;
        }

        /// <summary>
        /// CBC
        /// </summary>
        /// <param name="ctx"></param>
        /// <param name="iv"></param>
        /// <param name="input"></param>
        /// <returns></returns>
        public byte[] Sm4CryptCbc(Sm4Context ctx, byte[] iv, byte[] input)
        {
            if (ctx.IsPadding && ctx.Mode == 1)
            {
                input = Padding(input, 1);
            }

            int length = input.Length;
            byte[] bins = new byte[length];
            Array.Copy(input, 0, bins, 0, length);
            List<byte> bousList = new List<byte>();

            int i;
            if (ctx.Mode == 1)
            {
                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]));
                    }
                    Sm4OneRound(ctx.Key, 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);
                    Sm4OneRound(ctx.Key, 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 == 0)
            {
                byte[] bous = Padding(bousList.ToArray(), 0);
                return bous;
            }
            else
            {
                return bousList.ToArray();
            }
        }
    }

1.2 SM4处理中心

    /// <summary>
    /// 
    /// </summary>
    internal class Sm4Context
    {
        public Sm4Context()
        {
            Mode = 1;
            IsPadding = true;
            Key = new long[32];
        }
        /// <summary>
        /// 1表示加密，0表示解密
        /// </summary>
        public int Mode;
        /// <summary>
        /// 密钥
        /// </summary>
        public long[] Key;
        /// <summary>
        /// 是否补足16进制字符串
        /// </summary>
        public bool IsPadding;
    }

1.3调用

    /// <summary>
    /// Sm4算法  
    /// 对标国际DES算法
    /// </summary>
    public class Sm4Crypto 
    {
        public Sm4Crypto()
        {
            Key = "98145489617106616498";
            Iv = "0000000000000000";
            HexString = false;
            CryptoMode = Sm4CryptoEnum.ECB;
        }
        /// <summary>
        /// 数据
        /// </summary>
        public string Data { get; set; }
        /// <summary>
        /// 秘钥
        /// </summary>
        public string Key { get; set; }
        /// <summary>
        /// 向量
        /// </summary>
        public string Iv { get; set; }
        /// <summary>
        /// 明文是否是十六进制
        /// </summary>
        public bool HexString { get; set; }
        /// <summary>
        /// 加密模式(默认ECB)
        /// </summary>
        public Sm4CryptoEnum CryptoMode { get; set; }

        #region 加密
        public string Encrypt(Sm4Crypto entity)
        {
            return entity.CryptoMode == Sm4CryptoEnum.CBC ? EncryptCBC(entity) : EncryptECB(entity);
        }
        /// <summary>
        /// ECB加密
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public static string EncryptECB(Sm4Crypto entity)
        {
            Sm4Context ctx = new Sm4Context
            {
                IsPadding = true
            };

            byte[] keyBytes = entity.HexString ? Hex.Decode(entity.Key) : Encoding.Default.GetBytes(entity.Key);

            SM4 sm4 = new SM4();
            sm4.SetKeyEnc(ctx, keyBytes);
            byte[] encrypted = sm4.Sm4CryptEcb(ctx, Encoding.Default.GetBytes(entity.Data));

            return Encoding.Default.GetString(Hex.Encode(encrypted));
        }
        /// <summary>
        /// CBC加密
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public static string EncryptCBC(Sm4Crypto entity)
        {
            Sm4Context ctx = new Sm4Context
            {
                IsPadding = true
            };

            byte[] keyBytes = entity.HexString ? Hex.Decode(entity.Key) : Encoding.Default.GetBytes(entity.Key);
            byte[] ivBytes = entity.HexString ? Hex.Decode(entity.Iv) : Encoding.Default.GetBytes(entity.Iv);

            SM4 sm4 = new SM4();
            sm4.SetKeyEnc(ctx, keyBytes);
            byte[] encrypted = sm4.Sm4CryptCbc(ctx, ivBytes, Encoding.Default.GetBytes(entity.Data));

            return encrypted.ToBase64();
        }
        #endregion


        #region 解密
        public object Decrypt(Sm4Crypto entity)
        {
            return entity.CryptoMode == Sm4CryptoEnum.CBC ? DecryptCBC(entity) : DecryptECB(entity);
        }
        /// <summary>
        ///  ECB解密
        /// </summary>
        /// <param name="entity"></param>
        /// <returns></returns>
        public static string DecryptECB(Sm4Crypto entity)
        {
            Sm4Context ctx = new Sm4Context
            {
                IsPadding = true,
                Mode = 0
            };

            byte[] keyBytes = entity.HexString ? Hex.Decode(entity.Key) : Encoding.Default.GetBytes(entity.Key);

            SM4 sm4 = new SM4();
            sm4.Sm4SetKeyDec(ctx, keyBytes);
            byte[] decrypted = sm4.Sm4CryptEcb(ctx, Hex.Decode(entity.Data));
            return Encoding.Default.GetString(decrypted);
        }
        /// <summary>
        /// CBC解密
        /// </summary>
        /// <param name="cipherText"></param>
        /// <returns></returns>
        public static string DecryptCBC(Sm4Crypto entity)
        {
            Sm4Context ctx = new Sm4Context
            {
                IsPadding = true,
                Mode = 0
            };

            byte[] keyBytes = entity.HexString ? Hex.Decode(entity.Key) : Encoding.Default.GetBytes(entity.Key);
            byte[] ivBytes = entity.HexString ? Hex.Decode(entity.Iv) : Encoding.Default.GetBytes(entity.Iv);

            SM4 sm4 = new SM4();
            sm4.Sm4SetKeyDec(ctx, keyBytes);
            byte[] decrypted = sm4.Sm4CryptCbc(ctx, ivBytes, Convert.FromBase64String(entity.Data));
            return Encoding.Default.GetString(decrypted);
        }
        #endregion

        /// <summary>
        /// 加密类型
        /// </summary>
        public enum Sm4CryptoEnum
        {
            /// <summary>
            /// ECB(电码本模式)
            /// </summary>
            [Description("ECB模式")]
            ECB = 0,
            /// <summary>
            /// CBC(密码分组链接模式)
            /// </summary>
            [Description("CBC模式")]
            CBC = 1
        }
    }

1.4 所有类涉及的引用

using Org.BouncyCastle.Utilities.Encoders;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Text;