c#使用SHA256算法实现对文件的加密和解密

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全栈工程师开发手册（作者：栾鹏）

c#教程全解

将当期目录的test.txt加密成文件test1.txt，再将加密后的test1.txt文件解密成test2.txt。

测试代码

static void Main(){    MyEncrypt.SHA_Encrypt("test.txt", "test1.txt", "123456");  //文件加密    MyEncrypt.SHA_Dencrypt("test1.txt", "test2.txt", "123456");  //文件解密}

加密解密工具类的实现

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Security.Cryptography;using System.IO;namespace util{    public class MyEncrypt    {        private const ulong FC_TAG = 0xFC010203040506CF;        private const int BUFFER_SIZE = 128 * 1024;        //检验两个Byte数组是否相同         private static bool CheckByteArrays(byte[] b1, byte[] b2)        {            if (b1.Length == b2.Length)            {                for (int i = 0; i < b1.Length; ++i)                {                    if (b1[i] != b2[i])                        return false;                }                return true;            }            return false;        }        /// <param name="password">密码</param>         /// <param name="salt"></param>         /// <returns>加密对象</returns>         private static SymmetricAlgorithm CreateRijndael(string password, byte[] salt)        {            PasswordDeriveBytes pdb = new PasswordDeriveBytes(password, salt, "SHA256", 1000);            SymmetricAlgorithm sma = Rijndael.Create();            sma.KeySize = 256;            sma.Key = pdb.GetBytes(32);            sma.Padding = PaddingMode.PKCS7;            return sma;        }        // 加密文件随机数生成         private static RandomNumberGenerator rand = new RNGCryptoServiceProvider();        // 生成指定长度的随机Byte数组         private static byte[] GenerateRandomBytes(int count)        {            byte[] bytes = new byte[count];            rand.GetBytes(bytes);            return bytes;        }        // 加密文件         public static void SHA_Encrypt(string inFile, string outFile, string password)        {            using (FileStream fin = File.OpenRead(inFile),            fout = File.OpenWrite(outFile))            {                long lSize = fin.Length; // 输入文件长度                 int size = (int)lSize;                byte[] bytes = new byte[BUFFER_SIZE]; // 缓存                 int read = -1; // 输入文件读取数量                 int value = 0;                // 获取IV和salt                 byte[] IV = GenerateRandomBytes(16);                byte[] salt = GenerateRandomBytes(16);                // 创建加密对象                 SymmetricAlgorithm sma = CreateRijndael(password, salt);                sma.IV = IV;                // 在输出文件开始部分写入IV和salt                 fout.Write(IV, 0, IV.Length);                fout.Write(salt, 0, salt.Length);                // 创建散列加密                 HashAlgorithm hasher = SHA256.Create();                using (CryptoStream cout = new CryptoStream(fout, sma.CreateEncryptor(), CryptoStreamMode.Write),                chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))                {                    BinaryWriter bw = new BinaryWriter(cout);                    bw.Write(lSize);                    bw.Write(FC_TAG);                    // 读写字节块到加密流缓冲区                     while ((read = fin.Read(bytes, 0, bytes.Length)) != 0)                    {                        cout.Write(bytes, 0, read);                        chash.Write(bytes, 0, read);                        value += read;                    }                    // 关闭加密流                     chash.Flush();                    chash.Close();                    // 读取散列                     byte[] hash = hasher.Hash;                    // 输入文件写入散列                     cout.Write(hash, 0, hash.Length);                    // 关闭文件流                     cout.Flush();                    cout.Close();                }            }        }        // 解密文件         public static void SHA_Dencrypt(string inFile, string outFile, string password)        {            // 创建打开文件流             using (FileStream fin = File.OpenRead(inFile),            fout = File.OpenWrite(outFile))            {                int size = (int)fin.Length;                byte[] bytes = new byte[BUFFER_SIZE];                int read = -1;                int value = 0;                int outValue = 0;                byte[] IV = new byte[16];                fin.Read(IV, 0, 16);                byte[] salt = new byte[16];                fin.Read(salt, 0, 16);                SymmetricAlgorithm sma = CreateRijndael(password, salt);                sma.IV = IV;                value = 32;                long lSize = -1;                // 创建散列对象, 校验文件                 HashAlgorithm hasher = SHA256.Create();                using (CryptoStream cin = new CryptoStream(fin, sma.CreateDecryptor(), CryptoStreamMode.Read),                chash = new CryptoStream(Stream.Null, hasher, CryptoStreamMode.Write))                {                    // 读取文件长度                     BinaryReader br = new BinaryReader(cin);                    lSize = br.ReadInt64();                    ulong tag = br.ReadUInt64();                    if (FC_TAG != tag)                        throw new Exception("文件被破坏");                    long numReads = lSize / BUFFER_SIZE;                    long slack = (long)lSize % BUFFER_SIZE;                    for (int i = 0; i < numReads; ++i)                    {                        read = cin.Read(bytes, 0, bytes.Length);                        fout.Write(bytes, 0, read);                        chash.Write(bytes, 0, read);                        value += read;                        outValue += read;                    }                    if (slack > 0)                    {                        read = cin.Read(bytes, 0, (int)slack);                        fout.Write(bytes, 0, read);                        chash.Write(bytes, 0, read);                        value += read;                        outValue += read;                    }                    chash.Flush();                    chash.Close();                    fout.Flush();                    fout.Close();                    byte[] curHash = hasher.Hash;                    // 获取比较和旧的散列对象                     byte[] oldHash = new byte[hasher.HashSize / 8];                    read = cin.Read(oldHash, 0, oldHash.Length);                    if ((oldHash.Length != read) || (!CheckByteArrays(oldHash, curHash)))                        throw new Exception("文件被破坏");                }                if (outValue != lSize)                    throw new Exception("文件大小不匹配");            }        }    } }

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