上一次咱们说到了文件的合并与拆分，今天给大家带来的是加解密。这次的内容可以说是得结合上次的文件合并与拆分来做，为什么呢？大家应该都知道，加解密只能对文件或字符串来操作，如果想对整个文件夹加密该怎么办呢，我想大家应该都能想到把文件夹所有文件合并成一个文件。这样很多人应该都会想到对文件夹进行压缩。这个方法我也试过。但当我的文件超过4G的时候就会出现问题。所以，我就改用了文件的合并与拆分来替换解压缩。好了，接下来说说加解密。
加解密的时候也是用流来操作文件。如果是大文件，同样也会出现内存溢出的情况，我们解决的方法依然是分段循环来进行读写。
接下来，我还是把代码贴出来大家试试：
public class CryptoHelp
{
private const ulong FcTag = 0xFC010203040506CF;
private const int BufferSize = 128 * 1024;
/// <summary>
/// 检验两个Byte数组是否相同
/// </summary>
/// <param name="b1">Byte数组</param>
/// <param name="b2">Byte数组</param>
/// <returns>true－相等</returns>
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;
}
/// <summary>
/// 创建Rijndael SymmetricAlgorithm
/// </summary>
/// <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;
}
/// <summary>
/// 加密文件随机数生成
/// </summary>
private static RandomNumberGenerator rand = new RNGCryptoServiceProvider();
/// <summary>
/// 生成指定长度的随机Byte数组
/// </summary>
/// <param name="count">Byte数组长度</param>
/// <returns>随机Byte数组</returns>
private static byte[] GenerateRandomBytes(int count)
{
byte[] bytes = new byte[count];
rand.GetBytes(bytes);
return bytes;
}
/// <summary>
/// 加密文件
/// </summary>
/// <param name="inFile">待加密文件</param>
/// <param name="outFile">加密后输入文件</param>
/// <param name="userPassword">用户输入密码</param>
/// <param name="userId">用户ID</param>
public static void EncryptFile(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
byte[] bytes = new byte[BufferSize]; // 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(FcTag);
// 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();
}
}
}
/// <summary>
/// 解密文件
/// </summary>
/// <param name="inFile">待解密文件</param>
/// <param name="outFile">解密后输出文件</param>
/// <param name="userPassword">用户输入密码</param>
/// <returns>解密成功返回true，否则返回false</returns>
public static bool DecryptFile(string inFile, string outFile, string password)
{
// 创建打开文件流
using (FileStream fin = File.OpenRead(inFile),
fout = File.OpenWrite(outFile))
{
byte[] bytes = new byte[BufferSize];
int read = -1;
decimal value = 0;
decimal 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 (FcTag != tag)
{
MessageBox.Show(@"文件被破坏");
}
long numReads = lSize / BufferSize;
long slack = lSize % BufferSize;
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);
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)))
{
MessageBox.Show(@"文件被破坏");
}
}
if (outValue != lSize)
{
MessageBox.Show(@"文件大小不匹配");
}
}
return true;
}
}
调用：
加密：
CryptoHelp.EncryptFile(inPath, @"c:\encrypt.erar",
"12345678");//inPath打包后的文件路径
解密：
CryptoHelp.DecryptFile(inPath, @"c:\tmp.lock","12345678");//inPath要解密的文件路径,第二个参数为打包后的文件，接下来再调用一下文件的拆分方法，则可以把文件彻底还原回去
整个demo 下载地址s：https://files.cnblogs.com/cssmystyle/Encrypt.rar
