下面的类实现了文件的加密和解密操作，试验了几种文件类型均没有问题，现在和大家共享一下。
namespace MyCryptoHelp
{
/// <summary>
/// 异常处理类
/// </summary>
public class CryptoHelpException : ApplicationException
{
public CryptoHelpException(string msg):base(msg){}
}
/// <summary>
/// CryptHelp
/// </summary>
public class CryptoHelp
{
private const ulong FC_TAG = 0xFC010203040506CF;
private const int BUFFER_SIZE = 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="password">加密密码</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
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 = CryptoHelp.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();
}
}
}
/// <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="password">解密密码</param>
public static void DecryptFile(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 = CryptoHelp.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 CryptoHelpException("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 CryptoHelpException("文件被破坏");
}
if(outValue != lSize)
throw new CryptoHelpException("文件大小不匹配");
}
}
}
}
// 调用
public class TestClass
{
string myPassword = "TEST_PASSWORD_~!@#";
string myPlainFile = "test.txt";
string myEncryptedFile = "test.encrypted";
string myDecryptedFile = "test.decrypted";
[STAThread]
static void Main()
{
CryptoHelp.EncryptFile(myPlainFile, myEncryptedFile, myPassword);
CryptoHelp.DecryptFile(myEncryptedFile,myDecryptedFile, myPassword);
}
}
