提供一個基於.NET的加密/解密算法

提供一個基於.NET SymmetricAlgorithm 類的、帶私鑰的加密/解密算法的包裝類。使用方法：
symmcrypto de = new SymmCrypto(SymmCrypto.SymmProvEnum.DES);
Response.Write(x.Decrypting(de.Encrypting("ok","yyy"),"yyy"));

類的實現c#編碼

using System;
using System.Security.Cryptography;
using System.IO;
using System.Text;

namespace eMeng
{
/// <summary>
/// SymmCrypto 的摘要說明。
/// SymmCrypto類實現.NET框架下的加密和解密服務。
/// 原作者： Frank Fang : [email protected]
/// </summary>
public class SymmCrypto
{
public enum SymmProvEnum : int
{
DES, RC2, Rijndael
}

private SymmetricAlgorithm mobjCryptoService;

/// <remarks>
/// 使用.Net SymmetricAlgorithm 類的構造器.
/// </remarks>
public SymmCrypto(SymmProvEnum NetSelected)
{
switch (NetSelected)
{
case SymmProvEnum.DES:
mobjCryptoService = new DESCryptoServiceProvider();
break;
case SymmProvEnum.RC2:
mobjCryptoService = new RC2CryptoServiceProvider();
break;
case SymmProvEnum.Rijndael:
mobjCryptoService = new RijndaelManaged();
break;
}
}

/// <remarks>
/// 使用自定義SymmetricAlgorithm類的構造器.
/// </remarks>
public SymmCrypto(SymmetricAlgorithm ServiceProvider)
{
mobjCryptoService = ServiceProvider;
}

/// <remarks>
/// Depending on the legal key size limitations of
/// a specific CryptoService provider and length of
/// the private key provided, padding the secret key
/// with space character to meet the legal size of the algorithm.
/// </remarks>
private byte[] GetLegalKey(string Key)
{
string sTemp;
if (mobjCryptoService.LegalKeySizes.Length > 0)
{
int lessSize = 0, moreSize = mobjCryptoService.LegalKeySizes[0].MinSize;
// key sizes are in bits
while (Key.Length * 8 > moreSize)
{
lessSize = moreSize;
moreSize += mobjCryptoService.LegalKeySizes[0].SkipSize;
}
sTemp = Key.PadRight(moreSize / 8, ' ');
}
else
sTemp = Key;

// convert the secret key to byte array
return ASCIIEncoding.ASCII.GetBytes(sTemp);
}

public string Encrypting(string Source, string Key)
{
byte[] bytIn = System.Text.ASCIIEncoding.ASCII.GetBytes(Source);
// create a MemoryStream so that the process can be done without I/O files
System.IO.MemoryStream ms = new System.IO.MemoryStream();

byte[] bytKey = GetLegalKey(Key);

// set the private key
mobjCryptoService.Key = bytKey;
mobjCryptoService.IV = bytKey;

// create an Encryptor from the Provider Service instance
ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();

// create Crypto Stream that transforms a stream using the encryption
CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);

// write out encrypted content into MemoryStream
cs.Write(bytIn, 0, bytIn.Length);
cs.FlushFinalBlock();

// get the output and trim the '/0' bytes
byte[] bytOut = ms.GetBuffer();
int i = 0;
for (i = 0; i < bytOut.Length; i++)
if (bytOut[i] == 0)
break;

// convert into Base64 so that the result can be used in xml
return System.Convert.ToBase64String(bytOut, 0, i);
}

public string Decrypting(string Source, string Key)
{
// convert from Base64 to binary
byte[] bytIn = System.Convert.FromBase64String(Source);
// create a MemoryStream with the input
System.IO.MemoryStream ms = new System.IO.MemoryStream(bytIn, 0, bytIn.Length);

byte[] bytKey = GetLegalKey(Key);

// set the private key
mobjCryptoService.Key = bytKey;
mobjCryptoService.IV = bytKey;

// create a Decryptor from the Provider Service instance
ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();

// create Crypto Stream that transforms a stream using the decryption
CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);

// read out the result from the Crypto Stream
System.IO.StreamReader sr = new System.IO.StreamReader( cs );
return sr.ReadToEnd();
}
}
}