.net如何加密與解密的算法

MD5對字符串的加密

System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(temp_str, "MD5");

若想加密後能解密，可採用Des方法，例子如下：
#region Des加密/解密算法.
/// <summary>
/// 加密字符串
/// </summary>
/// <param name="pToEncrypt">待加密字符串</param>
/// <returns></returns>
public string Encrypt(string pToEncrypt)
{
byte[] desKey = new byte[]{0x16, 0x09, 0x14, 0x15, 0x07, 0x01, 0x05, 0x08};
byte[] desIV = new byte[]{0x16, 0x09, 0x14, 0x15, 0x07, 0x01, 0x05, 0x08};
DESCryptoServiceProvider des = new DESCryptoServiceProvider();
try
{
//把字符串放到byte數組中.
//原來使用的UTF8編碼，我改成Unicode編碼了，不行.
byte[] inputByteArray = Encoding.Default.GetBytes(pToEncrypt);
//byte[] inputByteArray=Encoding.Unicode.GetBytes(pToEncrypt);
//建立加密對象的密鑰和偏移量.
//原文使用ASCIIEncoding.ASCII方法的GetBytes方法.
//使得輸入密碼必須輸入英文文本.
des.Key = desKey; // ASCIIEncoding.ASCII.GetBytes(sKey);
des.IV = desIV; //ASCIIEncoding.ASCII.GetBytes(sKey);
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(),CryptoStreamMode.Write);
//Write the byte array into the crypto stream.
//(It will end up in the memory stream)
cs.Write(inputByteArray, 0, inputByteArray.Length);
cs.FlushFinalBlock();
//Get the data back from the memory stream, and into a string.
StringBuilder ret = new StringBuilder();
foreach(byte b in ms.ToArray())
{
//Format as hex.
ret.AppendFormat("{0:X2}", b);
}
ret.ToString();
return ret.ToString();
}
catch
{
return pToEncrypt;
}
finally
{
des = null;
}
}
/// <summary>
/// 解密字符串
/// </summary>
/// <param name="pToDecrypt">待解密字符串</param>
/// <returns></returns>
public string Decrypt(string pToDecrypt)
{
byte[] desKey = new byte[]{0x16, 0x09, 0x14, 0x15, 0x07, 0x01, 0x05, 0x08};
byte[] desIV = new byte[]{0x16, 0x09, 0x14, 0x15, 0x07, 0x01, 0x05, 0x08};

DESCryptoServiceProvider des = new DESCryptoServiceProvider();
try
{
//Put the input string into the byte array.
byte[] inputByteArray = new byte[pToDecrypt.Length / 2];
for(int x = 0; x < pToDecrypt.Length / 2; x++)
{
int i = (Convert.ToInt32(pToDecrypt.Substring(x * 2, 2), 16));
inputByteArray[x] = (byte)i;
}
//建立加密對象的密鑰和偏移量，此值重要，不能修改.
des.Key = desKey; //ASCIIEncoding.ASCII.GetBytes(sKey);
des.IV = desIV; //ASCIIEncoding.ASCII.GetBytes(sKey);
MemoryStream ms = new MemoryStream();
CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(),CryptoStreamMode.Write);
//Flush the data through the crypto stream into the memory stream.
cs.Write(inputByteArray, 0, inputByteArray.Length);
cs.FlushFinalBlock();
//Get the decrypted data back from the memory stream.
//建立StringBuild對象，CreateDecrypt使用的是流對象，必須把解密後的文本變成流對象.
StringBuilder ret = new StringBuilder();
return System.Text.Encoding.Default.GetString(ms.ToArray());
}
catch
{
return pToDecrypt;
}
finally
{
des = null;
}
}
#endregion

 

http://hi.baidu.com/jonesvale/blog/item/ec586d589ddf8f222934f00a.html