后面的乱码是随机生成的字符，加这些字符的含义，是为了使以扩展名为搜索条件的软件失效。
可以用随机生成数制作随机数字，Random.Next()方法。
例如：
<img src="../../xx.jpg?<% =Random.Next(100000-999999) %> >
可以用随机生成数制作随机数字，Random.Next()方法。
例如：
<img src="../../xx.jpg?<% =Random.Next(100000-999999) %> >
using System;
using System.Security.Cryptography;
using System.IO;
using System.Text;namespace FangHome_Crypto
{
/// <summary>
/// SymmCrypto is a wrapper of System.Security.Cryptography.SymmetricAlgorithm classes
/// and simplifies the interface. It supports customized SymmetricAlgorithm as well.
/// </summary>
public class SymmCrypto
{
/// <res>
/// Supported .Net intrinsic SymmetricAlgorithm classes.
/// </res>
public enum SymmProvEnum : int
{
DES, RC2, Rijndael
} private SymmetricAlgorithm mobjCryptoService; /// <res>
/// Constructor for using an intrinsic .Net SymmetricAlgorithm class.
/// </res>
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;
}
} /// <res>
/// Constructor for using a customized SymmetricAlgorithm class.
/// </res>
public SymmCrypto(SymmetricAlgorithm ServiceProvider)
{
mobjCryptoService = ServiceProvider;
} /// <res>
/// 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.
/// </res>
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();
}
}
}