MD5和SHA1加密,DES加密和解密，Base64编码解码。

引用命名空间

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

MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();

string md5Str = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(ConvertString)), 4, 8);

return md5Str;

string strpwd1=FormsAuthentication.HashPasswordForStoringInConfigFile("pwd", "SHA1");

string strpwd2=FormsAuthentication.HashPasswordForStoringInConfigFile("pwd", "MD5");

/// <summary>
/// DES加密字符串
/// </summary>
/// <param name="encryptString">待加密的字符串</param>
/// <returns>加密成功返回加密后的字符串，失败返回源串</returns>
public static string DESEncrypt(string encryptString)
{
try
{
byte[] rgbKey = Encoding.UTF8.GetBytes(key.Substring(0, 8));
byte[] rgbIV = rgbKey;
byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
MemoryStream mStream = new MemoryStream();
CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
cStream.Write(inputByteArray, 0, inputByteArray.Length);
cStream.FlushFinalBlock();
cStream.Close();
return Convert.ToBase64String(mStream.ToArray());
}
catch
{
return encryptString;
}
}

/// <summary>
/// DES解密字符串
/// </summary>
/// <param name="decryptString">待解密的字符串</param>
/// <returns>解密成功返回解密后的字符串，失败返源串</returns>
public static string DESDecrypt(string decryptString)
{
try
{
byte[] rgbKey = Encoding.UTF8.GetBytes(key.Substring(0, 8));
byte[] rgbIV = rgbKey;
byte[] inputByteArray = Convert.FromBase64String(decryptString);
DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
MemoryStream mStream = new MemoryStream();
CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
cStream.Write(inputByteArray, 0, inputByteArray.Length);
cStream.FlushFinalBlock();
cStream.Close();
return Encoding.UTF8.GetString(mStream.ToArray());
}
catch
{
return decryptString;
}
}

/// <summary>
/// 将普通字符串编码为BASE64字串
/// </summary>
/// <param name="str">源字符串</param>
/// <returns></returns>
public static string Base64Encode(string str)
{
return Convert.ToBase64String(Encoding.UTF8.GetBytes(str));
}

/// <summary>
/// 解码BASE64字串
/// </summary>
/// <param name="str">Base64字串</param>
/// <returns></returns>
public static string Base64Decode(string base64Str)
{
return Encoding.UTF8.GetString(Convert.FromBase64String(base64Str));
}

UTF-8编码与解码

//对字符串进行UTF-8编码
public static string strUTF(string str)
{
return HttpUtility.UrlEncode(str);
}
//对字符串进行UTF-8解码
public static string strDecode(string str)
{
return HttpUtility.UrlDecode(str);
}

/// <summary>
/// 加密
/// </summary>
/// <param name="str">要加密的</param>
/// <param name="key">钥匙</param>
/// <returns></returns>
public static string Encode(string str, string key)
{
System.Security.Cryptography.DESCryptoServiceProvider provider = new System.Security.Cryptography.DESCryptoServiceProvider();
provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));
provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));
byte[] bytes = Encoding.UTF8.GetBytes(str);
MemoryStream stream = new MemoryStream();
System.Security.Cryptography.CryptoStream stream2 = new System.Security.Cryptography.CryptoStream(stream, provider.CreateEncryptor(), System.Security.Cryptography.CryptoStreamMode.Write);
stream2.Write(bytes, 0, bytes.Length);
stream2.FlushFinalBlock();
StringBuilder builder = new StringBuilder();
foreach (byte num in stream.ToArray())
{
builder.AppendFormat("{0:X2}", num);
}
stream.Close();
return builder.ToString();
}

/// <summary>
/// 解密
/// </summary>
/// <param name="str">要解密的</param>
/// <param name="key">钥匙</param>
/// <returns></returns>
public static string Decode(string str, string key)
{
System.Security.Cryptography.DESCryptoServiceProvider provider = new System.Security.Cryptography.DESCryptoServiceProvider();
provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));
provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));
byte[] buffer = new byte[str.Length / 2];
for (int i = 0; i < (str.Length / 2); i++)
{
int num2 = Convert.ToInt32(str.Substring(i * 2, 2), 0x10);
buffer[i] = (byte)num2;
}
MemoryStream stream = new MemoryStream();
System.Security.Cryptography.CryptoStream stream2 = new System.Security.Cryptography.CryptoStream(stream, provider.CreateDecryptor(), System.Security.Cryptography.CryptoStreamMode.Write);
stream2.Write(buffer, 0, buffer.Length);
stream2.FlushFinalBlock();
stream.Close();
return Encoding.GetEncoding("UTF-8").GetString(stream.ToArray());
}