对字符串进行SHA1和DES(加密，解密),加密和解密的类

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

namespace StringSecurity
{
/// <summary>
/// 字符串加密解密类。
/// </summary>
public sealed class StringSecurity
{
private StringSecurity() { }

#region SHA1 加密

/// <summary>
/// 使用SHA1加密字符串。
/// </summary>
/// <param name="inputString">输入字符串。</param>
/// <returns>加密后的字符串。（40个字符）</returns>
public static string StringToSHA1Hash(string inputString)
{
SHA1CryptoServiceProvider sha1 = new SHA1CryptoServiceProvider();
byte[] encryptedBytes = sha1.ComputeHash(Encoding.ASCII.GetBytes(inputString));
StringBuilder sb = new StringBuilder();
for (int i = 0; i < encryptedBytes.Length; i++)
{
sb.AppendFormat("{0:x2}", encryptedBytes[i]);
}
return sb.ToString();
}

#endregion

#region DES 加密/解密

private static byte[] key = ASCIIEncoding.ASCII.GetBytes("caikelun");
private static byte[] iv = ASCIIEncoding.ASCII.GetBytes("12345678");

/// <summary>
/// DES加密。
/// </summary>
/// <param name="inputString">输入字符串。</param>
/// <returns>加密后的字符串。</returns>
public static string DESEncrypt(string inputString)
{
MemoryStream ms = null;
CryptoStream cs = null;
StreamWriter sw = null;

DESCryptoServiceProvider des = new DESCryptoServiceProvider();
try
{
ms = new MemoryStream();
cs = new CryptoStream(ms, des.CreateEncryptor(key, iv), CryptoStreamMode.Write);
sw = new StreamWriter(cs);
sw.Write(inputString);
sw.Flush();
cs.FlushFinalBlock();
return Convert.ToBase64String(ms.GetBuffer(), 0, (int)ms.Length);
}
finally
{
if (sw != null) sw.Close();
if (cs != null) cs.Close();
if (ms != null) ms.Close();
}
}

/// <summary>
/// DES解密。
/// </summary>
/// <param name="inputString">输入字符串。</param>
/// <returns>解密后的字符串。</returns>
public static string DESDecrypt(string inputString)
{
MemoryStream ms = null;
CryptoStream cs = null;
StreamReader sr = null;

DESCryptoServiceProvider des = new DESCryptoServiceProvider();
try
{
ms = new MemoryStream(Convert.FromBase64String(inputString));
cs = new CryptoStream(ms, des.CreateDecryptor(key, iv), CryptoStreamMode.Read);
sr = new StreamReader(cs);
return sr.ReadToEnd();
}
finally
{
if (sr != null) sr.Close();
if (cs != null) cs.Close();
if (ms != null) ms.Close();
}
}

#endregion

}
}