C#字符和文件加密类

字符和文件加密类，128位加密

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

namespace MySecurity 
{ 
public class MySecurity 
{ 
public MySecurity() 
{ 
// 
// TODO: 在此处添加构造函数逻辑 
// 
} 
private string key="1234567890"; //默认密钥 

private byte[] sKey; 
private byte[] sIV; 

/// <summary> 
/// 加密字符串 
/// </summary> 
/// <param name="inputStr">输入字符串</param> 
/// <param name="keyStr">密码，可以为“”</param> 
/// <returns>输出加密后字符串</returns> 

static public string SEncryptString(string inputStr,string keyStr) 
{ 
MySecurity ws=new MySecurity(); 
return ws.EncryptString(inputStr,keyStr); 
} 

/// <summary> 
/// 加密字符串 
/// </summary> 
/// <param name="inputStr">输入字符串</param> 
/// <param name="keyStr">密码，可以为“”</param> 
/// <returns>输出加密后字符串</returns> 
public string EncryptString(string inputStr,string keyStr) 
{ 
DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 
if(keyStr=="") 
keyStr=key; 
byte[] inputByteArray = Encoding.Default.GetBytes(inputStr); 
byte[] keyByteArray=Encoding.Default.GetBytes(keyStr); 
SHA1 ha=new SHA1Managed(); 
byte[] hb=ha.ComputeHash(keyByteArray); 
sKey=new byte[8]; 
sIV=new byte[8]; 
for(int i=0;i<8;i++) 
sKey[i]=hb[i]; 
for(int i=8;i<16;i++) 
sIV[i-8]=hb[i]; 
des.Key=sKey; 
des.IV=sIV; 
MemoryStream ms = new MemoryStream();