/*************************字符串加密算法***********************/
public string EncryptString(string str)
{
char[] Base64Code=new char[]{'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','0','1','2','3','4','5','6','7','8','9','+','/','='};
byte empty=(byte)0;
System.Collections.ArrayList byteMessage=new System.Collections.ArrayList(System.Text.Encoding.Default.GetBytes(str));
System.Text.StringBuilder outmessage;
int messageLen=byteMessage.Count;
int page=messageLen/3;
int use=0;
if((use=messageLen%3)>0)
{
for(int i=0;i<3-use;i++)
byteMessage.Add(empty);
page++;
}
outmessage=new System.Text.StringBuilder(page*4);
for(int i=0;i<page;i++)
{
byte[] instr = new byte[3];
instr[0]=(byte)byteMessage[i*3];
instr[1]=(byte)byteMessage[i*3+1];
instr[2]=(byte)byteMessage[i*3+2];
int[] outstr=new int[4];
outstr[0]=instr[0]>>2;
outstr[1]=((instr[0]&0x03)<<4)^(instr[1]>>4);
if(!instr[1].Equals(empty))
outstr[2]=((instr[1]&0x0f)<<2)^(instr[2]>>6);
else
outstr[2]=64;
if(!instr[2].Equals(empty))
outstr[3]=(instr[2]&0x3f);
else
outstr[3]=64;
outmessage.Append(Base64Code[outstr[0]]);
outmessage.Append(Base64Code[outstr[1]]);
outmessage.Append(Base64Code[outstr[2]]);
outmessage.Append(Base64Code[outstr[3]]);
}
return outmessage.ToString();
}
/**************************************************字符串解密算法**************************************************/
public string DecryptString(string str)
{
if((str.Length%4)!=0)
{
throw new ArgumentException("不是正确的BASE64编码，请检查。","str");
}
if(!System.Text.RegularExpressions.Regex.IsMatch(str,"^[A-Z0-9/+=]*$",System.Text.RegularExpressions.RegexOptions.IgnoreCase))
{
throw new ArgumentException("包含不正确的BASE64编码，请检查。","str");
}
string Base64Code="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+/=";
int page=str.Length/4;
System.Collections.ArrayList outMessage=new System.Collections.ArrayList(page*3);
char[] message=str.ToCharArray();
for(int i=0;i<page;i++)
{
byte[] instr=new byte[4];
instr[0]=(byte)Base64Code.IndexOf(message[i*4]);
instr[1]=(byte)Base64Code.IndexOf(message[i*4+1]);
instr[2]=(byte)Base64Code.IndexOf(message[i*4+2]);
instr[3]=(byte)Base64Code.IndexOf(message[i*4+3]);
byte[] outstr=new byte[3];
outstr[0]=(byte)((instr[0]<<2)^((instr[1]&0x30)>>4));
if(instr[2]!=64)
{
outstr[1]=(byte)((instr[1]<<4)^((instr[2]&0x3c)>>2));
}
else
{
outstr[2]=0;
}
if(instr[3]!=64)
{
outstr[2]=(byte)((instr[2]<<6)^instr[3]);
}
else
{
outstr[2]=0;
}
outMessage.Add(outstr[0]);
if(outstr[1]!=0)
outMessage.Add(outstr[1]);
if(outstr[2]!=0)
outMessage.Add(outstr[2]);
}
byte[] outbyte=(byte[])outMessage.ToArray(Type.GetType("System.Byte"));
return System.Text.Encoding.Default.GetString(outbyte);
}
文件的加密解密说明：
在对文件进行加密解密时，先将文件的内容读取到一个字符串变量中，然后对字符串加密，最后再把加密后的字符串写入到文件中。详见:
文件操作.txt。
