Encryption | decryption | algorithm /************************* string Encryption Algorithm ***********************/
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 ();
}
/************************************************** String decryption algorithm **************************************************/
public string decryptstring (String str)
{
if (str. length%4)!=0)
{
throw new ArgumentException ("Not the correct BASE64 encoding, please check.") "," str ");
}
if (! System.Text.RegularExpressions.Regex.IsMatch (str, "^[a-z0-9/+=]*$", System.Text.RegularExpressions.RegexOptions.IgnoreCase))
{
throw new ArgumentException ("contains incorrect BASE64 encoding, please check.") "," 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);
}
Encryption and decryption of files description:
When encrypting a file, it reads the contents of the file into a string variable, encrypts the string, and finally writes the encrypted string to the file. See:
File operation. txt.
