Please help a PHP newbie :.

max_demon · 25-02-2009, 11:14 PM

Hello dear friends ,

I need help creating a php script which does the following

has a input box to enter encrypted data
submit button
then i have a decrypt.php file which should be used as decryption criteria for encrypted data
after that the result should be visible in the screen

please guys this is very important i have to decrypt a message

; the decryption file i got from a hacker like person . and i have been challanged to decrypt .

if anyone can help u can come to my yahoo messenger ID at max_demon123 i will give u decrypt.php .

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victor_rambo · 26-02-2009, 12:10 AM

Well, I could help if I know how the data has been encoded.

Frankly, I think you must give up the challenge because

max_demon · 26-02-2009, 09:49 AM

split 8 bit to 4 bit

multiply by 4 plus m where m=0,1,2, or 3

convert to base64 value

convert decimal value into base64 value

>>THese are the steps i think most probebly

This is encryption process

Code:

   
   $key_length=0;
   $all_bin_chars="";
   $cipher_data="";
    
   for($i=0;$i<strlen($plain_data);$i++){
    $p=substr($plain_data,$i,1);
    $k=substr($key,$key_length,1);
    $key_length++;
    
    if($key_length>=strlen($key)){
        $key_length=0;
    }
    
    $dec_chars=ord($p)^ord($k);
    $dec_chars=$dec_chars + strlen($key);
    $bin_chars=decbin($dec_chars);
    
    while(strlen($bin_chars)<8){
        $bin_chars="0".$bin_chars;
    }
        
    $all_bin_chars=$all_bin_chars.$bin_chars;
    
   }
    
   $m=0;

   for($j=0;$j<strlen($all_bin_chars);$j=$j+4){
    $four_bit=substr($all_bin_chars,$j,4);     
    $four_bit_dec=bindec($four_bit);

    $decimal_value=$four_bit_dec * 4 + $m;

    $base64_value=dectobase64($decimal_value);
    $cipher_data=$cipher_data.$base64_value;
    $m++;
    
    if($m>3){
        $m=0;
    }
   }
   
   return $cipher_data;
}        

function dectobase64($decimal_value){

   switch($decimal_value){
    case 0: $base64_value="A";break;
    case 1: $base64_value="B";break;
    case 2: $base64_value="C";break;
    case 3: $base64_value="D";break;
    case 4: $base64_value="E";break;
    case 5: $base64_value="F";break;
    case 6: $base64_value="G";break;
    case 7: $base64_value="H";break;
    case 8: $base64_value="I";break;
    case 9: $base64_value="J";break;
    case 10: $base64_value="K";break;
    case 11: $base64_value="L";break;
    case 12: $base64_value="M";break;
    case 13: $base64_value="N";break;
    case 14: $base64_value="O";break;
    case 15: $base64_value="P";break;
    case 16: $base64_value="Q";break;
    case 17: $base64_value="R";break;
    case 18: $base64_value="S";break;
    case 19: $base64_value="T";break;
    case 20: $base64_value="U";break;
    case 21: $base64_value="V";break;
    case 22: $base64_value="W";break;
    case 23: $base64_value="X";break;
    case 24: $base64_value="Y";break;
    case 25: $base64_value="Z";break;
    case 26: $base64_value="a";break;
    case 27: $base64_value="b";break;
    case 28: $base64_value="c";break;
    case 29: $base64_value="d";break;
    case 30: $base64_value="e";break;
    case 31: $base64_value="f";break;
    case 32: $base64_value="g";break;
    case 33: $base64_value="h";break;
    case 34: $base64_value="i";break;
    case 35: $base64_value="j";break;
    case 36: $base64_value="k";break;
    case 37: $base64_value="l";break;
    case 38: $base64_value="m";break;
    case 39: $base64_value="n";break;
    case 40: $base64_value="o";break;
    case 41: $base64_value="p";break;
    case 42: $base64_value="q";break;
    case 43: $base64_value="r";break;
    case 44: $base64_value="s";break;
    case 45: $base64_value="t";break;
    case 46: $base64_value="u";break;
    case 47: $base64_value="v";break;
    case 48: $base64_value="w";break;
    case 49: $base64_value="x";break;
    case 50: $base64_value="y";break;
    case 51: $base64_value="z";break;
    case 52: $base64_value="0";break;
    case 53: $base64_value="1";break;
    case 54: $base64_value="2";break;
    case 55: $base64_value="3";break;
    case 56: $base64_value="4";break;
    case 57: $base64_value="5";break;
    case 58: $base64_value="6";break;
    case 59: $base64_value="7";break;
    case 60: $base64_value="8";break;
    case 61: $base64_value="9";break;
    case 62: $base64_value="+";break;
    case 63: $base64_value="/";break;
    case 64: $base64_value="=";break;
    default: $base64_value="a";break;
   }
   
   return $base64_value;
}

This is decryption process

Code:

<?php


function changedataout($cipher_data,$key){


   $m=0;
   $all_bin_chars="";
    
   for($i=0;$i<strlen($cipher_data);$i++){
    $c=substr($cipher_data,$i,1);             // c = ciphertext
    $decimal_value=base64todec($c);           //convert to decimal value
    
    $decimal_value=($decimal_value - $m) / 4; //substract by m where m=0,1,2,or 3 then divide by 4
    
    $four_bit=decbin($decimal_value);
    
    while(strlen($four_bit)<4){
        $four_bit="0".$four_bit;
    }
    
    $all_bin_chars=$all_bin_chars.$four_bit;
    $m++;
    
    if($m>3){
        $m=0;
    }
   }
    
   $key_length=0;
   $plain_data="";
    
   for($j=0;$j<strlen($all_bin_chars);$j=$j+8){
    $c=substr($all_bin_chars,$j,8);
    $k=substr($key,$key_length,1);
    
    $dec_chars=bindec($c);
    $dec_chars=$dec_chars - strlen($key);
    $c=chr($dec_chars);
    $key_length++;
    
    if($key_length>=strlen($key)){
        $key_length=0;
    }
    
    $dec_chars=ord($c)^ord($k);
    $p=chr($dec_chars);
    $plain_data=$plain_data.$p;
   }
   
   return $plain_data;
}

function base64todec($base64_value){

   // convert base64 value into decimal value

   switch($base64_value){
    case "A":$decimal_value=0;break;
    case "B":$decimal_value=1;break;
    case "C":$decimal_value=2;break;
    case "D":$decimal_value=3;break;
    case "E":$decimal_value=4;break;
    case "F":$decimal_value=5;break;
    case "G":$decimal_value=6;break;
    case "H":$decimal_value=7;break;
    case "I":$decimal_value=8;break;
    case "J":$decimal_value=9;break;
    case "K":$decimal_value=10;break;
    case "L":$decimal_value=11;break;
    case "M":$decimal_value=12;break;
    case "N":$decimal_value=13;break;
    case "O":$decimal_value=14;break;
    case "P":$decimal_value=15;break;
    case "Q":$decimal_value=16;break;
    case "R":$decimal_value=17;break;
    case "S":$decimal_value=18;break;
    case "T":$decimal_value=19;break;
    case "U":$decimal_value=20;break;
    case "V":$decimal_value=21;break;
    case "W":$decimal_value=22;break;
    case "X":$decimal_value=23;break;
    case "Y":$decimal_value=24;break;
    case "Z":$decimal_value=25;break;
    case "a":$decimal_value=26;break;
    case "b":$decimal_value=27;break;
    case "c":$decimal_value=28;break;
    case "d":$decimal_value=29;break;
    case "e":$decimal_value=30;break;
    case "f":$decimal_value=31;break;
    case "g":$decimal_value=32;break;
    case "h":$decimal_value=33;break;
    case "i":$decimal_value=34;break;
    case "j":$decimal_value=35;break;
    case "k":$decimal_value=36;break;
    case "l":$decimal_value=37;break;
    case "m":$decimal_value=38;break;
    case "n":$decimal_value=39;break;
    case "o":$decimal_value=40;break;
    case "p":$decimal_value=41;break;
    case "q":$decimal_value=42;break;
    case "r":$decimal_value=43;break;
    case "s":$decimal_value=44;break;
    case "t":$decimal_value=45;break;
    case "u":$decimal_value=46;break;
    case "v":$decimal_value=47;break;
    case "w":$decimal_value=48;break;
    case "x":$decimal_value=49;break;
    case "y":$decimal_value=50;break;
    case "z":$decimal_value=51;break;
    case "0":$decimal_value=52;break;
    case "1":$decimal_value=53;break;
    case "2":$decimal_value=54;break;
    case "3":$decimal_value=55;break;
    case "4":$decimal_value=56;break;
    case "5":$decimal_value=57;break;
    case "6":$decimal_value=58;break;
    case "7":$decimal_value=59;break;
    case "8":$decimal_value=60;break;
    case "9":$decimal_value=61;break;
    case "+":$decimal_value=62;break;
    case "/":$decimal_value=63;break;
    case "=":$decimal_value=64;break;
    default: $decimal_value=0;break;
   }
   
   return $decimal_value;
}
?>

THis is decrypt.php , any help . ? please guys i am stuck how to put input and what is variable

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