Simple 2-way encryption

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July 19th, 2002, 11:44 PM

MercuryBoard

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Simple 2-way encryption

I'm looking for a 2-way algorithm that can convert a string into an alphanumeric string that doesn't resemble the original. Can this be done?

(This is for a PHP script)

Basically what I want to do is take a few pieces of information such as the below, related to an error message, and put them together so it can be transmitted easily through a URL. It would be an added bonus to keep this data fairly secure.

Quote:

4.2.1
3.23.49
Apache
The database could not connect.

July 20th, 2002, 03:47 AM

Scorpions4ever

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Maybe you can use some prewritten modules for PHP, such as the Mcrypt module. http://www.onlamp.com/pub/a/php/200...ypt.html?page=3

If you want the algorithm descriptions for the sake of learning, I'd recommend buying a copy of Bruce Schneier's "Applied Cryptography" where he discusses the relative strengths and weaknesses of many cryptographic algorithms.

Hope this helps.

July 26th, 2002, 11:35 AM

mrTed

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Hi,

I did an 2 way encryption algorith class for php and a vbscript sub a while back. If it is of use to you let me know and I will dig it out?

Regards, Ed.

__________________
/* measure twice, cut once */

July 26th, 2002, 02:23 PM

MercuryBoard

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Basically I need something to obscure data and make it transmittable by URL, where it can then be unobscured. Encryption would be a plus but basically I need something simpler.

July 30th, 2002, 11:13 AM

mrTed

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Hi MercuryBoard,

No problem. If you don't get sorted and need the code let me know.

Regards, Ed.

July 30th, 2002, 11:27 AM

MercuryBoard

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I'm interested... Send me the code

August 2nd, 2002, 11:40 AM

mrTed

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Hi,

Sorry for the delay, I couldn't remember where I had put it?
I think it will be secure enough if the data is not too critical

The Class...

PHP Code:


		
			
<?

//Encryption class

Class cls_encrypt{



var $s_array = array();

var $K_array = array();

var $return_val;

var $num_count;

var $alp_count;

var $lwr_count;



    //Function to return the decimal value of an ascii character...

    function get_ascii_val($passed_val){

        //This assigns all the ascii vals to the $asc_chars() array...

        for($x_val = 0; $x_val <= 255; $x_val = $x_val + 1){

            $asc_chars[chr($x_val)] = $x_val; 

        }

        return $asc_chars[$passed_val];

    } 



    //Basic function to encrypt/decrypt. Input_val gets crypted/decrypted using key_val... 

    Function encrypt_value($input_val, $key_val){

        //Create an array of 0 - 255 and initialise 

        for ($i = 0; $i <= 255; $i = $i + 1){

            $s_array[$i] = $i;

        }  



        //

        $j = 1;

        //Create an array of 0 - 255 and initialise with a calculated chr value...

        for ($i = 0; $i <= 255; $i = $i + 1){

            if ($j > strlen($key_val)){

                $j = 1;

            }

            $K_array[$i] = $this -> get_ascii_val(substr($key_val, $j, 1));

            $j = $j + 1;

        }

        

        //Shuffle the array values around to give a 'random' value...

        $j = 0;

        for ($i = 0; $i <= 255; $i = $i + 1){

            $j = ($j + $s_array[$i] + $K_array[$i]) % 256;

            $temp_var = $s_array[$i];

            $s_array[$i] = $s_array[$j];

            $s_array[$j] = $temp_var;

        }

        

        //Create the 'encrypted' string from the 2 initialised arrays...

        $i = 0;

        $j = 0;

        for ($x = 0; $x < strlen($input_val); $x++){

            $i = ($i + 1) % 256;

            $j = ($j + $s_array[$i]) % 256;

            $temp_var = $s_array[$i];

            $s_array[$i] = $s_array[$j];

            $s_array[$j] = $temp_var;

            $t = ($s_array[$i] + ($s_array[$j] % 256)) % 256;

            $y = $s_array[$t];

            $comp_val = $this -> get_ascii_val(substr($input_val, $x, 1)) ^ $y;

            $calc_val = Chr($this -> get_ascii_val(substr($input_val, $x, 1)) ^ $y);

            $return_val = $return_val.$calc_val;

        }

        return $return_val;

    }

}

?>

... And something to test it with (gives an idea of what it does...

PHP Code:


		
			
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<html>

<head>

    <title>Encrypt...</title>

</head>



<body>

<? 

if (isset($_POST[submit])){

    include("addEncryptClasses.inc.php");

    $my_obj = new cls_encrypt();

    $obscure_text = $my_obj -> encrypt_value($_POST[enctext], $_POST[enckey]);

    echo "Text is : ".$_POST[enctext]."<br>";

    echo "Key is : ".$_POST[enckey]."<br>";

    echo "Obscured Text is : ".$obscure_text."<br><br>";

    echo "Re-enter the key to un-obscure the text!<br><br>";

}

?>



<table cellspacing="2" cellpadding="2" border="0">

<form action="" method="post">

<tr>

    <td>

        Enter the text to be obscured or unobscured 

    </td>

</tr>

<tr>

    <td><input type="text" name="enctext" value="<? echo $secure_text; ?>" size="100"></td>

</tr>

<tr>

    <td>Enter the key</td>

</tr>

<tr>

    <td><input type="text" name="enckey"></td>

</tr>

<tr>

    <td><input type="submit" name="submit"></td>

</tr>

</form>

</table>



</body>

</html>

I used it originally for storing values in a db as encrypted strings, then used it to store stuff in sessions etc.

It is probably a little hungry for day to day use if there is a lot of data but I think you could easily reduce the number of chars in the encryption routine from 256 to say 40 or 50. If I get a bit of time this week I will sort it out and let you know.

The other reason to reduce the amount of chars used it that this currently uses *ALL* the ascii char set, as opposed to just alphanumeric chars which would be a load better for passing in the URL.

Hope it helps you out anyway.

Regards, Ed.

August 2nd, 2002, 12:06 PM

Dingle

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heres one that ive used before, i'm not sure where i got it but it seems to work pretty well

PHP Code:


		
			
class rc4crypt {

    function endecrypt ($pwd, $data, $case='') {

        if ($case == 'de') {

            $data = urldecode($data);

        }



        $key[] = "";

        $box[] = "";

        $temp_swap = "";

        $pwd_length = 0;



        $pwd_length = strlen($pwd);



        for ($i = 0; $i <= 255; $i++) {

            $key[$i] = ord(substr($pwd, ($i % $pwd_length), 1));

            $box[$i] = $i;

        }



        $x = 0;



        for ($i = 0; $i <= 255; $i++) {

            $x = ($x + $box[$i] + $key[$i]) % 256;

            $temp_swap = $box[$i];



            $box[$i] = $box[$x];

            $box[$x] = $temp_swap;

        }



        $temp = "";

        $k = "";



        $cipherby = "";

        $cipher = "";



        $a = 0;

        $j = 0;



        for ($i = 0; $i < strlen($data); $i++) {

            $a = ($a + 1) % 256;

            $j = ($j + $box[$a]) % 256;



            $temp = $box[$a];

            $box[$a] = $box[$j];



            $box[$j] = $temp;



            $k = $box[(($box[$a] + $box[$j]) % 256)];

            $cipherby = ord(substr($data, $i, 1)) ^ $k;



            $cipher .= chr($cipherby);

        }



        if ($case == 'de') {

            $cipher = urldecode(urlencode($cipher));



        } else {

            $cipher = urlencode($cipher);

        }



        return $cipher;

    }

}



####### USAGE ###########



$thestring = "the quick brown fox";

$thepasswd = "mypassword";



$rc4 = new rc4crypt;



$thestring = $rc4->endecrypt($thepasswd,$thestring);

## $thestring is now encrypted



$thestring = $rc4->endecrypt($thepasswd,$thestring,'de');

## $thestring is now decrypted

August 31st, 2011, 03:28 PM

nilesh4life

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Thank You

Dingle,

I registered on forum JUST to say to Thank you! The code is pretty old and working pretty good.

Simple 2-way encryption

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