A Solution! AES-128 Encryption between LiveCode and PHP

[keithglong]

Hi All,

Here is an encryption solution for those of you who might need to implement AES-128 encryption between a LiveCode app and a PHP script. I read the following thread (http://forums.livecode.com/viewtopic.ph ... pt#p107448) and found a way to successfully pass an encrypted string from LiveCode to a PHP script for decryption (thanks dcpbarrington!), but I was unable to send encrypted data from a PHP script back to LiveCode for successful decryption. I suspected that the problem had to do with padding, and I was correct. Problem solved! The problem was with the block size and the length of the string to be encrypted.

See the PHP EncryptIt function below. The following code must be included accordingly:

Code: Select all

$blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
 $padding   = $blockSize - (strlen($string) % $blockSize);
 $string   .= str_repeat(chr($padding), $padding);

Please note that your key and iv values must have a length of 16 characters each and must follow certain guidelines. (Please Google Mcrypt and AES 128 encrytion for more details.)

I hope this information helps someone... Here are the sample functions: EncryptIt and DecryptIt for LiveCode, and EncryptIt and DecryptIt for PHP.

Cheers!

- Boo
Gulf Breeze, Florida

LiveCode Code -------------------------------

Code: Select all

function EncryptIt pTokenText
      local tHex, tKeyHex
   
   put "1234567891234567" into tKeyHex
   put "9876543219876543" into tIVHex
   encrypt pTokenText using "aes-128-cbc" with key tKeyHex and IV tIVHex at 128 bit
   put it into tTokenValue
   if the result is Empty then
      return base64Encode( tTokenValue )
   else
      return "Error:" && the result
   end if
   end EncryptIt


function DecryptIt pTokenText
   local tHex, tKeyHex
   
   put base64decode(pTokenText) into pTokenText
   
   put "1234567891234567" into tKeyHex
   put "9876543219876543" into tIVHex
   decrypt pTokenText using "aes-128-cbc" with key tKeyHex and IV tIVHex at 128 bit
   put it into tTokenValue
   if the result is Empty then
      return tTokenValue
   else
      return "Error:" && the result
   end if
   
end DecryptIt

PHP Code -----------------------------

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<?php

$string="LiveCode Rocks!";
$key="1234567891234567";
$iv="9876543219876543";


$encrypted= EncryptIt($string,$key,$iv);

echo $encrypted."<br>";

$decrypted= DecryptIt($encrypted,$key,$iv);

echo $decrypted;


function EncryptIt($string, $key, $iv){

    // This fixes the padding issue so you can decrypt the encrypted string in LiveCode.

    $blockSize = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    $padding   = $blockSize - (strlen($string) % $blockSize);
    $string   .= str_repeat(chr($padding), $padding);

    // Hooray!

    $string = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $string, MCRYPT_MODE_CBC, $iv);

    $string = base64_encode($string);

    return $string;

}

function DecryptIt($string, $key, $iv){

    $string = base64_decode($string);

    $string = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $string, MCRYPT_MODE_CBC, $iv);

return $string;

}

?>

[sphere]

Thanks very much!
Maybe this comes in handy in future projects.

Cheers!

Sphere