Today we had the question how to encrypt text in Xojo or PHP and get same results. As both PHP and MBS Plugin can use OpenSSL library to encrypt, we can use the same parameters for both.

In thise case we use AES 256bit with CBC encryption. This requires a key length of 32 bytes exactly, so we use SHA 256 to get from the key a 32 byte key from whatever we have a plain text key. Be aware that different text encoding can produce different keys. So best make sure the key is UTF-8 before hashing. For the initialization vector, we also use a hashed text and pick first 16 bytes. The number of bytes for IV is variable as different encryptions may use different IV lengths.

Here is the example code for Xojo: 

dim keyPlainText as string = "Hello"

dim ivPlainText as string = "test"

dim dataPlaintext as string = "Just a test message. äöü"

dim algorithm as string = "aes-256-cbc"

// init

dim c as CipherMBS = CipherMBS.CipherByName(algorithm)

dim ivLength as integer = c.IVLength

dim keyHash as string = SHA256MBS.Hash(keyPlainText)

dim ivHash as string = SHA256MBS.Hash(ivPlainText)

dim IV as string = leftb(ivHash, ivLength)

// encrypt

call c.EncryptInit keyHash, IV

dim EncryptedData as string = c.ProcessString(dataPlaintext) + c.FinalizeAsString

dim database64 as string = EncodeBase64(EncryptedData, 0)

MsgBox "Key: "+EncodeHex(keyHash)+EndOfLine+_

"IV: "+EncodeHex(IV)+EndOfLine+_

"Data: "+database64

// decrypt

call c.DecryptInit keyHash, IV

dim DecryptedData as string = c.ProcessString(EncryptedData) + c.FinalizeAsString

DecryptedData = DefineEncoding(DecryptedData, encodings.UTF8)

MsgBox DecryptedData 

and the same in PHP: 

<?php

// use of OpenSSL requires PHP 5.3

header('Content-Type: text/plain; charset=UTF-8');

$key = "Hello";

$iv  = "test";

$plaintext = "Just a test message. äöü";

// encrypt with AES 256bit and CBC mode

$algorithm = "aes-256-cbc";

// calculate IV/Key using hash functions

$ivLength = openssl_cipher_iv_length($algorithm);

$keyHash = hash("sha256", $key, true);

$ivHash  = hash("sha256", $iv, true);

$ivHash = substr($ivHash, 0, $ivLength);

// encrypt

$data = openssl_encrypt($plaintext, $algorithm, $keyHash, 0, $ivHash);

echo "Key: " . strToHex($keyHash) . "\n";

echo "IV: " . strToHex($ivHash) . "\n";

echo "Data encrypted: " . $data . "\n";

// decrypt

$data = openssl_decrypt($data, $algorithm, $keyHash, 0, $ivHash);

echo "Data decrypted: " . $data . "\n";

// umlauts show only right if output is read as UTF-8

// helper function to show binary data as hex string

function strToHex($string)

{

    $hex = '';

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

        $hex .= dechex(ord($string[$i]));

    }

    return $hex;

}

?>