[VB6/VBA] Simple AES 256-bit password protected encryption

[wqweto]

Here is the equivalent php implementation with compatible arguments for the pbkdf2 key derivation

<?php
const CIPHER = "AES-256-CTR";
const KEYLEN = 32;
const IVLEN = 16;
const KDF_SALTLEN = 8;
const KDF_ITER = 10000;
const KDF_HASH = "SHA512";
const OPENSSL_MAGIC = "Salted__";
const OPENSSL_MAGICLEN = 8;

function AesEncryptString($text, $password)
{
    $salt = openssl_random_pseudo_bytes(KDF_SALTLEN);
    $derived = openssl_pbkdf2($password, $salt, KEYLEN + IVLEN, KDF_ITER, KDF_HASH);
    $encr = openssl_encrypt($text, CIPHER, substr($derived, 0, KEYLEN), OPENSSL_RAW_DATA, substr($derived, KEYLEN, IVLEN));
    return base64_encode(OPENSSL_MAGIC . $salt . $encr);
}

function AesDecryptString($encr, $password)
{
    $encr = base64_decode($encr);
    $salt = "";
    if (substr($encr, 0, OPENSSL_MAGICLEN) == OPENSSL_MAGIC) {
        $salt = substr($encr, OPENSSL_MAGICLEN, KDF_SALTLEN);
        $encr = substr($encr, OPENSSL_MAGICLEN + KDF_SALTLEN);
    }
    $derived = openssl_pbkdf2($password, $salt, KEYLEN + IVLEN, KDF_ITER, KDF_HASH);
    return openssl_decrypt($encr, CIPHER, substr($derived, 0, KEYLEN), OPENSSL_RAW_DATA, substr($derived, KEYLEN, IVLEN));
}

$encr = AesEncryptString("this is a PHP test това е проба", "password123");
echo $encr . "\n";
echo AesDecryptString($encr, "password123") . "\n";
?>

cheers,
</wqw>