Convert Java AES encryption to PHP

Question

I have a requirement to use AES encryption with specific parameters but the only example provided is in Java. I need to move everything to PHP and I'm not sure how to do it exactly.

In Java the encryption class takes the iv/salt parameters as an array of bytes directly. Something in the likes of:

byte[] iv = {(byte) 0xCB, (byte) 0x35, (byte) 0xF3, (byte) 0x52, (byte) 0x1A, (byte) 0xF7, (byte) 0x38, (byte) 0x0B, (byte) 0x75, (byte) 0x03, (byte) 0x8E, (byte) 0xE0, (byte) 0xEF, (byte) 0x39, (byte) 0x98, (byte) 0xC7};
AlgorithmParameterSpec params = new IvParameterSpec(iv);

but PHP expects a string for input, so I tried to do something like:

private $salt = ['a7', '70', '1f', 'f6', '5e', 'd3', '29', '8f'];
private $iv = ['cb', '35', 'f1', '52', '1b', 'f7', '33', '0b', '75', '03', '8e', 'e0', 'cf', '39', '98', 'c7'];
 public function __construct()
{
 $iv = implode(array_map("hex2bin", $this->iv));
 $this->iv = $iv;
 $salt = implode(array_map("hex2bin", $this->salt));
 $this->salt = $salt;
}
public function encrypt($unencryptedString)
{
 $key = hash_pbkdf2('sha1', $this->passPhrase, $this->salt, $this->iterationCount, $this->keyLen, true);
 var_dump($key);
 $hash = openssl_encrypt($unencryptedString, 'AES-128-CBC', $key, OPENSSL_RAW_DATA, $this->iv);
 $encoded = base64_encode($hash);
 return $encoded;
}

I imagine I'm not using the iv/salt parameters the same way its used on Java, thats why it doesn't produce the same thing. Suggestions?

Answer 1

Basics (You did good!)

You should always Use a standard library for PHP encryption.

I know we shouldn't be making recommendations but encryption is in my opinion somewhat of an exception and you should utilise tried and tested libraries.

Use either the openssl extensions or libsodium

Answers on using both are linked here.

How to encrypt plaintext with AES-256 CBC in PHP using openssl()?

How to encrypt / decrypt AES with Libsodium-PHP

Problems?

In terms of your implemtation I think the $iv and $key aren't well formed inputs for hex2bin()

$iv = ['0xA7', '0x71', '0x1F', '0xF5', '0x5D', '0xD2', '0x28', '0x8F'];
array_map("hex2bin", $iv);
// outputs Warning: hex2bin(): Input string must be hexadecimal string

• Pedro: Hi Luke, thanks for the feedback. I'm using openssl extension already, just not sure how to feed the parameters correctly... These examples use random keys as example.
• Pedro: thanks for the update, its a good starting point. I updated the iv/salt values to have everything in lowercase.
• Pedro: I can find the matches for hex values in here: numbermonk.com/hexadecimal/203/en but PHP keeps showing the same error, any idea?
• Luke: the 0xA7 i believe should just be 00A7 - I think the 0x notation is to let humans know the encoding is hex

Answer 2

Following @Luke's suggestion:

Removing 0x and using lower case in all iv/salt values seems to do it.

private $salt = ['a7', '71', '1f', 'f5', '5d', 'd2', '28', '8f'];