ISO9797 MAC algorithm 3

ISO9797Algorithm3.php

<?php
class ISO9797Algorithm3 {

    const BLOCK_SIZE = 8;
    const KEY_SIZE = 8;

    public static function generate($input, $key) {
        $inputChunked = str_split($input, self::BLOCK_SIZE);
        $desKeys = self::splitKey($key);
        $output = str_pad("", self::BLOCK_SIZE, "\0");
        foreach ($inputChunked as $chunk) {
            if (strlen($chunk) !== self::BLOCK_SIZE) {
                $chunk = str_pad($chunk, self::BLOCK_SIZE, "\0");
            }
            $output = openssl_encrypt($chunk, "DES-CBC", $desKeys[0], OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING, $output);
        }
        $output = openssl_decrypt($output, "DES-ECB", $desKeys[1], OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING);
        return openssl_encrypt($output, "DES-ECB", $desKeys[2], OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING);
    }

    public static function generateKey() {
        return self::key(self::KEY_SIZE * 2);
    }

    public static function generate3DesKey() {
        return self::key(self::KEY_SIZE * 3);
    }

    private static function key($size) {
        $key = str_pad("", $size, "\0");
        for ($i = 0; $i < $size; $i++) {
            $key[$i] = mt_rand() % 255;
        }
        return $key;
    }

    private static function splitKey($key) {
        $keySize = strlen($key);
        if (!in_array($keySize, [24, 16])) {
            throw new InvalidArgumentException("Key must be size of 24 or 16 bytes");
        }

        $keys = str_split($key, self::BLOCK_SIZE);
        if($keySize === 16){
            $keys[] = $keys[0];
        }
        return $keys;
    }

}