PHP implementation of AES encryption and decryption using openssl_encrypt and openssl_decrypt with initialization vector

php-openssl-crypto-with-iv.php

<?php
    $ENCRYPTION_KEY = "put something secret here";
    $ENCRYPTION_ALGORITHM = 'AES-256-CBC';

    function encrypt($plain_text) {
        global $ENCRYPTION_KEY;
        global $ENCRYPTION_ALGORITHM;
        $EncryptionKey = make_hash($ENCRYPTION_KEY, 32);

        // create random Initialization Vector
        $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length($ENCRYPTION_ALGORITHM));

        $encrypted_text = openssl_encrypt(
            $plain_text,
            $ENCRYPTION_ALGORITHM,
            $EncryptionKey,
            OPENSSL_RAW_DATA,
            $iv 
        );

        # concatenate the IV for decryption
        return  base64_encode($iv . $encrypted_text);
    }

    function decrypt($ciphertext) {
        global $ENCRYPTION_KEY;
        global $ENCRYPTION_ALGORITHM;
        $EncryptionKey = make_hash($ENCRYPTION_KEY, 32);

        $ciphertext = base64_decode($ciphertext);
        // get Initialization Vector part (16 bytes long)
        $iv = substr($ciphertext, 0, 16);
        // rest is actual cipher text
        $ciphertext = substr($ciphertext, 16);

        $decrypted_text = openssl_decrypt(
            $ciphertext,
            $ENCRYPTION_ALGORITHM,
            $EncryptionKey,
            OPENSSL_RAW_DATA,
            $iv
        );

        return $decrypted_text;
    }

    function make_hash($text, $length) {
        $hash_key = hash("sha512", $text, false);
        return substr($hash_key,0,$length);
    }

    // $ct = encrypt("code");
    // $dt = decrypt($ct);
    // echo $ct."\n";
    // echo $dt."\n";
?>