openssl_decrypt always returns false

Question

I tried to migrate my encryption from mcrypt to openssl but the decryption keeps failing. The code Below shows my encryption function. I placed the var_dump in the encryption function to verify decryption with identical variables works, which it does not.

I tried the following changes to the code, none worked:

base64_decode($encrypted)
just out of curiosity base64_encode($encrypted)
all these variants with options set to:0(default value),OPENSSL_RAW_DATA,OPENSSL_ZERO_PADDING

function encryptString($data){  
    $key = "1A534";

    do{
        $iv = random_bytes(100);
    }while(strpos($iv,"|Z|")!==false);

    $encrypted = openssl_encrypt($data,"aes-256-gcm",$key,false,$iv);   
    var_dump(openssl_decrypt($encrypted,"aes-256-gcm",$key,OPENSSL_RAW_DATA,$iv));
    $output = $iv . "|Z|" . $encrypted;
    $output = base64_encode($output);   
    return $output;
}

PHP Version is 7.0.5-1+deb.sury.org~trusty+1

OpenSSL Version is OpenSSL 1.0.2g 1 Mar 2016

Why keeps openssl_decrypt returning false? I successfully encrypted with the same variables just the line above.

I think this won't work until PHP 7.1, because there is a bug with the authentication tag. — Artjom B.
– Artjom B., Commented Mar 31, 2016 at 20:29
I'm using 7.1 in this scenario but still getting a false returned in all scenarios. — Dockstar
– Dockstar, Commented Oct 18, 2017 at 15:15

Spomky-Labs · Accepted Answer · 2018-09-12 06:05:05Z

1

It will not work for PHP < 7.1 as AEAD is not supported.

You can use the library I created (PHP 5.4+ and 7.0+).

Depending on your environment, it will test and use the following methods:

OpenSSL on PHP 7.1,
libCrypto extension,
A pure PHP implementation.

Note that the pure PHP method is very slow compared to the other methods.

edited Sep 12, 2018 at 6:05

answered Jan 1, 2017 at 15:40

Spomky-Labs

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