PHP function openssl_encrypt cipher operation failing

Question

I have a PHP script that will encrypt data to store in a database, but when I run the script, the openssl_encrypt returns false with the error: "error:1C800066:Provider routines::cipher operation failed".


    $cipher = str_replace("\n", "", file_get_contents("/key/cipher"));
    $iv_length = openssl_cipher_iv_length($cipher);
    $options = 0;
    $iv = str_replace("\n", "", file_get_contents("/key/iv"));
    $key = str_replace("\n", "", file_get_contents("/key/key"));

    $firstName = openssl_encrypt($data["firstName"], $cipher, $key, $options, $iv);

I have verified that all of these files exist on my pc, as well as $data["firstName"] is actually received.

The data that fails is a first name about 6 characters long, but when I type in an email, which is about 19 characters long, it works perfectly fine.

At least the algorithm ($cipher) is missing, s. MCVE.

Topaco
– Topaco

2024-06-25 14:58:16 +00:00
Commented Jun 25, 2024 at 14:58 — Topaco
– Topaco, Commented Jun 25, 2024 at 14:58

beans-are-gross · Accepted Answer · 2024-06-25 05:47:35Z

0

Even though the cipher I was using aes-256-xts, which is on the list when I call the openssl_get_cipher_methods(); function, I switched to aes-256-ctr and it started working.

answered Jun 25, 2024 at 5:47

beans-are-gross

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2 Comments

Topaco Over a year ago

aes-256-xts refers to AES-256 in XTS mode. XTS is a block cipher mode that does not use padding, but ciphertext stealing, which is why there is a minimum plaintext size of one block (16 bytes). This also explains your issue (encryption of 6 bytes plaintext fails, while 19 bytes plaintext works). Also, the key size is twice as large as usual, e.g. 512 bits for AES-256. XTS is normally used for disk encryption. Instead of an IV, a 128 bit tweak is applied (which is commonly derived from something like the disk sector number).

beans-are-gross Over a year ago

Ok, thank you. I am now realizing I should have included the cipher I was using in the OG question. I also didnt realize what XTS mode was, thank you for the info!

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