Laravel - How to Encrypt and Decrypt Large Files in Chunks?

I was initially encrypting files directly without using chunks and started encountering an error when trying to encrypt large files:

Allowed memory size of 134217728 bytes exhausted

After some research, I found out I was making a big mistake by trying to encrypt directly by doing something like:

Storage::put($filePath, $encrypted->encrypt(file_get_contents($file)));

This is a bad idea because it will load the entire file into memory, as well as the encrypted version. For small files, this works fine but not for large files because it will exceed PHP memory_limit.

To address this, I decided to implement encryption and decryption in chunks. I want to use the Encrypter class provided by Laravel but I am running into some issues. This is what I tried:

Note: The following routes are for testing purposes.

Encryption

use Illuminate\Encryption\Encrypter;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Config;
use Illuminate\Support\Facades\Route;
use Illuminate\Support\Facades\Storage;

Route::post('/upload', function (Request $request) {
    $file = $request->file('file');

    if ($file) {
        $key = Config::get('app.file_key'); // Base64 encoded key stored in .env
        $key = str_replace('base64:', '', $key);
        $key = base64_decode($key);
        $encrypted = new Encrypter($key, Config::get('app.cipher'));

        $path = 'my-file.enc';
        $tempFilePath = storage_path('app/public/temp');
        $chunkSize = 1024 * 1024; // 1 MB

        $fpSource = fopen($file->path(), 'rb');
        $fpDest = fopen($tempFilePath, 'wb');

        $firstChunkEnc = null;
        while (!feof($fpSource)) {
            $plaintext = fread($fpSource, $chunkSize);
            $encryptedChunk = $encrypted->encrypt($plaintext);
            $firstChunkEnc = $firstChunkEnc ?? $encryptedChunk;
            fwrite($fpDest, $encryptedChunk);
        }

        fclose($fpSource);
        fclose($fpDest);

        if ($hasUploaded) {
            return response()->json(['success' => true, 'message' => 'File uploaded and encrypted successfully']);
        }
    }

    return response()->json(['success' => false, 'message' => 'File not uploaded']);
})->name('upload');

Decryption:

Route::get('/decrypt/{file_name}', function ($file_name) {
    $key = Config::get('app.file_key');
    $key = str_replace('base64:', '', $key);
    $key = base64_decode($key);
    $encrypted = new Encrypter($key, Config::get('app.cipher'));

    $sourceFilePath = storage_path("app/public/$file_name");
    $destinationFilePath = storage_path("app/public/decrypted-$file_name");

    $chunkSize = 1024 * 1024; // 1 MB

    $fpEncrypted = fopen($sourceFilePath, 'rb');
    $fpDest = fopen($destinationFilePath, 'wb');

    while (!feof($fpEncrypted)) {
        $encryptedChunk = fread($fpEncrypted, $chunkSize);
        $decryptedChunk = $encrypted->decrypt($encryptedChunk);
        fwrite($fpDest, $decryptedChunk);
    }

    fclose($fpEncrypted);
    fclose($fpDest);

    return response()->download($destinationFilePath, 'decrypted-' . $file_name);
})->name('decrypt');

Error

I'm encountering the following error when trying to decrypt a chunk:

Illuminate\Contracts\Encryption\DecryptException: The payload is invalid.

Question:

How can I properly encrypt and decrypt large files in chunks using Laravel's Encrypter class?