encryption - Create an encrypted zip archive with PHP

Question

I am searching for a way to encrypt a .txt file into a zip, but in a secure password protected way. My goal is to email this file to me, without anyone being able to read the content of the attachment.

Does anybody know an easy, and above all, secure way to accomplish this ? I can create zip archives, but I do not know how to encrypt them, or, how secure this is.

Answer 1

Note: this answer recommends a cryptographic method that is known insecure, even with good password. Please see link from comments and the Winzip QA on AES. Support for in-php AES zip encryption arrives with php 7.2 (and libzip 1.2.0), which means this answer will soon be outdated too. Until then see this answer for how to call out to 7z instead of the zip command, which supports winzip's AES encryption.

You can use this:

<?php echo system('zip -P pass file.zip file.txt'); ?>

Where pass is the password, and file.txt will be zipped into file.zip. This should work on Windows and Linux, you just need to get a free version of zip for Windows ( http://www.info-zip.org/Zip.html#Win32 )

This kind of security can be broken by brute force attacks, dictionary attacks and etc. But it's not that easy, specially if you chose a long and hard to guess password.