&gt; With this (and your computer) you can secure a message with a password in a way that&#x27;s unbreakable. I can&#x27;t break it, your government can&#x27;t break it, other people&#x27;s governments can&#x27;t break it. Secure.<p>Argh. No.<p>&gt; Should you use it? No. There&#x27;s many important missing features that are present in proper symmetric encryption tools, such as proper key derivation, protection against modification, IVs, and fewer bugs.<p>This (buried) warning makes these things sound like bells and whistles. The truth is they&#x27;re essential to security.<p>Here are some good reasons not to use this for anything:<p>1. It conflates passwords with keys. Users will not choose high-entropy passwords when left to their own devices.<p>2. It doesn&#x27;t take an IV. This means a given password will always generate the same key stream, which means password reuse will lead to plaintext recovery by simple statistical methods. There are no warnings about this.<p>3. It&#x27;s not authenticated. An attacker can modify messages in flight with unexpected consequences that very often include plaintext recovery.<p>4. RC4 is irreparably broken. Dropping 1024 bytes from the key stream might help in the author&#x27;s intended use-case (assuming users adhere to it), but this is not an effective mitigation in general. The best attacks on RC4 rely on periodic biases that persist over the entire key stream.