RC4 (also known as Rivest Cipher 4) is a form of stream cipher. It encrypts messages one byte at a time via an algorithm.

Plenty of stream ciphers exist, but RC4 is among the most popular. It's simple to apply, and it works quickly, even on very large pieces of data. If you've ever used an application like TSL (transport layer security) or SSL (secure socket layer), you've probably encountered RC4 encryption. 

But you may not know how it works.

We'll take a high-level approach and explain what the Rivest Cipher is in terms anyone can understand. We'll also explain why it's helpful, and we'll point out a few known limitations.

What is a Rivest Cipher? 

In 1987, a man named Ron Rivest developed the RC4 encryption method. He intended to keep the rules of the cipher secret, and if his plan had worked, he would have created one of the safest tools anyone could use to protect information. Unfortunately, his plans didn't succeed. 

In 1994, an anonymous person posted an intricate description of the cipher's rules in a public space. Now that RC4's rules are out in the open, we know much more about how it works. Unfortunately, that means hackers know a lot more about how to break it too. 

RC4 relies on:

• Key inputs. This tool generates an eight-bit number (cipher) that's impossible to guess. 
• Keystreams. The cipher scrambles plain text. 
• Product. An X-OR operation combines the keystream with the cipher. 

Developers continue to build on and improve RC4 encryption. They hope to minimize hacking risks, although experts say hackers can still get through. New versions include RC4A, VMPC, and SPRITZ. All are more complex and