From the course: Symmetric Cryptography Essential Training
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The RC4 stream cipher
From the course: Symmetric Cryptography Essential Training
The RC4 stream cipher
- [Instructor] Now we'll turn our attention to the RC4 Stream Cipher. This Stream Cipher was a proprietary algorithm that was originally designed in 1987 by Ron Rivest of RSA Security, but it was leaked to the public in 1994. The RC4 just stands for "Ron's Code 4", or "Rivest Cipher 4" depending on who you ask. I use it here as an example because it's very simple, and it's easy to implement in software. It's also not an LFSR. Unfortunately, there are several concerning vulnerabilities that I won't cover here. This means that you shouldn't use the original version of RC4 if you need a secure Stream Cipher. RC4's keystream is generated in Output Feedback mode, so this makes it independent from the plaintext. It has a very simple structure, including one eight by eight S-box. RC4 needs some initial setup. The first step is to set up the S-box based on the key that is being used. The next steps are to set the counter variables "i" and "j" both to zero. With these five steps, a single…
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