From the course: Symmetric Cryptography Essential Training

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The RC4 stream cipher

The RC4 stream cipher

From the course: Symmetric Cryptography Essential Training

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The RC4 stream cipher

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- [Instructor] Now we'll turn our attention briefly to the RC4 Stream Cipher. This stream cipher was a proprietary algorithm that was originally designed in 1987 by Ron Rivest at 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, which tends to be harder to implement in software. 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 key stream is generated in output feedback mode, OFB, which we covered in a few videos, so this makes it independent from the plaintext. It has a very simple structure, made up mainly of one 256-byte array to store the state. RC4 needs some initial setup. The first step is to set up the internal state based on the key that…

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