To identify an RC4 algorithm, there are some key characteristics that can help you detect it rather than you having to spend hours trying to analyze each part of the algorithm:
- The generation of the 256 bytes array: This part is easy to recognize, and it's quite unique for a typical RC4 algorithm like this:
Figure 27: Array generation in the RC4 algorithm
- There's lots of swapping: If you can recognize the swapping function or code, you will find it everywhere in the RC4 algorithm. The KSA and PRGA parts of the algorithm are a good sign that it is an RC4 algorithm:
Figure 28: Swapping in the RC4 algorithm
- The actual algorithm is XOR: At the end of a loop, you will notice that this algorithm is basically a xor algorithm. All the swapping is done on the key. The only changes that affect the data are done through xor:
Figure 29: Xor operation in the RC4 algorithm
- Encryption and decryption similarity: You will also notice...
