Posted: Tue Oct 12, 2010 1:14 am Post subject: Need help understanding stream cipher
I am trying to understand how stream cipher works, but the book I am reading is in my opinion not clear enough. So I did some research on the Internet and I made a drawing of how stream cipher works but the problem is I do not know if I got it right. Can you please read the encryption and decryption process I put together and check my drawing and correct me if I am wrong?
Thanks in advance.
Stream Cipher Encryption:
1. Starts with a secret key ("seed")
2. Sender and receiver both share the secret key
3. Sender and receiver generate identical key streams using the shared key
4. The clear text message will be processed bit by bit (as a stream)
5. The key stream is then logically combined with the plain text via Exclusive-Or (XOR) which is represented by a circle with a cross in it to produce cipher text.
Stream Cipher Decryption:
1. At the other end of the network, the receiver uses the shared secret key to produce identical key stream to the sender.
2. This is then XOR-ed with the incoming cipher text to reproduce the original text.
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