HC-256: A Fast and Secure Software Stream Cipher
Why should you just learn about the most common methods? As a researcher, you should never fully dismiss any method, as methods that might not be popular now may come back and be ready to take on new challenges. Also, a method will have been created for a purpose, and reading the paper will show how the authors have addressed the challenge. It’s basically a journey of discovery and will typically add your knowledge.
And, so, I’ve been reading this paper [here]:
The HC-256 method was created in 2004, and uses a 256-bit key (K) and a 256-bit nonce (IV) value. Internally it has two secret tables: P and Q, and where each table has 1,024 32-bit words. Basically, these represent state values, and each change of state will update one of the entries of the table, and which uses a non-linear update function. Thus, after 2,048 state changes, every element of the tables will have been updated. We then derive the final has by taking a SHA-256, but where we use the P and Q tables as S-boxes. Overall, it is a fast-stream cipher with just four CPU cycles per byte.
The basic functions that HC-256 uses are simple and involve either EX-OR, mod, add or bit shift…
