Looking Out To Sea

During the week a friend from work pointed me towards the Cyber Security Challenge, which is being touted as a popular method to promote the field of computer security in the UK.

They had released a teaser challenge as a sample of the main competition which seemed like it was worth trying. It took us a couple of days to get to the answer, not least of all because we actually had work to do!

Since the teaser challenge is now well over and the “official” method has been published on the challenge page (move your mouse over the big white space to see the solution) I thought it would be interesting to go through my solution and see (a) what the puzzle-setters had done (b) how the answer was stumbled upon (c) how the answer could have been derived and (d) where my method differed from the official approach, despite reaching basically the same answer. It’s been a while since I thought about the practical techniques of cryptanalysis so my methods are neither the best nor the most sensible, but at least I can be honest. Helen’s just finished reading Cryptonomicon so will probably tell where I went wrong!

If you want to try out your skills the original problem is still available and will probably be there for some time. At least you can see what the starting point was.

I’ll write up my results and methods in the next few days, posting each section as it goes. I’ll also publish the code I used to extract the solution, which was written in Haskell. I’ve never done anything like this before but the Haskell list-munging functions and point-free style made it simple. The effortless compositional style of creating pipelines of functions meant that I could play with little sections, joining and splicing them as necessary, until I found something which seemed like a good result. But there will be more details in the coming days.