The Code Book – is a short history of mankind’s journey to be able to transmit messages secretly. Its a very well researched compilation of what were the pre-cursors to the modern technology field that we call as encryptology.
I found some of the examples really interesting:
- Amongst the first ways to send coded messages via a messenger through non-friendly territory was the means of writing the message on the messenger’s scalp. The king would choose a messenger,shave the guys head, write a message with a special ink and wait for the hair to grow back again. The messenger would then pass through the enemy territory and even if searched, no one would probably guess that the message is on the scalp. The messenger would again get shaved at the other king’s court so that the recipient king could read the message. Very intuitive but I guess once the word spread, most travellers would have been shaved as part of their search
- The Roman period saw a very advanced cryptology technique – simple to code and very tough to decode. The Romans would have a special septre on which a narrow strip would be rolled and the message would be written. When the strip is unwound and read vertically, its completely gibberish. The only way to read this was to roll the strip back again on a cylinder of the same diameter. This was taken a step further and the woodden staff used was not a simple cylinder but a tapering one, which added to the complexity of someone trying to break the code using brute force.
Simon Singh highlights that the history of genuine code-breaking has been based on a simple premise – find patterns in the code and break the problem into smaller parts.
On the other hand, to make a good code, one should
- Avoid putting a condition as it reduces the number of possibilities
- Aspire for a multi-stage cipher where the subsequent stages lose the path from the previous ones