In J. E. Littlewood's, "A Mathematicians Miscellany" there is the following passage about ciphers. I found it interesting for a couple of reasons.
First of all the "legend that every cipher is breakable" is something that is certainly not a common belief nowadays and it makes me wonder why it was back then.
Secondly I have no knowledge of cryptography and I would be very interested in hearing from someone more specialized what are the weak points of Littlewood's proposed cipher (I guess it cannot hold up to modern standards)
In particular his claim that a single message cannot be unscrambled "even if all were known except the key number $N$" is it true with modern computing power ?
Best Answer
Littlewood's cypher is a one-time-pad, which would be unbreakable if fed by a true random number generator, but Littlewood's pseudo-random number generator is broken. See Breaking Littlewood's cypher by Damien Stehlé (2003).