Question

So I’m reading this book on an introduction to cryptography, there’s this exercise about reading a message from a paper and you’d have to use a cosine function to find out how many letters each strip of paper should have (once you tear it, so you could decode the message).

I mean really? Will there be a similar scenario to this? whats the use? Or are there other applications of trigonometry in cryptography?

Answer 1

Any function/method that implements the properties of diffusion and confusion (cit. Shannon) is eligible to be used for cryptographic purpose

However, diffusion and confusion are relative to the computational power of the system in which the algorithm will run. For the average guy with paper&pencil trigonometric functions will suffice, for modern CPUs more complicated math should be used (factorization of large numbers, inversion of discrete logarithms, math over elliptic curve etc..)