What is protected division? (in reference to genetic programming and cryptography)

Question

I am getting references in a paper on genetic programming, to a "protected division" operation. When I google this, i get mostly papers on genetic programming and various results related to cryptography, but none that explain what it actually is. Does anybody know?

Answer 1

Protected division (often notated with %) checks to see if its second argument is 0. If so, % typically returns the value 1 (regardless of the value of the first argument).

http://en.wikipedia.org/wiki/Genetic_programming

In cryptography it doesn't seem to be well-defined, but the top google hit is for protecting against side channel attacks (in that case, via power use - you can guess what numbers are being used in the division by looking at the power consumption of the hardware doing the encryption) http://dl.acm.org/citation.cfm?id=1250996 http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.9.7298&rep=rep1&type=pdf

Answer 2

In GP protected division is a modified division operator which does not signal "division by zero" error when denominator is 0 (zero). It typically returns 1 when denominator is zero.

Answer 3

It divides on threshold function of argument instead of argument.

Thres(x) = epsilon*Theta(x) if fabs(x)<epsilon.

Where Theta() is non-zero variant of theta-function.

Other threshold functions possible. Or sometimes it is just 'epsilon'.