Cycle-walking is a technique for format-preserving encryption that involves repeating an encryption process until the result is inside a desired range.
For example, given an input P, a range R, and an encryption function E.
C := E(P)
Is C in R?
yes?
Output C and quit
no?
C := E(C)
Try again
My question is, does the variable timing of this pose a threat? It isn't constant time, but the time is dependant on E(P)
, which in theory shouldn't be a problem.