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.