It is quite easy to time for yourself. Try timing it many times with a sig_bytes off by one(only one character changed). Then compare that with the correct on

It is quite easy to time for yourself. Try timing it many times with a sig_bytes off by one(only one character changed). Then compare that with the correct one. You'll notice the (small) difference. There are no tests for it in the keyczar that I could find. I doubt they tested it. The reasons are many... but this is python, so each operation is much more complicated than C/asm. There are lots of branches, memory usage and cache effects - so code is much more input dependant - especially the integer ops used here. Take a look at this code to see one of the reasons why this python code has variable timing depending on input(like most code does). x,y = 3,3 id(x) == id(y) # python shares ints in different variables