I somewhat need to decrypt data being sent from a nike+ sport kit to an iphone. The data uses a hash function I beleive and I need some help.
The data has a 'key' hex value that rolls from 160 to 175 in decimal, and the data that follows is some indication of duration of a footstep, from which the speed is inferred.
170-111-247-81-180-253-225-159 - Data. Last value likely some sort of checksum.
I am sure it uses a hash function since when I keep the transmitter still on a table, it transmits the same pattern for every 'key', however, sometimes after vigerous movement the pattern will change the latter half or completely. I would be fine for now if I could figure out the difference between moving and not, but I cannot really. I am going to gather all the strings for what I deem to be standstill data and see if there is a finite number of them and/or if they are evenly distributed.
Pointers as to how to solve this would be greatly appreciated. Someone suggested looking in the iOS kernel for the appropriate extention, but I think that is out of my depth. If anyone can flat out solve it within a day or two I will happily pay £10. If it was really obvious I may guilt trip
I expected that the data sent would be the integral of the displacement of the cone magnet in the transmitter. However, this would always yeild a zero when not moving and hence the same string, so perhaps not.
Sample data for one cycle (if that means anything):
I know my 'string' terminology wasn't correct.. But I am not good with these things.