Cracking nike+ code
Hi,

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 :P.

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):

160-253-227-217-93-140-88-135
161-179-231-25-206-107-246-177
162-6-25-152-0-22-174-147
163-35-178-210-132-98-5-12
164-172-175-158-237-159-188-194
165-69-2-38-237-164-162-3
166-74-212-31-86-240-206-22
167-28-46-121-77-29-15-159
168-161-112-226-109-55-253-210
169-120-75-225-195-25-72-170
170-111-247-81-68-141-145-47
171-55-85-11-54-200-186-170
172-196-21-176-9-246-115-106
173-87-42-162-64-243-125-1
174-239-170-68-89-173-231-28
175-43-60-37-36-188-137-195

I know my 'string' terminology wasn't correct.. But I am not good with these things.

Jo