iphone - Is it possible to have a single trial per device? -

is possible provide service in 1 free trial given each device without possibility of individual being able multiple free trials on single device. if impossible, know of way of making difficult obtain multiple free trials.

you can generate license key based on device's unique id, request date, , own private key create license valid date.

you application verify license key valid decoding license key public key, , comparing expiration date , device id. people can't forge bogus request, since license key valid prescribed date , given device id.

(hint: read public-key cryptography)

however, it's not totally foolproof. determined attacker can root device, , install custom firmware allows him control identifier returned "getdeviceid()". isn't people willing do, people rather find alternative free app or buy app rather going through route. against crackers sort of determination , skills, there not can about.

alternative avenue of attack replace public key ship application attacker's private/public key combination, , can potentially write key generator can generate license key forged application. can make attack difficult self-verification of own executable.

however, no security scheme foolproof, java/android application can reverse engineered , determined hacker can forge application , disable license checks. foolproof way prevent unauthorized usage of application not distribute application @ all.