Re: [SMS D-Bus 02/19] sms: introduce message ID API

Hi Inaky, >> The current message id is 32 bits. Why are we stopping at 16? We could >> go all the way to 64 if needed... > > Well, at the end what gets sent to the network is 16 bits right? So I think we're all confused here. This ID is not being sent to the network. It is only used for uniquely identifying the message over D-Bus and to message history. This number can be as small or as big as we want.

>> Also, we need to take time and some random value into account. Perhaps >> including time() output and a simple static counter into the hashing >> function would make it unique for those 'same sender, same contents >> messages' > > So then we really don't care about being able to regenerate the hash ID > from the contents? > > The design discussions we held about this involved being able to, with > the content of the message and destination number, generating a hash > that could be uniquely reproduced by rehashing it again. You had a > reason for it and I can't remember which one it was -- I should have > written it down. But that brought the problem of 'somebody sending the > same message to the same number' which yields the same ID. > > However, if to fix that we are adding randomness in the form of time(), > why bother with the contents? let's just do a random ID from the ground > up and save us the pain of hashing. > I don't remember this discussion any more. There might be a case where an old message is re-delivered because oFono crashed after delivery but before deletion. At least to me it seems that generating a random int is really not guaranteed to be unique over reboots. Hashing seems way better. However, I'm not a math/crypto geek, so feel free to prove me wrong.