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

[Denis Kenzior <denkenz@gmail.com>]

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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.

Regards,
-Denis