[Cryptography] Re: Burner phone == One Time (i)Pad

[Arnold Reinhold]

On Thu, 19 Nov 2015 Henry Baker wrote:

> Anyone who's watched a recent movie or TV show knows about burner phones.  They seem to have become the 21st century version of a "one time pad".
> 
> What's the most important criterion for a burner phone?  It should be *cheap*; only the most well-heeled terrorists would use an iPhone as a burner.
> 
> There's much less need to encrypt a burner phone.  In fact, one might purposely put false/misleading information onto such a phone prior to throwing it away.  (And *delete* it, just to piss off Mr. Vance, who hates cellphone software that actually deletes data when you press "delete".)
> 
> "investigators were able to access the data on the phone, including a detailed map of the concert hall and an SMS messaging saying �we�re off; we�re starting.�  Police were also able to trace the phone�s movements."
> 
> "Ironically, the suspects were overheard discussing the need to frequently swap out their cellphones.”

Searching for potential terrorists is a needle in a hay stack problem. Anything that narrows that search potentially helps the good guys. Presumably they can get lists of the IMSIs for all prepaid phones from the manufacturers and give their traffic special attention. It’s not hard to imagine patterns of suspicious behavior that could be easily detected, phones that go dark after a short interval of use, for example. It two such phones called each other, that would be a huge red flag and gain priority handling. Remember all cell phone that are powered on (and maybe some that aren’t) are tracked by the cell towers and that location data is saved. If a terrorist cell switches phones all at the same time, that pattern should be easy to pick up. But if they don’t, new phones can be linked to older ones in the network. And if anyone in the group foolishly carries a burner and real phone together, it would not be hard to link them. 

Given the NSA  thoroughness revealed in the Snowden document, I would be very surprised if they don’t have a whole department devoted to tracking burner phones. Yes, some will turnout to be innocent uses like battered women shelters or people with limited income, but those will not be hard to separate out. 

Arnold Reinhold