“When you connect to the network, you offer an IMSI number to show the background database that you are a paying user, and here are the services you have subscribed to,” says Schmitt. “The system then notifies the rest of the kernel to give you access to the network. But what we do with PGPP changes the bill. The subscriber database can confirm that you are a paying user without knowing who you are. We have separated and changed the billing and authentication. ”
Reprocessing some billing systems and distributing the application to users would be far easier for carriers than a deeper overhaul of the network. Raghavan and Schmitt are in the process of turning their research into a startup to facilitate project promotion among United States telecommunications. They acknowledge that even with the ease of adoption, it is still a long way off that the entire industry will soon switch to PGPP. But getting just a few carriers, they say, could still make a big difference. This is because mass location data becomes much less reliable if any significant portion of the total set is soiled. If 9 million Boost Mobile subscribers, for example, were required to broadcast identical or random IMSI numbers, which would impair the accuracy and usefulness of the entire data set.
The fact that small, virtual service providers that don’t even manage their own cell towers – known as MVNOs – were able to implement this scheme on their own is significant, says cryptographer Bruce Schneier, who first learned about PGPP in January and recently became a project consultant. .
“One carrier can do it alone without anyone’s permission and without anyone else changing anything,” says Schneier. “I can imagine one of these smaller companies saying it would offer that as added value because they want to be different. This is privacy at a very small cost. That’s a neat thing. ”
In a competitive, monolithic wireless market, privacy could be attractive as a marketing tactic. It is possible that the big three carriers would try to block MVNOs from adopting something like PGPP through contractual moratoriums. But researchers say some MVNOs have expressed interest in the proposal.
Between potential pressure from the police and loss of access to data – plus the need to distribute the application or turn on mobile operating systems – carriers could have little incentive to adopt the PGPP. To the extent that law enforcement could oppose such a scheme, Schmitt notes that it would still be possible for carriers to perform a targeted location history search for specific telephone numbers. Researchers say they believe access would be legal in the U.S. under the Communications Enforcement Assistance Act. This is because one warning of PGPP is that it only adds privacy protection to cell tower interactions that involve data networks like 4G or 5G. It does not attempt to cooperate with historical telephony protocols that allow traditional telephone calls and SMS text messages. Users would have to rely on VoIP calls and messaging based on data for maximum privacy.
The approach also focuses on IMSI numbers, along with their 5G counterparts known as persistent subscription identifiers or SUPIs, and does not protect or block static hardware identifiers such as International Mobile Identity Identity (IMEI) numbers or media access control (MAC) addresses. They are not used in cell tower interactions that researchers are trying to anonymize, but could provide other ways to track.
Having a simple and clear option to address one large exposure to location data remains significant, after years of data misuse and growing privacy concerns.
“Honestly, now I have a feeling we haven’t seen it before?” Raghavan says. ‘No,’ Wow, this was so hard to figure out. ‘ It is obviously retrospective. ”
“That’s why we felt better as system researchers,” Schmitt adds. “In the end, the simpler the system, the better.”
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