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Comment by rscale | Hacker News Reader

If anybody needs true, total anonymity it's worth reading this paper before buying any cell phone: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3607247/pdf/srep...

The paper shows that 95% of cell phone subscribers are personally identifiable from VERY little spatio-temporal information.

Another issue is that an upstream vendor could easily provide the government with the phone IMEIs and SIM IMSIs that they supply to BurnerPhone, without disclosing this to BurnerPhone. This would create a pool of phones that are self-identified as high-value surveillance targets.

If I was in charge of identifying miscreants for a nasty regime, I'd also watch for SIM card changes (an IMEI whose IMSI changes on a regular basis), and I'd especially look for cliques of handsets that showed the same SIM-changing behavior. As such, I can't help but wonder if swapping SIM cards might generate unwanted attention.

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"Methods The dataset. This work was performed using an anonymized mobile phone dataset that contains call information for ,1.5 M users of a mobile phone operator. The data collection took place from April 2006 to June 2007 in a western country. Each time a user interacts with the mobile phone operator network by initiating or receiving a call or a text message, the location of the connecting antenna is recorded [Fig. 1A]. The dataset’s intrinsic spatial resolution is thus the maximal half-distance between antennas. The dataset’s intrinsic temporal resolution is one hour [Fig. 1B]."

This seems kind of sketchy to me considering how CDMA networks currently work:

http://en.wikipedia.org/wiki/Code_division_multiple_access#S...

"These systems were designed using spread spectrum because of its security and resistance to jamming. Asynchronous CDMA has some level of privacy built in because the signal is spread using a pseudo-random code; this code makes the spread spectrum signals appear random or have noise-like properties. A receiver cannot demodulate this transmission without knowledge of the pseudo-random sequence used to encode the data. CDMA is also resistant to jamming. A jamming signal only has a finite amount of power available to jam the signal. The jammer can either spread its energy over the entire bandwidth of the signal or jam only part of the entire signal."

It's likely my own ignorance, but I don't understand the concern you're raising. What's the relationship between frequency-hopping spread spectrum technology and communication/antenna records?

"Each time a user interacts with the mobile phone operator network by initiating or receiving a call or a text message, the location of the connecting antenna is recorded"

CDMA allows multiple towers to handle network traffic. Implying there's only one tower handling the traffic seems flawed to me. I could be wrong though. This was the issue I was trying to bring up.

Any number of towers might be in range of a phone, but (from my understanding) only one tower (with the strongest signal) is used by the cellphone. As the cellphone moves, it can be handed off to other towers (based on signal strength).

Multiple towers is worse than one. It allows pinpointing the user much more accurately. With three towers with signal strength and timing information you'll get exact location.

Yes, you're wrong. There's a data link from the phone to one tower when setting up a call or similar - the ID of that tower is communicated to the core network. You can handover to another tower if that signal becomes stronger (e.g. you're moving) - this'll just give you more information, i.e. the fact that the user was moving, and you can now narrow down the location further to the parts where the two cells overlap in coverage.

The spatio-temporal tracking only works if the battery is in the phone all the time. Take the battery out unless you're making a call or checking voicemail.

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