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Comment by Scoundreller | Hacker News Reader

So, I’m currently in North America but with a foreign SIM, so I have that country’s IP, most ads are in a language I can’t understand, and McDonalds app won’t let me login unless I switch to wifi with a local IP.

This is all great, but does this mean that the local provider has no access to my traffic? I guess DNS is all resolved overseas too? How does the tunnelling work?

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That tunneling is created generally for billing and metering purposes (for telco's benefit). A lot of cooperation between carriers happen in order to create that tunnel. Don't assume it's an encrypted tunnel.

The tunnels between carriers could be encrypted. They don't _have_ to be. The LTE S1 link (eNodeB <-> packet core) may not be.

Like, if your eNB is a picocell or feeding a DAS, it probably is doing backhaul over IPSec over internet or dedicated circuit, but if it's normal carrier network, likely not.

ref Page 37 of https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.S...

The network you're on has theoretical full access to everything. If the network is hostile you're screwed, because even with the improved protection in 4G/5G they can still easily force a downgrade attack.

This really depends on what you mean by "my traffic"; keeping in mind that your local provider is the ultimate man-in-the-middle.

I guess that’s a part of the question: is my phone encrypting (with whatever gsm standard) to the overseas provider and the local provider can’t really see anything, or does it go to the local provider in the clear and they tunnel it over to the overseas provider?

My understanding is that the A5/1 (GSM) encryption is applied to the communication between the device and the local service provider. The local service provider then decrypts and routes the packets.

Where local service provider is just the tower.

https://www.firstnet.com/power-of-firstnet/firstnet-advantag...

>FirstNet is designed with a defense-in-depth security strategy that goes well beyond standard commercial network security measures, providing protection without sacrificing usability. And now, we’ve gone farther than anyone in the industry to secure public safety communications. FirstNet will be the first-ever network with comprehensive, tower-to-core encryption based on open industry standards.

Which implies every other network doesn't encrypt that traffic (or does it with some proprietary scheme... which wouldn't give me a lot of confidence)

Telcos rarely do end-to-ends, usually they handle signaling out of band, strip headers, decipher payload and re-cipher with new session information each time your data switches medium. In-band signaling with E2E and recursive encapsulations like TLS over TCP over IP are very Internet/IP pattern.

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