7 ms·

Just wanted to say hi – I’m one of the co-founders of this effort and would love to answer any questions or discuss further. Also wanted to add, since this is

Just wanted to say hi – I’m one of the co-founders of this effort and would love to answer any questions or discuss further. Also wanted to add, since this is a common question: does PGPP protect all identifiers or just some? As with most privacy systems, just some. Our aim is twofold: 1) to decouple a user's human identity from their network identities (mobile and Internet) and 2) randomize their network identities. We view decoupling as pretty fundamental to practical privacy -- to decouple who you are from what you do. Who you are in the context of the network is your human identity, often associated with the main point of contact you have with the network and billing -- your subscription and SIM, your broadband connection and its IP address and your home address, etc. That information has been used as the key upon which datasets can be attached. The goal then is to decouple across entities -- the different parties who have data -- and across uses -- the different mechanisms of a network protocol, such as authentication and connectivity. Other identifiers such as hardware identifiers aren't inherently attached to a person and aren't always used by networks, but even when they are, removing them is insufficient -- as our colleagues at UCSD found in recent work, phones can be identified at the PHY, without even using a unique hardware identifier.

sneak 4y ago
Does this also randomize the IMEI, or just the IMSI? Seems like if the same IMEI shows up over and over again with a different rotating IMSI then the jig is up.
- barathr 4y ago
  The IMSI. We don't do anything with the IMEI ourselves (it's in the category of hardware identifiers that I'm mentioning above). Some phones can change them when rooted, some can't. The network attach process doesn't use the IMEI inherently by spec, but some cell cores can query for it (for example, to block stolen phones). It's not a network identifier, and strange things sometimes happen with the IMEI that don't even affect connectivity -- https://www.androidauthority.com/duplicate-imei-vivo-india-1126928/ https://www.androidauthority.com/duplicate-imei-vivo-india-1...
  - jsmith45 4y ago
    Which means that the tower owners that PGPP partners with could absolutely still track users based on the IMEI if they configure their equipment to always ask for it. (It won't work in some edge cases like duplicate IMEIs but those are not super common). They may not be doing it right now, but if this sort of thing catches on, it is likely that they will start trying to do it.
  - sneak 4y ago
    > The network attach process doesn't use the IMEI inherently by spec, but some cell cores can query for it (for example, to block stolen phones). How widespread is this practice? Do the major US carriers know my IMEI? I tend to believe that they do from what I've seen in their web interfaces, and that IMSI rotation alone is basically pointless from a privacy standpoint.
    - barathr 4y ago
      This is one of the problems with mobile -- there's isn't any one universally correct answer to this (or most questions), so I'll answer to the best of my knowledge. IMSIs are what are associated with your identity (because it's your SIM and service) in a normal mobile plan, and it's what was (is?) used by carriers when they aggregate / analyze / sell location data. IMEIs can be queried by a network core (not the tower) and US carriers probably do this every once in a while to check against their stolen phone database. It can be changed on some devices but not others. It's not inherently tied to you as a person but of course it is tied to that device. For those who don't need mobile data service of any sort, I think that PGPP Relay does what's needed -- decouples your IP from your identity -- and you can use WiFi networks without revealing anything.
      - sneak 4y ago
        > IMEIs can be queried by a network core (not the tower) and US carriers probably do this every once in a while to check against their stolen phone database. It can be changed on some devices but not others. It's not inherently tied to you as a person but of course it is tied to that device. It's also linked to the rotating IMSI, so all of the rotating IMSIs that are used at the times the IMEI is interrogated are linked together from a metadata standpoint. They're also all linked to every other IMSI that was ever used with that IMEI (at the times the IMEI is interrogated). > US carriers probably do this every once in a while to check against their stolen phone database Hourly? Daily? Monthly? Only on first-time seeing a new IMSI?
nibbleshifter 4y ago
What payment methods are available, and what data do you collect for billing? Could I pick up an eSIM compatible Android tomorrow for cash at the local pawn shop, and get service using your system without handing over anything identifiable?
- barathr 4y ago
  Right now we use Stripe (mostly because it's the the most rock solid choice for payments) -- we don't ask for name or email, though of course Stripe could know that as a card processor. But our approach goes back to decoupling human identity from network identity -- what that payment says is that the holder of that card is a subscriber of the service but not, for example, what network ID you got.
  - unknownaccount 4y ago
    Why not accept cryptocurrency?
  - NoImmatureAdHom 4y ago
    Thanks for working on this, I can't wait to give you my money. It seems like you're misreading a key market segment if you don't offer cryptocurrency payments (particularly Monero).
  - sneak 4y ago
    Your somewhat evasive answers don't really instill confidence. The answer is no, you cannot. Payment cards are PII.
    - barathr 4y ago
      I don't see what was evasive, happy to answer in more detail if there's something you're seeing not answered above. We use Stripe as a credit card processor -- so we have what Stripe's (very well documented) APIs provide. That reveals that you purchased the service, but we don't know anything about the network identity you have nor your Internet usage, because architecturally we don't have that information. I understand that revealing that information to Stripe may not be acceptable -- not sure what to say to that. We've gotten requests for other forms of payments and we can consider it, but we don't support anything other than credit cards at the moment. (There are credit cards that aren't linked to a person, if that's a better option.)
throwaway81523 4y ago
Um what? Is PRZ involved? Is he ok with your using that name? He had something called PGPFone a long time ago, though it didn't get much traction. There have also been tons of other encrypted voice programs. Obscuring traffic patterns without stupendous amounts of dummy traffic is quite difficult. That someone is connected to your network at all is already a huge giveaway. I have trouble seeing how something like this can work without a very big operator (think Cloudflare or AWS) being involved, and anything that size would have to get in bed with regulators. It's a lot easier if you're only trying to do low bandwidth text.
- mrex 4y ago
  >He had something called PGPFone a long time ago, though it didn't get much traction. Does anyone have a copy of it? I can't find it ANYWHERE. Actually used it way back when, it worked surprisingly OK and was the first softphone I used.
  - mackatsol 4y ago
    Here you go: http://www.pgpi.didisoft.com/products/pgpfone/ http://www.pgpi.didisoft.com/products/pgpfone/
    - Archaea 4y ago
      Looks like the only downloadable on that mirror is the manual.
codethief 4y ago
Hi barathr, thanks for joining the discussion! Having had a brief look at your paper and the Usenix slides[0], I've got three questions: - Given that your Android app is security-critical for its users, are you planning on open-sourcing it in the near future? - How exactly does your app work on Android? How does it rotate the IMSI? (I don't know a lot about eSIMs but I would have thought a regular app can't easily change the carrier/network settings.) - As for the relay functionality, I suppose on Android this "simply" sets up a VPN once the network connection is established? [0]: https://www.usenix.org/conference/usenixsecurity21/presentation/schmitt https://www.usenix.org/conference/usenixsecurity21/presentat...
octoberfranklin 4y ago
Hi, less than 48 hours ago you had a "Show HN". Your claim "we don't learn which eSIM your phone gets" is false. The eSIM update protocol, which is implemented in firmware which you do not control, will send you (the carrier) the eSIM's permanent ID (the EID), and you can't stop this. https://news.ycombinator.com/item?id=32416373 https://news.ycombinator.com/item?id=32416373 Moreover, you provide no protection whatsoever against IMEI tracking, which all carriers implement. IMEIs are reported to the carrier immediately after authentication/attach (AKA), and many will block invalid/unexpected IMEIs. You can't prevent this. Without a solution to IMEI tracking your work on IMSI tracking isn't much use. This won't protect anybody from the telcos. At best it might stop people using a stingray without assistance from the telco (i.e. almost nobody). https://news.ycombinator.com/item?id=32416308 https://news.ycombinator.com/item?id=32416308

sneak 4y ago

Does this also randomize the IMEI, or just the IMSI? Seems like if the same IMEI shows up over and over again with a different rotating IMSI then the jig is up.

barathr 4y ago
The IMSI. We don't do anything with the IMEI ourselves (it's in the category of hardware identifiers that I'm mentioning above). Some phones can change them when rooted, some can't. The network attach process doesn't use the IMEI inherently by spec, but some cell cores can query for it (for example, to block stolen phones). It's not a network identifier, and strange things sometimes happen with the IMEI that don't even affect connectivity -- https://www.androidauthority.com/duplicate-imei-vivo-india-1126928/ https://www.androidauthority.com/duplicate-imei-vivo-india-1...
- jsmith45 4y ago
  Which means that the tower owners that PGPP partners with could absolutely still track users based on the IMEI if they configure their equipment to always ask for it. (It won't work in some edge cases like duplicate IMEIs but those are not super common). They may not be doing it right now, but if this sort of thing catches on, it is likely that they will start trying to do it.
- sneak 4y ago
  > The network attach process doesn't use the IMEI inherently by spec, but some cell cores can query for it (for example, to block stolen phones). How widespread is this practice? Do the major US carriers know my IMEI? I tend to believe that they do from what I've seen in their web interfaces, and that IMSI rotation alone is basically pointless from a privacy standpoint.
  - barathr 4y ago
    This is one of the problems with mobile -- there's isn't any one universally correct answer to this (or most questions), so I'll answer to the best of my knowledge. IMSIs are what are associated with your identity (because it's your SIM and service) in a normal mobile plan, and it's what was (is?) used by carriers when they aggregate / analyze / sell location data. IMEIs can be queried by a network core (not the tower) and US carriers probably do this every once in a while to check against their stolen phone database. It can be changed on some devices but not others. It's not inherently tied to you as a person but of course it is tied to that device. For those who don't need mobile data service of any sort, I think that PGPP Relay does what's needed -- decouples your IP from your identity -- and you can use WiFi networks without revealing anything.
    - sneak 4y ago
      > IMEIs can be queried by a network core (not the tower) and US carriers probably do this every once in a while to check against their stolen phone database. It can be changed on some devices but not others. It's not inherently tied to you as a person but of course it is tied to that device. It's also linked to the rotating IMSI, so all of the rotating IMSIs that are used at the times the IMEI is interrogated are linked together from a metadata standpoint. They're also all linked to every other IMSI that was ever used with that IMEI (at the times the IMEI is interrogated). > US carriers probably do this every once in a while to check against their stolen phone database Hourly? Daily? Monthly? Only on first-time seeing a new IMSI?

nibbleshifter 4y ago

What payment methods are available, and what data do you collect for billing? Could I pick up an eSIM compatible Android tomorrow for cash at the local pawn shop, and get service using your system without handing over anything identifiable?

barathr 4y ago
Right now we use Stripe (mostly because it's the the most rock solid choice for payments) -- we don't ask for name or email, though of course Stripe could know that as a card processor. But our approach goes back to decoupling human identity from network identity -- what that payment says is that the holder of that card is a subscriber of the service but not, for example, what network ID you got.
- unknownaccount 4y ago
  Why not accept cryptocurrency?
- NoImmatureAdHom 4y ago
  Thanks for working on this, I can't wait to give you my money. It seems like you're misreading a key market segment if you don't offer cryptocurrency payments (particularly Monero).
- sneak 4y ago
  Your somewhat evasive answers don't really instill confidence. The answer is no, you cannot. Payment cards are PII.
  - barathr 4y ago
    I don't see what was evasive, happy to answer in more detail if there's something you're seeing not answered above. We use Stripe as a credit card processor -- so we have what Stripe's (very well documented) APIs provide. That reveals that you purchased the service, but we don't know anything about the network identity you have nor your Internet usage, because architecturally we don't have that information. I understand that revealing that information to Stripe may not be acceptable -- not sure what to say to that. We've gotten requests for other forms of payments and we can consider it, but we don't support anything other than credit cards at the moment. (There are credit cards that aren't linked to a person, if that's a better option.)

throwaway81523 4y ago

Um what? Is PRZ involved? Is he ok with your using that name? He had something called PGPFone a long time ago, though it didn't get much traction. There have also been tons of other encrypted voice programs. Obscuring traffic patterns without stupendous amounts of dummy traffic is quite difficult. That someone is connected to your network at all is already a huge giveaway. I have trouble seeing how something like this can work without a very big operator (think Cloudflare or AWS) being involved, and anything that size would have to get in bed with regulators. It's a lot easier if you're only trying to do low bandwidth text.

mrex 4y ago
>He had something called PGPFone a long time ago, though it didn't get much traction. Does anyone have a copy of it? I can't find it ANYWHERE. Actually used it way back when, it worked surprisingly OK and was the first softphone I used.
- mackatsol 4y ago
  Here you go: http://www.pgpi.didisoft.com/products/pgpfone/ http://www.pgpi.didisoft.com/products/pgpfone/
  - Archaea 4y ago
    Looks like the only downloadable on that mirror is the manual.

codethief 4y ago

Hi barathr, thanks for joining the discussion! Having had a brief look at your paper and the Usenix slides[0], I've got three questions: - Given that your Android app is security-critical for its users, are you planning on open-sourcing it in the near future? - How exactly does your app work on Android? How does it rotate the IMSI? (I don't know a lot about eSIMs but I would have thought a regular app can't easily change the carrier/network settings.) - As for the relay functionality, I suppose on Android this "simply" sets up a VPN once the network connection is established? [0]: https://www.usenix.org/conference/usenixsecurity21/presentation/schmitt https://www.usenix.org/conference/usenixsecurity21/presentat...

octoberfranklin 4y ago

Hi, less than 48 hours ago you had a "Show HN". Your claim "we don't learn which eSIM your phone gets" is false. The eSIM update protocol, which is implemented in firmware which you do not control, will send you (the carrier) the eSIM's permanent ID (the EID), and you can't stop this. https://news.ycombinator.com/item?id=32416373 https://news.ycombinator.com/item?id=32416373 Moreover, you provide no protection whatsoever against IMEI tracking, which all carriers implement. IMEIs are reported to the carrier immediately after authentication/attach (AKA), and many will block invalid/unexpected IMEIs. You can't prevent this. Without a solution to IMEI tracking your work on IMSI tracking isn't much use. This won't protect anybody from the telcos. At best it might stop people using a stingray without assistance from the telco (i.e. almost nobody). https://news.ycombinator.com/item?id=32416308 https://news.ycombinator.com/item?id=32416308