6 ms·

What features depend on the use of a phone number? Sign up and contact discovery? I don’t understand why a plaintext database is the alternative.

tptacek 4y ago
Your Signal contact list is your device's contact list, keyed by phone numbers.
- O__________O 4y ago
  For clarity, this assumes you allow Signal access to the device’s contact list, which is not required.
  - palata 4y ago
    For clarity, you allow the open source client app (which you can audit and compile yourself) to securely share your contact list with a secure enclave (which is open source so you can audit it as well).
    - O__________O 4y ago
      The client-side contact list is one of two lists: (a) device’s contact list if Signal is given access — or (b) list of numbers that have manually been add to the App and Signal is not given access to device’s contact list because user declined providing it access. Also, might be wrong, but appears Signal’s secure enclave, which is based on Intel’s SGX technology, is known to be vulnerable to side-channel attacks and Intel’s SGX code & hardware is not open source: https://medium.com/@maniacbolts/signal-increases-their-reliance-on-sgx-f46378f336d3 https://medium.com/@maniacbolts/signal-increases-their-relia...
      - palata 4y ago
        Yep, you have to trust the secure enclave for this to work!
        O__________O 4y ago
        No, you have to trust anyone with access to the server; secure enclave provides no security given it appears it is vulnerable to side channel attacks; see comment you just replied to for related link. Basically all it does is given Signal plausible deniability for public search warrants: https://signal.org/bigbrother/ https://signal.org/bigbrother/ It would do nothing to stop national security letters. Basically, you should assume the functionality provided by the secure enclave is only in name; given the NSA ATT national security letters enabled both physical access and system modifications, see no reason to believe others would not be required to do so as well: https://en.m.wikipedia.org/wiki/Room_641A https://en.m.wikipedia.org/wiki/Room_641A Again, average person does not have a threat model that makes this relevant, but to say Signal does not have access to the SGX data is purely based on trust, not mathematical proofs.
        palata 4y ago
        At that point, your phone is vulnerable. As is your computer, and your connected fridge. If your threat model does not allow it, use manual e2ee with pigeons. Otherwise, well secure enclave will get better with time, which will make Signal better too.
        O__________O 4y ago
        Signal should make threats clear to users, just as they should have notified all users that multiple 3rd parties downloaded all the phone numbers in Signal. Offering federated servers would also allow users to secure their own servers.
        s_ting765 4y ago
        > secure enclave will get better with time Intel already dropped SGX from their new line up of CPUs (11th gen +). https://news.ycombinator.com/item?id=29932630 https://news.ycombinator.com/item?id=29932630
lukeschlather 4y ago
Most of Signal's "competitors" don't just keep a plaintext database of every pair of users that have communicated, they keep a plaintext database of every conversation. (GChat is at least good about making expiring conversations visible and easy.) There's not necessarily "alternatives" most of the competitors offer a much richer feature set and Signal has stripped away those features down to what they see as the bare minimum.
- tptacek 4y ago
  It would be more accurate to say that Signal has stripped its features down to those it can implement safely without keeping serverside databases of communications metadata. It's surprisingly hard to do that, and so Signal has noticeably fewer features than things like Matrix, which suffered calamitous security vulnerabilities as a result.

tptacek 4y ago

Your Signal contact list is your device's contact list, keyed by phone numbers.

O__________O 4y ago
For clarity, this assumes you allow Signal access to the device’s contact list, which is not required.
- palata 4y ago
  For clarity, you allow the open source client app (which you can audit and compile yourself) to securely share your contact list with a secure enclave (which is open source so you can audit it as well).
  - O__________O 4y ago
    The client-side contact list is one of two lists: (a) device’s contact list if Signal is given access — or (b) list of numbers that have manually been add to the App and Signal is not given access to device’s contact list because user declined providing it access. Also, might be wrong, but appears Signal’s secure enclave, which is based on Intel’s SGX technology, is known to be vulnerable to side-channel attacks and Intel’s SGX code & hardware is not open source: https://medium.com/@maniacbolts/signal-increases-their-reliance-on-sgx-f46378f336d3 https://medium.com/@maniacbolts/signal-increases-their-relia...
    - palata 4y ago
      Yep, you have to trust the secure enclave for this to work!
      - O__________O 4y ago
        No, you have to trust anyone with access to the server; secure enclave provides no security given it appears it is vulnerable to side channel attacks; see comment you just replied to for related link. Basically all it does is given Signal plausible deniability for public search warrants: https://signal.org/bigbrother/ https://signal.org/bigbrother/ It would do nothing to stop national security letters. Basically, you should assume the functionality provided by the secure enclave is only in name; given the NSA ATT national security letters enabled both physical access and system modifications, see no reason to believe others would not be required to do so as well: https://en.m.wikipedia.org/wiki/Room_641A https://en.m.wikipedia.org/wiki/Room_641A Again, average person does not have a threat model that makes this relevant, but to say Signal does not have access to the SGX data is purely based on trust, not mathematical proofs.
        palata 4y ago
        At that point, your phone is vulnerable. As is your computer, and your connected fridge. If your threat model does not allow it, use manual e2ee with pigeons. Otherwise, well secure enclave will get better with time, which will make Signal better too.
        O__________O 4y ago
        Signal should make threats clear to users, just as they should have notified all users that multiple 3rd parties downloaded all the phone numbers in Signal. Offering federated servers would also allow users to secure their own servers.
        s_ting765 4y ago
        > secure enclave will get better with time Intel already dropped SGX from their new line up of CPUs (11th gen +). https://news.ycombinator.com/item?id=29932630 https://news.ycombinator.com/item?id=29932630

lukeschlather 4y ago

Most of Signal's "competitors" don't just keep a plaintext database of every pair of users that have communicated, they keep a plaintext database of every conversation. (GChat is at least good about making expiring conversations visible and easy.) There's not necessarily "alternatives" most of the competitors offer a much richer feature set and Signal has stripped away those features down to what they see as the bare minimum.

tptacek 4y ago
It would be more accurate to say that Signal has stripped its features down to those it can implement safely without keeping serverside databases of communications metadata. It's surprisingly hard to do that, and so Signal has noticeably fewer features than things like Matrix, which suffered calamitous security vulnerabilities as a result.