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Signal's use of phone numbers is an absolutely terrible practice and is one of a number of reasons for which I condemn it. In particular, Signal's use of phone

Signal's use of phone numbers is an absolutely terrible practice and is one of a number of reasons for which I condemn it. In particular, Signal's use of phone numbers cannot be independent of SMS routing as you propose, because Signal must have some way of verifying that someone actually controls a given number, i.e., by sending messages to it. So however Signal anchors cryptographic identities to phone numbers, it has the telephone network's routing infrastructure as its ultimate anchor and thus as its Achilles heel.

BugsJustFindMe 5y ago
> Signal's use of phone numbers cannot be independent of SMS routing as you propose I didn't say anything about how Signal decides on routes. I said that Signal uses phone numbers as identifiers. If Signal wanted to make you verify "ownership" of your identifier some other way, that would not change anything about the nature of the system other than its ease of initial setup. Both sending a message to a phone number assigned from a phone number registrar and sending a message to an internet domain name assigned from a domain registrar are sending messages addressed with identifiers assigned by registrars. Even if the implementations themselves differ, those differences are not condemnations of the principle of sending messages to identifiers. And it looks bad when you start using arguments like "phone number registrars are more gullible than domain registrars" as if that's not entirely circumstantial, speculative, and un-intrinsic to the technology or the business.
- hlandau 5y ago
  So what is to stop me from signing up for a Signal account using your phone number? It's patently obvious that to use phone numbers as identifiers you have to prove control over them at some point. That involves the telephone network. Thus any service which uses phone numbers to identify people necessarily inherits the security issues of that network. Edit: Yes, and I'm saying that the latter can actually be secure.
  - BugsJustFindMe 5y ago
    > That involves the telephone network. No, you misunderstand me. The reason I didn't say anything about the transport mechanism is because it doesn't make a fundamental difference. People hijack domains and internet packet routes through both technological and social engineering attacks literally all the time. None of the complaints in your post have anything to do with any essential or necessary characteristics of phone numbers or phone networks or phone service operators. Email messages are routed to your domain by a gentleperson's handshake agreement between networks outside of your control plus a little bit of government regulation in exactly the same way that phone messages are routed to your phone by gentleperson's handshake agreement between networks outside of your control plus a little bit of government regulation. All possible arguments about routing trust being violated apply equally to both networks. All possible ideas about layering security on top of the network, like e.g. TLS handshakes, apply equally to both networks. > It's patently obvious that to use phone numbers as identifiers you have to prove control over them at some point. Signal doesn't ask for your phone number to prove the network path for your messages. What they're trying to assess is whether some entry in someone else's contacts list can be associated with your identity. If they wanted to, they could ask you to show up in person with a valid phone service contract and let them set up your client account directly. People just wouldn't bother to use Signal then. > So what is to stop me from signing up for a Signal account using your phone number? The same exact things that stop me from signing up for things using your email address. I could get someone to route requests for your domain to my servers if I had sufficient criminal intent.

BugsJustFindMe 5y ago

> Signal's use of phone numbers cannot be independent of SMS routing as you propose I didn't say anything about how Signal decides on routes. I said that Signal uses phone numbers as identifiers. If Signal wanted to make you verify "ownership" of your identifier some other way, that would not change anything about the nature of the system other than its ease of initial setup. Both sending a message to a phone number assigned from a phone number registrar and sending a message to an internet domain name assigned from a domain registrar are sending messages addressed with identifiers assigned by registrars. Even if the implementations themselves differ, those differences are not condemnations of the principle of sending messages to identifiers. And it looks bad when you start using arguments like "phone number registrars are more gullible than domain registrars" as if that's not entirely circumstantial, speculative, and un-intrinsic to the technology or the business.

hlandau 5y ago
So what is to stop me from signing up for a Signal account using your phone number? It's patently obvious that to use phone numbers as identifiers you have to prove control over them at some point. That involves the telephone network. Thus any service which uses phone numbers to identify people necessarily inherits the security issues of that network. Edit: Yes, and I'm saying that the latter can actually be secure.
- BugsJustFindMe 5y ago
  > That involves the telephone network. No, you misunderstand me. The reason I didn't say anything about the transport mechanism is because it doesn't make a fundamental difference. People hijack domains and internet packet routes through both technological and social engineering attacks literally all the time. None of the complaints in your post have anything to do with any essential or necessary characteristics of phone numbers or phone networks or phone service operators. Email messages are routed to your domain by a gentleperson's handshake agreement between networks outside of your control plus a little bit of government regulation in exactly the same way that phone messages are routed to your phone by gentleperson's handshake agreement between networks outside of your control plus a little bit of government regulation. All possible arguments about routing trust being violated apply equally to both networks. All possible ideas about layering security on top of the network, like e.g. TLS handshakes, apply equally to both networks. > It's patently obvious that to use phone numbers as identifiers you have to prove control over them at some point. Signal doesn't ask for your phone number to prove the network path for your messages. What they're trying to assess is whether some entry in someone else's contacts list can be associated with your identity. If they wanted to, they could ask you to show up in person with a valid phone service contract and let them set up your client account directly. People just wouldn't bother to use Signal then. > So what is to stop me from signing up for a Signal account using your phone number? The same exact things that stop me from signing up for things using your email address. I could get someone to route requests for your domain to my servers if I had sufficient criminal intent.