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The article calls out that the Signal server could be compromised. I always thought one design philosophy of Signal was to ensure the server doesn’t matter from

by tass 6y ago

The article calls out that the Signal server could be compromised. I always thought one design philosophy of Signal was to ensure the server doesn’t matter from the perspective of privacy. Would having multiple servers help here, anyway? Once your data leaves your own server, you would then be in untrusted territory assuming the server needed to be trusted.

walrus01 6y ago
It's my understanding that the main concern about a compromised Signal server is that metadata of which phone numbers are registered as user IDs could be compromised. Basically the same threat model the Signal people themselves address when talking about court orders and subpoeanas received by their corporation for "customer" data.
- solstice 6y ago
  That's not true afaik. Signal days that they don't store phone numbers beyond the initial setup/verification. See here: > Does Signal send my number to my contacts? Signal does not send your phone number to anyone unless you send them a message or make a call to them. The Signal service does not have any knowledge of your contacts. Data is all owned by your phone. Registration notifications are never transmitted by anyone in any direction at all; these notifications are created by your phone. > How does Signal know my contact is using Signal? Signal periodically sends truncated cryptographically hashed phone numbers for contact discovery. Names are never transmitted, and the information is not stored on the servers. The server responds with the contacts that are Signal users and then immediately discards this information. Your phone now knows which of your contacts is a Signal user and notifies you if your contact just started using Signal. https://support.signal.org/hc/en-us/articles/360007061452-Does-Signal-send-my-number-to-my-contacts- https://support.signal.org/hc/en-us/articles/360007061452-Do... (Btw, I think that first sentence is a bit confusing and should be classified/reworded.)
  - hiq 6y ago
    Some of these features are using SGX, which is why people dismiss them. Using SGX is still better than nothing, and there's no better alternative given the simplicity goals of Signal (e.g. selecting manually which of your contacts has Signal is not an option).
  - xorcist 6y ago
    > truncated cryptographically hashed phone numbers These would be equivalent to phone numbers, for all intents and purposes. The number space is trivially small. This kind of obscurity makes it unnecessarily hard to understand what the argument really is.

by tass 6y ago

walrus01 6y ago

It's my understanding that the main concern about a compromised Signal server is that metadata of which phone numbers are registered as user IDs could be compromised. Basically the same threat model the Signal people themselves address when talking about court orders and subpoeanas received by their corporation for "customer" data.

solstice 6y ago
That's not true afaik. Signal days that they don't store phone numbers beyond the initial setup/verification. See here: > Does Signal send my number to my contacts? Signal does not send your phone number to anyone unless you send them a message or make a call to them. The Signal service does not have any knowledge of your contacts. Data is all owned by your phone. Registration notifications are never transmitted by anyone in any direction at all; these notifications are created by your phone. > How does Signal know my contact is using Signal? Signal periodically sends truncated cryptographically hashed phone numbers for contact discovery. Names are never transmitted, and the information is not stored on the servers. The server responds with the contacts that are Signal users and then immediately discards this information. Your phone now knows which of your contacts is a Signal user and notifies you if your contact just started using Signal. https://support.signal.org/hc/en-us/articles/360007061452-Does-Signal-send-my-number-to-my-contacts- https://support.signal.org/hc/en-us/articles/360007061452-Do... (Btw, I think that first sentence is a bit confusing and should be classified/reworded.)
- hiq 6y ago
  Some of these features are using SGX, which is why people dismiss them. Using SGX is still better than nothing, and there's no better alternative given the simplicity goals of Signal (e.g. selecting manually which of your contacts has Signal is not an option).
- xorcist 6y ago
  > truncated cryptographically hashed phone numbers These would be equivalent to phone numbers, for all intents and purposes. The number space is trivially small. This kind of obscurity makes it unnecessarily hard to understand what the argument really is.