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Signal was once subpoenaed by the FBI to give up all stored data/metadata relating to a certain account. They responded with the account creation timestamp and
by majewsky 8y ago
Signal was once subpoenaed by the FBI to give up all stored data/metadata relating to a certain account. They responded with the account creation timestamp and the last-connected timestamp, suggesting that they do not store information about group ownerships or contacts.
Source: https://www.aclu.org/blog/national-security/secrecy/new-documents-reveal-government-effort-impose-secrecy-encryption https://www.aclu.org/blog/national-security/secrecy/new-docu...
- tinus_hn 8y agoOnce they become big they will be forced to keep that data. It is really difficult to force them to change the client or the protocol but not to force them to keep data they have access to on the server.
- baby 8y agoThis is because Signal works differently for group chat. In WhatsApp, the server delivers your encrypted message to each member of the group. It's an optimization called "server-side fan-out". Check the whitepaper for more deatils: https://www.whatsapp.com/security/WhatsApp-Security-Whitepaper.pdf https://www.whatsapp.com/security/WhatsApp-Security-Whitepap... Interestingly this is also what the Signal libraries implement. So applications making use of them will generally make use of this optimization. For some reason, the Signal application itself was not making use of this optimization. My guess is that it had not updated its code yet when I looked. This might have changed since then. BUT, and that's a big but, as a passive observer (and if Signal kept logs of things) you can still figure out group chat membership by looking at who sent the same kind of message (same length) to who, and at what time. Basic relationship graph stuff.