[dayon]

Just to clarify, if you use Signal, there is no meta-data. Who you called, who called you, the call times, and so on are hidden. It's like with Tor and how your browsing history isn't saved. All the WIFI network operator can know is that you accessed Signal to make a call / text.

[kobayashi]

Uh, I'm not sure about that. TOR uses many layers of obfuscation in its attempt to hide where your traffic is going. I think Signal does no such thing, and this metadata is insecure. Also, I think your mention of browsing history is a non sequitur.