Signal service doesn't store message routing meta data nor what groups you are in. In response to a subpoena for specific user's data: "the only information w

Signal service doesn't store message routing meta data nor what groups you are in. In response to a subpoena for specific user's data: "the only information we can produce in response to a request like this is the date and time a user registered with Signal and the last date of a user's connectivity to the Signal service." https://whispersystems.org/bigbrother/ https://whispersystems.org/bigbrother/