  Secure messaging applications often offer privacy to users by protecting
their messages from would be observers through end-to-end encryption
techniques. However, the metadata of who communicates with whom cannot be
concealed by encryption alone. Signal's Sealed Sender mechanism attempts to
enhance its protection of this data by obfuscating the sender of any message
sent with the protocol. However, it was shown by Martiny et al. that due to the
message delivery protocols in Signal, the record of who receives messages can
be enough to recover this metadata. In this work we extend the attack presented
from deanonymizing communicating pairs to deanonymizing entire group
conversations.
