There are firms that sell phone scanning utilities that pull signal message off (unlocked?) ios and android (and presumably desktops).
Even if signal used an enclave key to encrypt the local chat database, sgx doesn’t protect the enclave from the keyboard, mouse or display drivers, so someone could simply write a screen scraper that displayed and captured each message of each thread.
Even if signal used an enclave key to encrypt the local chat database, sgx doesn’t protect the enclave from the keyboard, mouse or display drivers, so someone could simply write a screen scraper that displayed and captured each message of each thread.