The DO NOT slurp your contacts. They invented a way to do contact discovery in a secure way: https://signal.org/blog/private-contact-discovery/ https://signal.

The DO NOT slurp your contacts. They invented a way to do contact discovery in a secure way: https://signal.org/blog/private-contact-discovery/ https://signal.org/blog/private-contact-discovery/. From the article: "Using this service, Signal clients will be able to efficiently and scalably determine whether the contacts in their address book are Signal users without revealing the contacts in their address book to the Signal service." This is why Signal gets so much benefit of the doubt from the cryptography/security/privacy community. Their default approach to these problems is conservative in favor of the user until they can invent the technology needed to support a feature with security/privacy.