Moxie did a great post on private contact discovery and why, as far as we know, it currently isn't practical: https://whispersystems.org/blog/contact-discovery

Moxie did a great post on private contact discovery and why, as far as we know, it currently isn't practical: https://whispersystems.org/blog/contact-discovery/ https://whispersystems.org/blog/contact-discovery/ The bottom line is, you can't make a find_friends function that's remotely privacy conscious or secure against the approach taken here against Snapchat. Snapchat are effectively offering a public phone directory at this point, and they won't be able to fix it.