# Technology preview: Private contact discovery for Signal

DevFeed: [Technology preview: Private contact discovery for Signal](<https://devfeed.tech/articles/technology-preview-private-contact-discovery-for-signal-1809.md>)

Original publisher: [Read original article](<https://signal.org/blog/private-contact-discovery/>)

Published: 2017-09-26T00:00:00Z

Content type: article

Language: en

Sources: [Signal Blog](<https://devfeed.tech/sources/signal-blog.md>)

Topics: [zero-knowledge](<https://devfeed.tech/topics/zero-knowledge.md>), [Graphs](<https://devfeed.tech/topics/graphs.md>), [Software](<https://devfeed.tech/topics/software.md>), [App](<https://devfeed.tech/topics/app.md>)

Tags: [app](<https://devfeed.tech/tags/app.md>), [communication](<https://devfeed.tech/tags/communication.md>), [privacy](<https://devfeed.tech/tags/privacy.md>), [software](<https://devfeed.tech/tags/software.md>), [technology](<https://devfeed.tech/tags/technology.md>), [zero-knowledge](<https://devfeed.tech/tags/zero-knowledge.md>)

## AI overview

Signal introduces a private contact discovery service that lets clients determine which address-book contacts use Signal without revealing the address book to Signal. The article explains the privacy challenges of building a social graph while avoiding a durable server-side record of users' contacts.

## Source excerpt

At Signal, we've been thinking about the difficulty of private contact discovery for a long time. We've been working on strategies to improve our current design, and today we've published a new private contact discovery service. 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. Read more...