Technology Preview: Signal Private Group System
Again, in the theme of &quot;features every group messaging system had already, but Signal didn&#x27;t, because they hadn&#x27;t figured out a way to implement it without turning Signal&#x27;s central servers into a database of who&#x27;s talking to who about what&quot;. Signal didn&#x27;t even have <i>user profiles</i> until recently, for the same reason. Here, they&#x27;ve slightly expanded the state of the art in MAC-based anonymous credentials to accomplish their goal.<p>One interesting aspect of this is that Signal gets to do this, because they have immense goodwill with the cryptographic research and engineering communities; though it&#x27;s no guarantee of soundness, they have the advantage of having the feature designed, implemented, and ultimately reviewed by cryptography engineers that aren&#x27;t generally&#x2F;economically available to other messaging projects.<p>This is either a reason you <i>love</i> Signal (raises hand) or <i>can&#x27;t stand</i> Signal. My take is, if you&#x27;re in the latter group, that&#x27;s fine; I use Slack, too.