When you want a friend to add you on Keychat, you have two options: tell them your QR code or your Npub. We recommend using the QR code because once someone knows your QR code, they can send you messages encrypted with Signal directly, and the QR code is only valid for 24 hours. If you use your Npub, after someone knows your Npub, the first message can only be encrypted with NIP4 or NIP17. Only after they reply can messages be encrypted with Signal. 

 Cool, thank you, that makes sense. 

Three more questions if you want to answer
 - can I use my own relay? 
 - how would you compare keychat to SimpleX and Signal? When would you use which?
 - groups support?

I'm going to set it up, play with it and update:

https://juraj.bednar.io/en/blog-en/2022/05/03/encrypted-messengers-comparison/ 

 1、yes, of course.  see below note.

nostr:note15sza0s4yrxzx35cn3cs5xarxd48h7tgc5eyy4x0ml98jqfrk92gswyvhc8

2、 see below note 

nostr:note186wfn3zdrds9g3k2rgqxtzxxr3azfzr3vz6aa68c52kns7wqpduspmk2hh

3、yes, two kinds of group. 

nostr:note1927pnd00l22umju9xldyjc3xsrhn28tk0rxczn50pygwaft5h8kqcex9y9