Engine/Sync Protocol

First sketch / Rough idea

23:15 <fdik> 1) Device creates device key
23:15 <fdik> 2) Device sends discovery message to all own addresses
23:16 <fdik> 3) Answer comes from one or more devices: “This is a device group.  
             Here is a public key to receive the group key”
23:16 <fdik> 4) New device answers “got it, let's handshake”
23:17 <fdik> 5) All devices do a handshake with the new device's key and the group key
23:18 <fdik> 6) If accepted on at least one device of group and new device,  
             sec key of device group is sent to new device encrypted with its device key. 
             signed with itself.
23:18 <fdik> 7) New device uses group key then

Current implementation in p≡p engine

See: [https://pep.foundation/dev/repos/pEpEngine/file/tip/sync/].