Nice work @barborrico !
Just a little correction, if all witnesses stop to post units, user units will be validated by other users posting units. Users help each other.
In plus of validating users units as normal users, witnesses help users as milestones/lighthouses to find the path until the genesis unit. Once the witnesses' majority crossed, the last witness crossed acts like a shortcut until the genesis unit.
If witnesses stop posting, users will take a lot of time to reach the genesis unit... or the last witnesses' majority and so a shortcut to the genesis unit. The genesis unit could be really far away.
if witnesses stop posting, the stability point would not progress meaning transactions would not confirm. The DAG would still grow if new units are added but in case of double spends there would be no consensus which one to pick.
I thought without witnesses byteball is open to sybil attacks. Is it not, really?
Anyway, I try to write with general understanding in mind rather than techical accuracy. For that, you are better than me for sure.
You're better than you think @barborrico. I'm a bit drafty and @byteball.market's clarification is better than my own answer 😉
Indeed, stability point would not progress.
The user, if honest, could - theoritically - discover a partial order at the cost of a big travel back in time until last witnesses posts. This effort could keep the unit unsable a lot of time independently of new posted units by other users.
Worst, there will have no definition of rendez-vous point allowing user to synchronize/merge his path until the genesis unit with a stable chain. Result will be total chaos and systematic redefinitions of the best path will occur. By itself, the path is not deterministic and bifurcations are always possible without the witnesses.
In plus, if there are suspicious units posted that require the total order to be deemed valid, it will be the drama.
I need a coffee 😪
Thank you both !