tx-pointer gets overridden by any key(share) message

[fredo]

@konradkonrad please post your observations

[konradkonrad]

I was mistaken:

It looked as if a rogue keyper could arbitrarily change other keyper's tx-pointers:

https://github.com/shutter-network/rolling-shutter/blob/f21a5db5b27894dddc384d975418397c8858832e/rolling-shutter/keyperimpl/gnosis/handlers.go#L295-L315

as long as the message validates for the receivers.

However, the prerequisites for validation are:

• valid message layout
• valid signatures of at least threshold validators

So this is "threshold safe", as far as I understand!

The tx-pointer value that will be updated by a DecryptionKeys message, is being voted upon during KeyShares gossiping.