@Nikolai "Or instead of 3. is there some gathering to stop each member of an N sized cabal having to store N-1 shards, emanating for all the other cabal member's keys?"

this is something which @Kieran and I have spoken about but we haven't sat down and figured out a formal proof for what all of this means - which I have taken on I think a bit with pb to review.

But, yes - what you are getting at is correct, but we have not expanded on implications and effects...

So in the case of sharding a multi-sig wallet are you/we/mmt saying:

1. Agree the cabal members, the min required members for the wallet, the min required shards to re-create a key
2. Each person share's their xpub (in a secure way) with the cabal
3. At the same time as 2. they shard their private key with the cabal

Very loosely, yes this is my understanding of the of the MVP.

It's useful having your detail and programming lense in on it as these are the details that we need to figure out.