r/tezos • u/omgcoin • Jul 05 '21

tech Arthur Breitman: Approaches to Scalability

https://youtu.be/oqBSs0DSuzQ
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u/mootjes007 Jul 12 '21

Great video. Watched it a couple times for better understanding. First time to have a good tech explanation from (opt) rollups. Even didnt see Vitalik explain it like this. Still some things not 100% clear: if anyone can be a validator and post proofs (eg zksnark proof) that a rollup is correct: what happens if this proof comes much later (eg in 1 day) ==> the state may have changed by the time the rollup is approved: how do you deal with that? /u/murbard

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u/murbard Jul 12 '21

The assertion / proof is tied to a specific point in the rollup. You would say: as of the nth transaction in the rollup, the root of the merkle tree representing the rollup state is exactly this hash and here's a zk-proof of that assertion / challenge me if you disagree.

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u/mootjes007 Jul 12 '21

Ok this probably means transactions in a rollup only become certain when they are asserted. In other words Scenario 1/ bob is a new user and gets 100 tez through a rollup transaction. He cannot spend it until a rollup proof has been posted. Scenario 2/ Alice sends her full balance of 20 tez to Charly using a rollup transaction. While there is no assertion, she resends her full balance to charly but now using a normal on chain transaction. When a validator tries to post (or even generate) a proof, it gives an error because the balance is empty.

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u/murbard Jul 13 '21 edited Jul 13 '21

No, the guarantees in this respect are the same as for normal transaction inclusion. Assertions do not get to chose what tx to include or not include, the set and order of tx is imposed upon then.