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Comment by ulrikrasmussen | Hacker News Reader

But that assumes that there is a trusted archival party that can verify account balances with authority. It may be technically possible to devise such a system, but as far as I understand, current decentralized blockchains require that you replay all previous transactions in order to learn the current state of the system.

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I'm new to blockchains so I'm sorry if this is stupid, maybe somebody can explain to me.

Why do everybody needs to keep everything? The chain will be much smaller with just the id and the hash of the block. The payloads could be kept only by the interested parties and could be validated when needed with the chain.

Look at R3 Corda, transactions only shared and stored between parties involved, not the rest of the network.

> Why do everybody needs to keep everything?

Because every node in the network must be able to verify all transactions all the way from the genesis block. In order to ensure that this is possible, everyone who keeps the history must keep the full history.

With the MimbleWimble design [1] [2], inputs may be cancelled against the outputs they spend, with no loss of security. Essentially, the entire blockchain history may be collapsed to a single mega transaction, with all coinbases as inputs and the UTXO set as outputs.

[1] http://mimblewimble.cash/20160719-OriginalWhitePaper.txt

[2] https://www.youtube.com/watch?v=ovCBT1gyk9c

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