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How is that possible? Bitcoin's whole premise is a globally verifiable balance of each address after each block (aka public ledger). I could see this being very

How is that possible? Bitcoin's whole premise is a globally verifiable balance of each address after each block (aka public ledger). I could see this being very helpful for new crypto currencies, but Bitcoin is pretty set in stone on this matter, no?

askmike 8y ago
I don't think this will ever be hardforked into bitcoin, but there are other ways of getting this in, such as via sidechains (see liquid[1] for example). [1] https://blockstream.com/liquid/ https://blockstream.com/liquid/
zodiac 8y ago
Well, the verification guarantees you want out of a public ledger for currency are weaker than that (no money is created out of thin air, the person you're receiving money from actually has enough money to send to you, etc). I'm not sure anyone is philosophically attached to "all balances are visible".
- infogulch 8y ago
  Ok yes, in a single transaction you can prove to everyone else that the net exchange is zero, but how do you prove that you have enough money to send to them? That's global state that depends on all past transactions, even if they're hidden. Include more ZKPs for every transaction ever associated with that address? You have to prove that 1. you received enough to cover it and 2. you haven't spent it already. Just slapping some ZKP on top of bitcoin is not enough to make it magically private. It needs deeper integration to the model than that.
  - jlrubin 8y ago
    You take the commitments from the outputs and use them in the next proof. It is possible to soft fork confidentiality into Bitcoin, see https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-January/012194.html https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016... for example
- antpls 8y ago
  > I'm not sure anyone is philosophically attached to "all balances are visible". I don't know either about others, but to me it looks like hiding balances is a regression. Why would you hide your balance, unless you want to lie about it? I can't think of a reason hiding balances would be better, but I don't have a degree about economy so I'm open to explanation. Same argument than personal privacy I guess, but here we are talking about currency, not personal political opinions or personal identifyable information.
jlrubin 8y ago
These are publicly verifiable, they are just not plaintext values anymore. This isn't so weird -- think about what a signature is, it's a proof that I know a private key without plaintext revealing the key.

askmike 8y ago

I don't think this will ever be hardforked into bitcoin, but there are other ways of getting this in, such as via sidechains (see liquid[1] for example). [1] https://blockstream.com/liquid/ https://blockstream.com/liquid/

zodiac 8y ago

Well, the verification guarantees you want out of a public ledger for currency are weaker than that (no money is created out of thin air, the person you're receiving money from actually has enough money to send to you, etc). I'm not sure anyone is philosophically attached to "all balances are visible".

infogulch 8y ago
Ok yes, in a single transaction you can prove to everyone else that the net exchange is zero, but how do you prove that you have enough money to send to them? That's global state that depends on all past transactions, even if they're hidden. Include more ZKPs for every transaction ever associated with that address? You have to prove that 1. you received enough to cover it and 2. you haven't spent it already. Just slapping some ZKP on top of bitcoin is not enough to make it magically private. It needs deeper integration to the model than that.
- jlrubin 8y ago
  You take the commitments from the outputs and use them in the next proof. It is possible to soft fork confidentiality into Bitcoin, see https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016-January/012194.html https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2016... for example
antpls 8y ago
> I'm not sure anyone is philosophically attached to "all balances are visible". I don't know either about others, but to me it looks like hiding balances is a regression. Why would you hide your balance, unless you want to lie about it? I can't think of a reason hiding balances would be better, but I don't have a degree about economy so I'm open to explanation. Same argument than personal privacy I guess, but here we are talking about currency, not personal political opinions or personal identifyable information.

jlrubin 8y ago

These are publicly verifiable, they are just not plaintext values anymore. This isn't so weird -- think about what a signature is, it's a proof that I know a private key without plaintext revealing the key.