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How blocks are chained in a blockchain

johndcook.com

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Re: How blocks are chained in a blockchain

#31

Post by OneDeuxTriSeiGo »

dollylambda wrote: post #19
coolThingsFirst wrote: post #12

Earlier quoted context omitted.

has there been any useful application of this outside of bitcoin as currency? Seems like a solid technical idea with lots of woo-woo on top of it.

You could argue the useful application has been that of a time-stamping service, which is what you need to order a transaction history.

Yeah at it's core a blockchain based cryptocurrency is a consensus system and decentralised resource market where the resource in question is space in the blocks within some time bound and verifiable proof of the time and state they were accepted in.

That core feature of "providing a total ordering for state changes and events with formal trust bounds" turns out to have a lot of potential uses.

Now of course truly providing correct timestamps or really any clock mechanism in a trustless way turns out to be massively difficult. And not just in a blockchain but really in any decentralised/distributed system. It's a famously unsolved problem.

There's some research[1] on how to go about providing a "global time"/"global clock" for cryptocurrencies without external trust assumptions but it's extraordinarily academic and most if not all systems just assume trusted time within some bound and hope for the best.

1. Permissionless Clock Synchronization with Public Setup - https://eprint.iacr.org/2022/1220

Re: How blocks are chained in a blockchain

#32

Post by dollylambda »

OneDeuxTriSeiGo wrote: post #31
dollylambda wrote: post #19

Earlier quoted context omitted.

You could argue the useful application has been that of a time-stamping service, which is what you need to order a transaction history.

Yeah at it's core a blockchain based cryptocurrency is a consensus system and decentralised resource market where the resource in question is space in the blocks within some time bound and verifiable proof of the time and state they were accepted in. That core feature of "providing a total ordering for state changes and events with formal trust bounds" turns out to have a lot of potential uses. Now of course truly pr…

In a sense, a POW blockchain such as bitcoin can convey global time/global clock if all participants understand the average block propagation is 10 "minutes"? Sometimes longer, sometimes shorter but converges to 10 minutes in aggregate.

Over great distances this breaks down given limits on the speeds of transmition (speed of light), however, if transmission was instantaneous (quantum entanglement?), that would solve the dilemma of what does "now" mean light-years away given our relativistic idea of time between here and there.

Re: How blocks are chained in a blockchain

#33

Post by OneDeuxTriSeiGo »

dollylambda wrote: post #32
OneDeuxTriSeiGo wrote: post #31

Earlier quoted context omitted.

Yeah at it's core a blockchain based cryptocurrency is a consensus system and decentralised resource market where the resource in question is space in the blocks within some time bound and verifiable proof of the time and state they were accepted in. That core feature of "providing a total ordering for state changes and events with formal trust bounds" turns out to have a lot of potential uses. Now of course truly pr…

In a sense, a POW blockchain such as bitcoin can convey global time/global clock if all participants understand the average block propagation is 10 "minutes"? Sometimes longer, sometimes shorter but converges to 10 minutes in aggregate. Over great distances this breaks down given limits on the speeds of transmition (speed of light), however, if transmission was instantaneous (quantum entanglement?), that would solve…

Oh yeah. Sorry I misspoke a bit. I should have said that global time/clocks are an unsolved problem in non-proof-of-work systems.

Proof of work does a decent job approximating a monotonic clock but that only works when you are expending obscene amounts of energy on a global scale. And like you said it breaks down over longer distances (however luckily we don't have to deal with that too much now).

But in any non-PoW system, a "trustless" global clock is extremely non-trivial.

Re: How blocks are chained in a blockchain

#34

Post by dollylambda »

OneDeuxTriSeiGo wrote: post #33
dollylambda wrote: post #32

Earlier quoted context omitted.

In a sense, a POW blockchain such as bitcoin can convey global time/global clock if all participants understand the average block propagation is 10 "minutes"? Sometimes longer, sometimes shorter but converges to 10 minutes in aggregate. Over great distances this breaks down given limits on the speeds of transmition (speed of light), however, if transmission was instantaneous (quantum entanglement?), that would solve…

Oh yeah. Sorry I misspoke a bit. I should have said that global time/clocks are an unsolved problem in non-proof-of-work systems. Proof of work does a decent job approximating a monotonic clock but that only works when you are expending obscene amounts of energy on a global scale. And like you said it breaks down over longer distances (however luckily we don't have to deal with that too much now). But in any non-PoW…

Thats because POW solves the Byzantine Generals problem as I understand it. Before POW, that problem was intractable (extremeley non-trivial). Its always lammented that so much energy is needed to solve the problem, although that seems to be the nature of the problem. Maybe time and energy are inexorably linked.

Re: How blocks are chained in a blockchain

#35

Post by OneDeuxTriSeiGo »

dollylambda wrote: post #34
OneDeuxTriSeiGo wrote: post #33

Earlier quoted context omitted.

Oh yeah. Sorry I misspoke a bit. I should have said that global time/clocks are an unsolved problem in non-proof-of-work systems. Proof of work does a decent job approximating a monotonic clock but that only works when you are expending obscene amounts of energy on a global scale. And like you said it breaks down over longer distances (however luckily we don't have to deal with that too much now). But in any non-PoW…

Thats because POW solves the Byzantine Generals problem as I understand it. Before POW, that problem was intractable (extremeley non-trivial). Its always lammented that so much energy is needed to solve the problem, although that seems to be the nature of the problem. Maybe time and energy are inexorably linked.

Well it's a bit more complex than that but the two are certainly linked given that POW is framed in the context of time complexity of the problem and the adjusting difficulty is just an equation to approximate a clock from the rate of solutions produced for a problem of a given time complexity with an approximate X amount of available resources.
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