Blockchain Is Puny | Hacker News Reader

Blockchain Is Puny

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29 pointselsewhen55 comments

Kind of an aside, but as the post talks about all the work needed to be done to verify additions to the blockchain, that also implies people could be adding invalid content to the blockchain. Usually invalid stuff is easier to confirm than valid, but still, how easy is it to use invalid additions to spam the chain? Do valid transactions get validated on top of invalid transactions and require revalidation? Or is the initiator of the transaction responsible for recreating on a valid basis?

I'm sure this is all basic blockchain stuff but it hadn't occurred to me before...

The "proof" part of proof of work used by Bitcoin is a small piece of information that proves that a lot of work has been done. An invalid proof can be easily checked by other nodes and ignored. In the case of Bitcoin the proof is a set of alphanumeric characters as input to the hashing algorithm (SHA256 I think) that produces a hash with certain properties (some number of leading zeros depending on the current difficulty). Other nodes can verify the proof by taking the input supplied by the miner, combining it with a predetermined nonce and computing the hash and checking that it has the properties required. Computing a single SHA256 is easy compared to figuring out which input to the hash produces a particular output.

The next mined block will be appended to the longest valid blockchain the node can see. It's in their interest to append to the one that others will believe, because they get paid the reward only on that chain and thus it only exists in their wallet if others accept it by appending further blocks to it. So generating invalid blocks just doesn't work - they get immediately rejected by other nodes and there is thus no reward.

One genuine problem is mining a valid block but adding no transactions to it, to grind transaction throughput to a halt. I think Bitcoin might have some mitigations for this but I don't actually know. If a sufficiently well funded organisation or nation tried to take down Bitcoin this might be the way to do it.

Empty blocks generate less revenue (no transaction fees, only the minig reward) but are slightly easier to create due to small mathematical flaws that let you skip some work if the block you create is empty. So for certain pools it's profitable in aggregate to mine empty blocks.

Empty block mining has gone down significantly over time.

2018 https://www.theblockcrypto.com/linked/1964/close-to-19-of-mi...

2020 https://www.theblockcrypto.com/post/67928/bitcoin-miners-are...

and stratum v2 gets rid of it entirely...

https://braiins.com/blog/why-pools-mine-empty-blocks-and-how...

"mining pools will be able to dig deeper into the mempool (for transactions that are unlikely to be included in the current block) and construct full block templates before the current block is found. Then they can send those block templates to miners ahead of time when the latency doesn’t matter, so that only the prevhash message needs to be sent to actually start the new mining round."

If you try to include any invalid transaction in the proof, you will not (w.h.p.) be able to create the proof condition. So that update would be rejected. It is up to the proof generator to verify their transactions before including them in a proof. A proof verifier can accept or reject a proof trivially.

I’m still trying to understand why it is so evil that a centralised authority controls a transaction ledger. Why, exactly, is this a bad thing?

"so evil that a centralised authority controls", repeat your own sentence a few times.

I by and large think the Reserve Bank if Australia is benign.

Among the many reasons: because they can censor the ledger to make it impossible for you to pay for the vegetables you prefer to smoke.

Or shut off your PayPal, or block your business from taking credit cards, because they personally find your business unsavory, and soon you won't be able to take cash because there's a worldwide push to get rid of it, and many other reasons.

lol Paypal:

https://www.paypal.com/us/webapps/mpp/ua/acceptableuse-full

You may not use the PayPal service for activities that:

* violate any law, statute, ordinance or regulation.

* relate to transactions involving (a) narcotics, steroids, certain controlled substances or other products that present a risk to consumer safety, (b) drug paraphernalia, (c) cigarettes, (d) items that encourage, promote, facilitate or instruct others to engage in illegal activity, (e) stolen goods including digital and virtual goods, (f) the promotion of hate, violence, racial or other forms of intolerance that is discriminatory or the financial exploitation of a crime, (g) items that are considered obscene, (h) items that infringe or violate any copyright, trademark, right of publicity or privacy or any other proprietary right under the laws of any jurisdiction, (i) certain sexually oriented materials or services, (j) ammunition, firearms, or certain firearm parts or accessories, or (k) certain weapons or knives regulated under applicable law.

* relate to transactions that (a) show the personal information of third parties in violation of applicable law, (b) support pyramid or ponzi schemes, matrix programs, other "get rich quick" schemes or certain multi-level marketing programs, (c) are associated with purchases of annuities or lottery contracts, lay-away systems, off-shore banking or transactions to finance or refinance debts funded by a credit card, (d) are for the sale of certain items before the seller has control or possession of the item, (e) are by payment processors to collect payments on behalf of merchants, (f) are associated with the sale of traveler's checks or money orders, (g) involve currency exchanges or check cashing businesses, (h) involve certain credit repair, debt settlement services, credit transactions or insurance activities, or (i) involve offering or receiving payments for the purpose of bribery or corruption.

* involve the sales of products or services identified by government agencies to have a high likelihood of being fraudulent.

Look at what you need approval for: https://www.paypal.com/us/webapps/mpp/ua/acceptableuse-full

How's PorcFest going?

Oh, it's so absolutely lovely.

(Do we know each other? Or did you just read somewhere that I was going? Or just divine it from comments?)

Although this is my 4th, I haven't been to the last seven in a row. From 2014 to 2021, it has changed substantially in some ways (many more women and people of color, for example) and stayed almost identical in others (feral children starting businesses to be able to buy toys and ice cream, etc).

This is the first time I've had the bus, so we have a little more creature comfort than before.

Have you been before? I highly, highly recommend it. Hard to find a place to surround yourself with a higher concentration of loving / accepting energy.

It's as evil as you think the centralized authority is now or will be in the future. Some will also argue any entity having complete power over your life is inherently evil.

Its not. We use federated authorities and chains of trust all over the place.

But now its actually possible to have a distributed ledger so we're searching for problems to solve with this solution.

sure thing. we have invented something and now we are trying to apply it /s

how did the authorities and the chains of trust emerge in the first place? Is a system that uses a central authority more or less stable than a system that does not rely on the said authority?

Most consumer safety/encryption uses some kind of certificate chain with trusted roots. Its used from app installs to SSL to credit transactions.

Seems to be very efficient, cheap and effective.

nah. you're talking the tech. I'm talking about the actual authority.

What if someone decided that they would not issues you a cert? How would you do business at that point? But it's so efficient you says...

Also, it's efficient up to the point where you have to revoke a certificate. At that point the fun starts.

when you understand that a centralized authority decides what is okay and what is not okay and after that bans transactions that pay for the "not okay" items you will understand why a centralized authority is evil.

The magic keywords are "Prohibited Products and Services" Plug that into google + your favorite payment gateway.

Here are some samples:

https://www.nextpay.com/list-prohibited-industries.html

https://stripe.com/restricted-businesses

https://support.wix.com/en/article/wix-payments-prohibited-p...

http://support.worldpay.com/support/kb/gg/billdesk/content/p...

The problem with this argument is that governments still have jurisdiction over your decentralised blockchain, the developers, the miners, and anyone else involved in it. If you sincerely and seriously want to dismantle that power structure, that's fine, but please start in the right place, with government.

It's naive and ultimately fruitless to throw out all the good things that centralised payments bring (fast transactions, fraud control, etc etc) in the hope that you'll be able to get rid of a thing they don't actually have ultimate jurisdiction over (what is ok and not ok to buy).

yes, but no.

how would enforcing such jurisdiction even look like? you cannot take something off the blockchain.

Can you shutdown miners? sure. So what? The mining will happens somewhere else.

Can you really prohibit developers from working on the tech? If it comes down to this we're in full anarchy mode (and even at that point there are going to be people working on it).

Who said anything about throwing away all the good things centralized payments bring? How about we take a decentralized payments system and actually add those things (or even better, build a system that has them out of the box)

Nations can do much worse than just shutting down miners. Repeated 51% attacks would actually destroy a coins viability.

"He who can destroy a thing, can control a thing." - Paul Atreides/Frank Herbert

you're making a lot of assumptions here. what coin? different coins work in different ways.

Also, "51%" attacks have been known to be executed against "proper currencies, with backing of a central bank" https://www.investopedia.com/ask/answers/08/george-soros-ban...

> Can you really prohibit developers from working on the tech? If it comes down to this we're in full anarchy mode

I understand what you mean but that's not what anarchy the word means. It's actually the opposite and more in line with what most crypto people seem to be advocating for, the absence of government.

If you look at those lists, most of the items are not illegal. They mostly consist of things like gift cards, gambling, pornography, etc.

yup. you would expect items that are illegal to be prohibited. you would not expect travel checks to be banned. Travel Checks!!!

also, most payment processors ban guns, ammo and porn. that’s straight up un-American!!!

First, you're assuming everyone is out for the same thing. There are and will be centralized blockchains and services that meet specific needs. That's okay.

Second, it is not always a bad thing to have one fewer level of government, which is what centralization brings. A decentralized platform still operating within national regulations is like not having an HOA on your home. Not always a benefit, but usually, and especially over time.

I’m sorry, but what is the point if a centralised blockchain? The entire point of a blockchain is that it is decentralised!

Centralized and decentralized are far too broad a term to make a sweeping generalization at that level.

No, I'm not assuming that, I'm taking the arguments above about avoiding statist control of transactions at face value.

1. A centralised blockchain is a database with bad performance.

2. But that's my point - blockchain doesn't sidestep government and regulation as you and many proponents assume. In the short term maybe, while government catches up. In the long term, all your transactions are in public and can be inspected retrospectively, so good luck avoiding taxes or regulations with it if people actually started using it as a currency. It cannot reduce government because it does not replace government, it's aiming at the wrong target and just hand waving away problems of power which are central to control of money.

I won't presume to know if there's a real use case for #1 -- I agree that a centralized blockchain likely makes little sense, especially in this moment in time. But I would absolutely not be shocked if there is a use-case for "a database with bad performance" that's governed by one, or a group of, entities. A way to maintain transparency, vote on improvements, etc but only within, say, automotive, or whatever. There are only going to be growing use cases for data, ownership, privacy, and transparency use cases.

For #2, I think you're missing the point but apologize if you're not. However, I didn't say, and very few are saying, that blockchain sidesteps government and regulation. What I and many others are saying is that it sidesteps the additional layer of government that is a business entity. If you want to earn yield on BlockFi or Celsius for example, you are beholden to TOS and decisions in ways that are critically different than engaging similar functionality via a dapp.

My core point is that both can and likely will co-exist, because one is not inherently better than the other; the pros and cons will hit differently depending on the use case.

For some reason I was reminded of the ending of Dave Chappelle's old bit about Disney World: https://www.youtube.com/watch?v=mG7XikEENZ4

When pornhub wanted to start working with Visa, they had to shut down all pornhub non-verified accounts. Visa's terms.

As I recall, the issue was that it turned out that a lot of underage and non-consenting people were in videos on pornhub, and then MasterCard/visa said they would pull their support unless they fixed it.

I think a legitimate downside to blockchain is privacy. Sure, Stripe can (try to) prevent you from buying marijuana, but with crypto you’re required to announce that you’ve bought something from Dr. Chronic on the public ledger. Doesn’t that create an opportunity for discrimination/censorship/prosecution post-purchase? At least with Visa, you have a reasonable expectation that the transaction is private between you and the merchant. If you actually made the majority of your purchases on a blockchain, you’re publicizing a ton of information about yourself.

I have the same question. Usually the response is something about using randomly generated IDs/addresses with your “wallet” program managing all these pseudonyms and tying them to your actual identity for your convenience, but I don’t understand how that is any better than our current system where things just are private by nature. I don’t expect people to be okay with their purchase histories being public knowledge.

Monero solves this with cryptographic methods which are beyond me. But it works. Bitcoin indeed not so much - as soon as you can link a bitcoin address to somebody's identity it's over for them.

I'm no expert in crypto. But how would people know that your public key belongs to "you" ?

The other party in any transaction knows enough to "deliver" whatever you purchased. In the world where all your transactions happen on a blockchain, that's everyone from Amazon to the corner pizza shop.

> At least with Visa, you have a reasonable expectation that the transaction is private between you and the merchant.

Eh, not really: https://www.theverge.com/2018/8/30/17801880/google-mastercar...

Some purchase data being sold through brokers is not the same thing as a consumer buying space on the chain via gas prices to announce their purchases to the world, and then the entirety of the network burning resources to make that information available in perpetuity. It’s also something that’s easy to regulate.

It only seems like a problem to me in a monopolistic setting. If it's easy to go from visa to mastercard to your bank's debit card to venmo and easy for newcomers to enter, I don't see the problem. It's a big if :(

A central authority means not only trust but responsibility, and in turn risk. Why require so much responsibility when it is not necessary? The possible problems are not only malicious actions from the central authority but accidental actions and also susceptibility to malicious third parties. [Edit - problems]

I don't know much about STARKs, but I read that SNARKs has a problem with unbounded loops(variable number of iterations), also "break/continue" statements are problematic. Is it still true? Is there some research that will allow running code as is(no inefficient tricks like running maximum possible iterations)?

You can think of STARKS/SNARKS as proving computation, not by a program, but by a computational circuit. So the circuit size puts limits on the amount of computation. Recently, we see the introduction of recursive proof schemes (such as [1]), where part of the circuit may be verifying a proof of a much larger computation. Those can deal with certain forms of unbounded computation, such as verifying a blockchain history of arbitrarily many blocks.

[1] https://eprint.iacr.org/2021/370.pdf

No. This would be a tautological violation of zero-knowledge, so it will never be solved.

However, if all you care about is the verification proof, then yes, you can prove arbitrary recursions by providing the branch condition evaluations as part of the proof.

There were some interesting tidbits in the article, but the claims of very low TPS in blockchain are a bit out of date, to be honest. Things are changing fast in ethereum, cardano, etc.

Isn't the usual fix to take transactions off the Blockchain? Similarly to how public key crypto is made faster by encrypting a symmetric key?

You can’t store a blockchain in a ZK-snark/stark either. You can only verify it. So the transactions take place ‘off the blockchain’ here as well. The difference is that they can be verified no matter where they occurred.

What do you mean you can't store it?

The ‘succinct’ part of the acronym means that the data is not stored in the proof.

As has been the case for over 5 years.

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