riptheworld

hace 4 añosdiscuss

No one is arguing that collision resistance and proof-of-work are the same things? The security of a PoW relies on collision resistance. Do you see the difference? It's subtle. Changing a block in the blockchain explicitly requires exploiting the collision-resistance property of a cryptographic hash. Why? BECAUSE YOU NEED TO PRODUCE VALID PROOFS OF WORK FROM INVALID TRANSACTIONS.

riptheworld

hace 4 añosdiscuss

This is literally proof of work. I don’t know what else I can do to explain that Bitcoin’s immutability property is directly parametrized by the security level in the PoW mechanism.

You are arguing that decentralization creates immutability. Decentralization has nothing to do with hashing.

riptheworld

hace 4 añosdiscuss

You are moving the goalposts. I described a mechanism that addresses link rot in the current NFT ecosystem. The hash-based method allows an owner to efficiently prove what content was associated with a rotted link with overwhelming probability. Using this basic building block, one could construct a process that allows an NFT owner to update the link stored on the blockchain.

If you are concerned with changing an NFT's content or debating philosophically about whether that should be allowed, I don't have an opinion. I don't own NFTs, nor am I convinced they will stick around. My point is that the NFT ecosystem will likely evolve to create technical solutions solving many of the problems mentioned in the article.

riptheworld

hace 4 añosdiscuss

> What would happen in practice? People would notice. A fork will be decided.

There's nothing in the Bitcoin protocol that explicitly prevents a longer and valid chain from being accepted. Forks happen every day where miners are competing to construct the longest accepted chain on the network (it's part of the protocol).

However, the difficulty in maliciously changing previous blocks in the Bitcoin blockchain is explicitly parameterized by the security level of the PoW mechanism. There are undergrad CS courses where this analysis is probably a homework problem.

In PoS, immutability is baked into the protocol since the block selection algorithm doesn't explicitly cause forking as it does in PoW based blockchains.

Decentralization creates trust that newly added blocks contain valid transactions, not to ensure that previous blocks don’t change. This is why the finality times of Bitcoin are strictly worse than the finality times of Algorand, or other PoS blockchains. Not because one network is more decentralized than the other, but because Bitcoin’s immutability property is hamstringed by the PoW security level.

EDIT: Anticipating your response requesting citations - here are the lecture notes from the "Foundations of Blockchain Systems" course at the University of Washington, Seattle [1]. From section 3.2, I quote:

"One property of the blockchain is immutability. This means that the chain cannot be changed given the last block in the chain. This is because it is difficult to find a hash of x that is equal to hash of y in computationally feasible time (collision-resistance). We add the qualifier “given the last block” because if we disagree on which is the last block, we may have problems. With distributed mining, there is a possibility of simultaneous mining, however these ties should be resolved quickly with proper tuning of parameters. Therefore, although we may not agree on the last block all of the time, all blocks will lead back to the genesis, starting block, and the large majority of the chain will be in agreement."

[1] https://ece595uwseattle.github.io/Scribe_notes_Lecture_3.pdf

riptheworld

hace 4 añosdiscuss

> But it is not PoW that makes the blockchain immutable. A lot of people are saying that, but they're wrong, I'm sorry.

You are incorrect. The proof of work mechanism is central to ensuring the immutability of the blockchain.

As a concrete example, suppose there are N blocks in the blockchain, and I want to change a transaction in the (N - 2) block. Obviously, this will change the hash of the (N - 1) and N-th blocks, so the decentralized network will not accept this arbitrary change.

However, if I can produce four PoWs corresponding to the new (N - 2), (N - 1), N, and (N + 1)th blocks, then I can convince the network to accept. Of course, I have to produce these four PoWs before the honest users on the network mine the next block at index (N + 1). This is extremely difficult by design. In theory, you would need the majority of the network’s computing power to carry out this attack.

In other words, the security level of the proof of work is directly related to the difficulty in modifying the blockchain.

riptheworld

hace 4 añosdiscuss

Correct. But this specifically solves the problem at hand. Rather than storing an entire image, video, etc. on the blockchain, you store a concise representation of that content. The collision-resistance property of a cryptographic hash ensures that the probability of finding two differing NFTs which hash to the same value is negligible. You would include the link in the token as well, but if the link ever rots, you have some way of proving what the original link pointed to.

riptheworld

hace 4 añosdiscuss

I agree that the current NFT ecosystem is a house of cards, e.g., the susceptibility of NFTs to link rot. That being said, I think the ecosystem will evolve to a having a more robust way of handling these things as it matures.

For example, rather than only storing a URL that points to the content, perhaps the token could also include a cryptographic hash of the original content? In the case of link rot, the owner could still provide evidence of ownership on the original content by proving that it hashes to the stored value.

There are probably better solutions as well (others have mentioned IPFS).

riptheworld

hace 4 añosdiscuss

Ahh I see! Thanks for the clarification!

riptheworld

hace 4 añosdiscuss

You could use existing trusted lending Institutions, no? Investors can loan their excess Bitcoin to a lending institution that pools Bitcoin from multiple investors and loans it out to borrowers? In return, the investor receives interest on the loaned amount when it is paid back in full? If the loan isn’t repaid, the courts get involved to seize other physical assets from the borrower (cars, homes, etc.).

In some sense, we would be back to having banks with the exception that the bank now exists solely as an investment vehicle.

I guess I’m struggling to see what barriers prevent crypto currencies from being used in traditional financing?

riptheworld

hace 4 añosdiscuss

You can trustlessly verify the entire Algorand history by verifying it yourself (same as Bitcoin). However, almost all blockchains (including Bitcoin) will suffer from this problem of longer and longer sync times, and so some bootstrapping solution is necessary.

riptheworld

hace 4 añosdiscuss

Bitcoin’s throughput is limited as a function of network security and network delay. It has nothing to do with making it easier for clients to sync with the current state. You can improve Bitcoin’s transaction rate in two ways:

1.) decrease mining difficulty, i.e., the amount of hashing required to produce a valid proof-of-work on average. This impacts the security of the network.

2.) increase the block size so you can fit more transactions into a single block. This negatively impacts network latency (and therefore scalability, as it increases the burden of propagating messages across the network).

To your question on Algorand: yes, new consensus participants can quickly and easily sync with the current state of the blockchain through fast catch-up [1], without any meaningful security degradation [2].

[1] https://youtu.be/BOnond-J3Zo

[2] https://eprint.iacr.org/2018/269.pdf

riptheworld

hace 4 añosdiscuss

Oh sheesh. No one said anything about Bitcoin miners voting. I was simply pointing out that centralization of mining power (which has already happened in Bitcoin) has essentially the same security impact as centralization of wealth in proof of stake consensus mechanisms.

> It would work the same way PayPal works with USD. Bitcoin payments simply don't need to happen on the blockchain. Similarly, I can buy gold in my brokerage account without any actual gold moving between warehouses.

This is a terrible idea.

riptheworld

hace 4 añosdiscuss

You’re confusing a layer 2 solution that provides separate (and weakened) transaction assurances than the Bitcoin protocol itself. This is evident in the fact that the lightning network suffers from security vulnerabilities (e.g., wormhole attack [1]) not present in the Layer 1 Bitcoin protocol.

This is not to say that the Lightning Network doesn't significantly improve the usability of Bitcoin as a currency. But it does so at the expense of security. A much better approach is to use a layer 1 solution that achieves scalability, security, and decentralization by default.

[1]https://eprint.iacr.org/2018/472.pdf

riptheworld

hace 4 añosdiscuss

[dead]

riptheworld

hace 4 añosdiscuss

I'm not sure what you mean when you say that Bitcoin can scale by using 3rd party payment providers? Any Bitcoin transaction will only ever be as fast as the underlying blockchain, which currently processes around seven transactions per second (last time I checked).

Of course proof of stake can be decentralized! I think what you mean is that it's not clear whether a widely adopted PoS based blockchain will end up centralizing power in the hands of a few whales. This is a legitimate concern; however, this threat is no different than the threat of centralization of computing power in Bitcoin. In Bitcoin, this isn't even a threat, it’s a reality!

I'll say it again: Bitcoin and Ethereum are not great currencies. There are altcoins that have far surpassed both of them in terms of achieving security, scalability, and decentralization simultaneously.

riptheworld

hace 4 añosdiscuss

Cryptocurrencies as a whole are an amazing innovation. It’s sad though to see people rushing to adopt things they don’t fully understand, and getting hurt as a result.

Bitcoin and Ethereum are pretty terrible currencies. Proof-of-work is a foundational idea in cryptography, but it’s much better suited for preventing mass email spam than it is as a consensus mechanism.

Not to mention how the cryptocurrency space is crowded with useless AltCoins. Unless you’re an expert in the space, its so hard to distinguish from true innovation and dummies just trying to get a piece of the pie. As a result, you have millions of people pushing things like Dogecoin and Shiba, and it ends up hurting real people.

The way I see it is this: a useful cryptocurrency needs 3 things:

(1) Security (2) Scalability (3) Decentralization

Almost all mainstream crypto fails at (2) miserably, and as a result end up failing at (3). High transaction fees, volatility, low throughput, and energy-intensive participation costs are all barriers to achieving actual utility.

riptheworld

hace 4 añosdiscuss

Perhaps I can convince you with a more philosophical argument.

Private communication is essential for freedom of speech. I may not speak freely with my friends or family if I believe that those conversations are easily accessible by the government. It's not that these conversations are inherently bad either; rather, I believe that people have a tendency to self-censor themselves depending on their audience. When the audience consists of an entity that has overwhelming influence on your life, I believe the potential for self-censorship is enormous.

Historically, many of the world’s greatest ideas were first discussed in private. Bold ideas were discussed in discreet locations, free from the threat of eavesdroppers out of fear of government recourse. Nowadays, technology has enabled people to communicate instantaneously with one another from thousands of miles away. Encryption enhances that capability by further allowing that communication to be private, fostering freedom of speech and the discussion of new ideas. It is really quite amazing when you think about it!

comments