Does Proof-of-Stake consensus require a blockchain?

Question

In a proof-of-work blockchain, the validity of the network is ensured by the hashes of each block pointing to the previous block. A "block on its own" would not be very trustworthy and, without all the CPU-work required to mine a block, it seems like there would be no reason to have a blockchain because the entire chain could be regenerated at zero cost.

So a network that didn't rely on proof-of-work at all would see little need for a blockchain, right? They could simply have a list of transactions organized by index, timestamp or some other type of organization. I don't see what value the blockchain (array with hash and pointer to previous block) provides over a traditional "ordered list of transactions" if there is no proof-of-work.

Answer 1

There is confusion, Proof of work (and other proof of ...) is a consensus method. It allows a network of peers to agree on a common history. It doesn't mean we have to store the information in a blockchain. An analogy would be, the first one who finds a solution to this math problem gets to choose the next movie we're going to watch.

Storing the data in a blockchain allows immutability. If we just agree on adding a transaction at address x, and store them as is, there is no way to check is the information has been tampered with. Someone arrives later and asks what was the last movie we watched, you would have to ask everyone present at the time if you want to be sure that they're not lying. With a blockchain (a kind of signed chain array), you can check easily if they are lying or not.

Answer 2

Your notion that only proof of work uses a hash pointer to the previous block is wrong. This is a characteristic of blockchain , not the used consensus algorithm.

The hash pointer guarantees immutability of the previous block, if the data in the block is changed so does the hash.

The consensus type is merely a way to decide on how the network agrees which transactions should be added. If in proof of stake you vote wrong, you lose your stake. If you calculate the wrong proof of work you just spent a ton of time and electricity for nothing.

Proof of stake is not better than proof of work, it just works different.

What you describe as an "ordered list of timestamped transactions" is another characteristic of blockchain. The transactions are just grouped together in a merkle tree rather than broadcast one by one.

Answer 3

From what I understand, although this may be incorrect, the proof of work for each block has no effect on the validity of the information. The block has a digital signature from the person who forged it, which is factored into the calculation of the block's hash, which is included in the next block, and so on and so forth.

The only thing proof of work does, from a validity perspective, is to say once someone creates a block, "Find a hash of this format." The reasoning for this isn't for some sort of validity check; it is simply a way to delay the network.

Without Proof of Work, as more processing power joins the network, the block time would go down. If the block time is too low, then the chain will constantly fork, which leads to issues with dropped transactions and more.

The only thing proof of work does is act as a way to slow down the generation of blocks by the network as a whole.

Proof of stake will still have the same digital signatures on blocks, as with the current system, ensuring their validity. However, instead of the block time being determined by an increasingly difficult puzzle, the stakers will simply wait until it is their "turn" to create a block.

So, recap, Proof of Work is honestly nothing more than a way to delay blocks.

As such, your understanding of a blockchain requiring PoW to be a blockchain is flawed. PoS would require a blockchain, but PoW is completely irrelevant to that fact.