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Although I take slight issue with how you've worded it, I think I'm in agreement. I'll attempt to add clarification to the parts I find difficult to parse. Bl

Although I take slight issue with how you've worded it, I think I'm in agreement. I'll attempt to add clarification to the parts I find difficult to parse. Blockchains only ensure that coins are never spent twice. They make no attempts to ensure that coins are sent to the correct recipients. At the end of the block, they only care that debits are equal to credits. This can be confusing because the term "double spend" is also frequently used in cryptocurrency in the context of fraud prevention. In this context, you definitely do care that the coins get to the correct recipients but this concern is outside of the functional scope of the blockchain mechanism. Instead, fraud prevention is typically satisfied through additional code, adjacent to the "blockchain stuff", which establishes signaling networks and transaction inclusion criteria. They're very different mechanisms inside blockchain clients but, confusingly, they both make frequent use of the term "double spend".

bongobingo1 4y ago
> Blockchains only ensure that coins are never spent twice. They make no attempts to ensure that coins are sent to the correct recipients. At the end of the block, they only care that debits are equal to credits. I know the origin is tightly linked to bitcoin, but I feel like even this muddies the definition. Blockchains are not implicitly related to "coins", more facts? contracts? Maybe that's a useless nit to pick, or only useful in this thread where the GP was trying to layout where blockchains are useful (eg: distributed facts - that happen to often be wealth transfer). Or do I have it all wrong? I admit to not having much experience with them, but from the few random (non-btc) meet up groups talks I saw a decade ago, it was all about consensus more than anything. Ironically before the current NFT craze, the talk I remember most was one about using NFTs to authenticate stuff like (non-programatically-generated) album/artwork ownership and allowing users to resell in a second hand digital market. I assume you could build a mastodon like that distributes and "authenticates" posts via a blockchain - perhaps with terrible performance though.
- andrewaylett 4y ago
  The novelty of Blockchain is that it's a way for everyone to agree about which blocks are in the chain, such that we're confident everyone won't change their minds later. The content of the blocks is irrelevant to the consensus, in which every participant will independently pick the longest valid chain it can see. (In other words: yes, you've got it exactly right, but there are some details around incentives that tie creation of blocks to receiving some kind of benefit which mean that in practice someone will reduce things to money at some point)
- uncletammy 4y ago
  > Blockchains are not implicitly related to "coins" ... That was definitely an oversimplification, and a slightly wrong one at that. In bitcoin, there isn't actually a concept of "coins". Just transactions which spend numbered UTXOs. If I'm remembering correctly, the term "block chain" came from a conversation between Hal Finney and Satoshi Nakamoto about Bitcoin. If so, one could argue that it IS implicitly related to cryptocurrency. That being said, the underlying "block chain" data structure is just an alteration of a previously existing data structure called a Merkle Tree which has data blocks that can be used for things that are not transaction data. Blocks in a blockchain have a payload section reserved for transaction data. Theoretically you could put anything in the payload section but if you're calling the data structure a blockchain, people are probably going to expect transactions in it. > I assume you could build a mastodon like that distributes and "authenticates" posts via a blockchain - perhaps with terrible performance though. This has already been done many times actually and it's quite impressive. Basically, a cryptocurrency full node is modified to serve as a social client and an appropriate user interface is built on top. The mechanism by which cryptocurrency transactions are shared with other validating nodes is the very thing that keeps user's "streams" updated and in sync. It has some major drawbacks but performance doesn't have to be one of them. With UTXO based blockchains like bitcoin, the "mempool" portion of the client code receives transactions containing social data embedded within. This means they are able to show the social media content immediately upon it being sent, even if the transactions containing that data have yet to be included in a block. One problem though, is that like transaction data, the social data doesn't get "finalized" until it's included then mined in a block. So you'd be able to see the messages in your feed but the content might change ten minutes later after it's finalized. In my opinion, the Achilles heel of blockchain based social media is the Achilles heel of so many otherwise brilliant technologies: "What is someone uses it for child porn?" Otherwise, most of the other drawbacks can be dealt with.

bongobingo1 4y ago

> Blockchains only ensure that coins are never spent twice. They make no attempts to ensure that coins are sent to the correct recipients. At the end of the block, they only care that debits are equal to credits. I know the origin is tightly linked to bitcoin, but I feel like even this muddies the definition. Blockchains are not implicitly related to "coins", more facts? contracts? Maybe that's a useless nit to pick, or only useful in this thread where the GP was trying to layout where blockchains are useful (eg: distributed facts - that happen to often be wealth transfer). Or do I have it all wrong? I admit to not having much experience with them, but from the few random (non-btc) meet up groups talks I saw a decade ago, it was all about consensus more than anything. Ironically before the current NFT craze, the talk I remember most was one about using NFTs to authenticate stuff like (non-programatically-generated) album/artwork ownership and allowing users to resell in a second hand digital market. I assume you could build a mastodon like that distributes and "authenticates" posts via a blockchain - perhaps with terrible performance though.

andrewaylett 4y ago
The novelty of Blockchain is that it's a way for everyone to agree about which blocks are in the chain, such that we're confident everyone won't change their minds later. The content of the blocks is irrelevant to the consensus, in which every participant will independently pick the longest valid chain it can see. (In other words: yes, you've got it exactly right, but there are some details around incentives that tie creation of blocks to receiving some kind of benefit which mean that in practice someone will reduce things to money at some point)
uncletammy 4y ago
> Blockchains are not implicitly related to "coins" ... That was definitely an oversimplification, and a slightly wrong one at that. In bitcoin, there isn't actually a concept of "coins". Just transactions which spend numbered UTXOs. If I'm remembering correctly, the term "block chain" came from a conversation between Hal Finney and Satoshi Nakamoto about Bitcoin. If so, one could argue that it IS implicitly related to cryptocurrency. That being said, the underlying "block chain" data structure is just an alteration of a previously existing data structure called a Merkle Tree which has data blocks that can be used for things that are not transaction data. Blocks in a blockchain have a payload section reserved for transaction data. Theoretically you could put anything in the payload section but if you're calling the data structure a blockchain, people are probably going to expect transactions in it. > I assume you could build a mastodon like that distributes and "authenticates" posts via a blockchain - perhaps with terrible performance though. This has already been done many times actually and it's quite impressive. Basically, a cryptocurrency full node is modified to serve as a social client and an appropriate user interface is built on top. The mechanism by which cryptocurrency transactions are shared with other validating nodes is the very thing that keeps user's "streams" updated and in sync. It has some major drawbacks but performance doesn't have to be one of them. With UTXO based blockchains like bitcoin, the "mempool" portion of the client code receives transactions containing social data embedded within. This means they are able to show the social media content immediately upon it being sent, even if the transactions containing that data have yet to be included in a block. One problem though, is that like transaction data, the social data doesn't get "finalized" until it's included then mined in a block. So you'd be able to see the messages in your feed but the content might change ten minutes later after it's finalized. In my opinion, the Achilles heel of blockchain based social media is the Achilles heel of so many otherwise brilliant technologies: "What is someone uses it for child porn?" Otherwise, most of the other drawbacks can be dealt with.