For this to be a chain, it would have to be published multiple times, each time containing references to previous blocks under the published hash.

Other than that I am pretty sure we can find many more examples. Hashing and publishing the hash is pretty popular way to prove timestamp of a secret without revealing the secret, yet. I did it myself a couple of times when I wanted to be able to prove later that I had a particular information before some specific time.

This statement could be made much more interesting and convincing if you provided some actual examples.

For example, I could post the hash "9712f2488fa00fc5b11b657995ac10c9" to Twitter and then after the prediction comes to pass, I can reveal that the hash was for the phrase "Pittsburgh Steelers will Defeat New Orleans Saints 30-21 in Super Bowl LIII", proving that I had some knowledge or prediction that I didn't want to reveal at the time of the prediction.

In practice, nobody is attending to anyone that closely, aside from a handful of public figures, and shenanigans like those you described might actually work to get someone more attention, only to fail once they have enough. That's why a publication mechanism that disallows deletions is desirable for such hashes.

"Instead of posting customer hashes to a public digital ledger, Surety creates a unique hash value of all the new seals added to the database each week and publishes this hash value in the New York Times. The hash is placed in a small ad in the Times classified section under the heading “Notices & Lost and Found” and has appeared once a week since 1995." ?

- Post a hash of a document to Twitter.

- Put a hash of a document in an ad in the NYT.

Quite similar.

https://twitter.com/gruber/status/991122089557004288?lang=en

There is even whole industry around the concept, it is called trusted timestamping: https://en.wikipedia.org/wiki/Trusted_timestamping

It basically works like this, you compute a hash of the document and send to some kind of service that will either publish your hash with the timestamp or will also sign the hash and the timestamp cryptographically without ever touching the document.

Later, you can refer somebody to the external service or let them examine the signature and the hash to prove that you were in possession of the information before certain date and time.

Chaining the hash values made it fundamentally impossible for any malicious actor to generate a notary certificate for a future document that would roll up and produce the correct super hash value that is woven into the chain.

> a copy of that seal and every other seal created by Surety’s customers is sent to the AbsoluteProof “universal registry database,” which is a “hash-chain” composed entirely of Surety customer seals. This creates an immutable record of all the Surety seals ever produced, so that it is impossible for the company or any malicious actor to modify a seal.

Another well known example of course is git (which slightly extends the definition to a directed acyclic graph).

Imagine if Google called certificate transparency blockchain? Journalists would lose their shit. Such an easy article to write. In fact, Google explicitly say on their website that they're kinda against the hype: http://www.certificate-transparency.org/general-transparency "These technologies are strongly related to the much-hyped blockchain. The reality, of course, is that there isn't a "the" blockchain, and that decentralisation is not always the answer. We are not making "the" blockchain, and we do not claim to support decentralisation."

I'll never forget my first job the business people wanted to investigate "the blockchain" and the yes men came up with a bunch of PoCs. I just asked "how is this different to Git?" Such an awkward moment.

Funny enough, "blockchain" as a term wasn't defined in the Bitcoin white paper at all.

A blockchain is a chain of blocks. Tautological, but the words mean something; it isn't just a name. If you hash blocks that contain hashes of previous blocks, you have a blockchain.

At most it might be argued that a centralized blockchain has no reason to exist, but I doubt that's true.

No, it doesn't work like that. "Blockchain" is understood to mean something and you can't decompose the compound word and say "well, here's a block. Oh, and here's a chain. I guess this is a block chain." Your description, e.g., applies to a Merkle tree [0], which git uses, and was published in 1979. But no one has ever or will ever call it a blockchain.

Is a Ford F-150 that's been lit on fire a firetruck? How much straw is in a strawberry?

[0] https://en.wikipedia.org/wiki/Merkle_tree

That might be a losing battle, but not sure the battle is over yet...

It wasn't- there's one mention of a "chain of blocks" in the white paper. The term "blockchain" appears to have been coined by Hal Finney.

All you need is 1) a reverse linked list of entries and 2) have the list be cryptographic in nature. Even git can be used for a blockchain since it uses a cryptographic hash for commits and can use GPG signing.

Validation, consensus and decentralizations are additional properties that you can add on top that make it useful for certain use cases.

This is one of the problems with the generic use of “blockchain”. People think you just need Merkle roots including previous blocks, like you do, but that’s useless and pointless without the rest.

That doesn't mean it isn't a blockchain. A inefficient or poor implementation of something is still an implementation of that thing.

>People think you just need Merkle roots including previous blocks, like you do, but that’s useless and pointless without the rest.

I'm well aware of the additional properties required to get it to behave like bitcoin or have cryptographic safety. But those are to my knowledge not a must-have for a blockchain nor defining characteristics.

As the name implies, it's a chain of blocks, the less obvious part is you link them with something cryptographic.

And just because Blockchain was first used and defined in Bitcoin doesn't mean the definition or methodology cannot be separated from Bitcoin, in fact, I consider it heavily separated from Bitcoin by now.

And again, just because they are factors in making Bitcoin work doesn't mean you need them to make a Blockchain.

A reasonable definition might be that a blockchain is a decentralized merkle tree.

(It's also possible that each published hash is just a brand new hash of the aggregate, but this seems somewhat less likely based on the wording.)

ETA: Looks like it's a chain, or rather a Merkle tree. From the horse's mouth: https://news.ycombinator.com/item?id=17865168

But I think we can agree that a Merkle chain like this would be sufficient for most of the things people are trying to use blockchains for recently, which certainly says something.

    - it's a distributed consensus system (often around "blocks", but e.g. iota is not)
    - it's a chain of hashes to prevent mutation (around "chains")

Very (very) few things benefit from distributed consensus IMO. And not all altcoins use blocks at all. So I tend to lean towards hash-chains. Publicly-verifiable immutability is useful in quite a lot of real-world scenarios.

A Digital Notary client application would submit a hash value (which in the early days was a combination of MD5 and SHA-1 but the system was very flexible in that it could upgrade the hash algos when more collision resistant versions became available) that would become part of a Merkle tree along with any other client submissions received in a short timeframe. The parent "top hash" node of the Merkle tree was then hashed with the the last value in a linked list referred to internally as the "super hash" chain to create a new end value in the chain.

The client application would receive a notary "certificate" containing all the values in the Merkle tree required to re-calculate the hash woven into the super hash chain along with the timestamp for the moment it became part of the chain. The client application could use this certificate at any time to electronically verify the veracity of any "document" (i.e., guarantee that the document existed in its exact form at a specific point in time.)

On a side note, the algorithms and implementation were successfully tested in court cases. (Some of Surety's customers used the system to timestamp millions of documents turned over in electronic legal discovery to ensure they were not tampered with by opposing counsel.)

The New York Times value was only significant in that if could be used to "manually" calculate the veracity of the notary certificate by hashing the super hash value it contained with all subsequent values in the super hash chain until it resulted in the hash value published in the Times. This "widely witnessed" approach made it impossible for an insider to collude with someone to generate a correct notary certificate retroactively by replacing the document with a forgery.

The blockchain technology used by crypto currencies is similar except for the tremendous amount of computation required to generate a "correct" hash value to close out a block and weave it into the chain.

Stuart Haber and Scott Stornetta deserve a lot of credit for creating this when were working for Bellcore. Two brilliant guys.

Here's the paper that started it all:

https://link.springer.com/article/10.1007/BF00196791

And a WSJ article describing the atmosphere in more detail:

https://www.wsj.com/articles/the-eureka-moment-that-made-bit...

It sounds like the Surity thing had "blocks" consisting of a week's worth of documents which got chained together and had their hash published irrevocably every week.

Without the subsequent invention and popularity of the specific implementation of the bitcoin blockchain - I don't think the slow/costly consensus "feature" could be considered a requirement to distinguish between "hash chains" and "block chains" like that.

(But I'm regularly on the losing side of nomenclature arguments - I'm still pissed at all the people who've decided they should call my non-autonomous quadcopters "drones"...)

Apparently we should call them quadpters because it's based on helicopter for which the ethymology is not heli + copter, but helico + pter, like in helicoidal and pterodactyl.

"Hey mister! Is that your drone?" "No kid, it's not a drone, it's a spinning dinosaur..."

A chain of hashed data dates back to Merkle himself, that’s what a Merkle tree is.

The entire point of bitcoin is distributed independent truth and that’s the entire point of a Blockchain.

https://bitcoin.org/bitcoin.pdf

It didn't use the word block in the sense of "to stop people from forging history".

A chain of hashed data dates back to Merkle himself, that’s what a Merkle tree is.

The entire point of bitcoin is distributed independent truth and that’s the entire point of a Blockchain.

Especially back in the 90s when generating crypto hashes wasn’t as easy for users.

So this is similar to notaries where the trust lies with a different party.

The killer app, I think, that made blockchain blockchain is the trustless nature.

Surety is certainly cool, but just a better version of putting a hash in a bank’s safety deposit box.

Also note the hash values sent to Surety were calculated on the end user's computer. Surety never sees the actual file being timestamped.

As for the safety deposit box metaphor, the Haber-Stornetta approach is akin to nailing the hash to a post in the town square.

I bet counterintelligence agencies are scraping social media and the web in order to see whether some travelers' identities are lacking in (or contradicted by) historical online documentation.

- Memorization of whole piece == Proof of work - You need lots of people to agree upon the story == 51 % of nodes - You can only append to the piece, because many others know and have memorized the piece so they will not agree to your version.

We'll start selling space in the coinbase field to real estate advertisers and escort services!

'The Times 03/Jan/2009: room to rent in 3br share house in The Mission, $2600/month+utilities'

However, the ex-CEO has mentioned that it only operates for existing customers (https://news.ycombinator.com/item?id=17865294), which conflicts with that view somewhat, so maybe this isn't an ad.

In any case; where can I view 1995 copies of NYT for free? :)

Every public library in the United States, if I'm not mistaken, and a large number of major libraries worldwide.

Mumbles something about equal opportunity open access and the bourgeois

Los Angeles Public Library, with a library card: https://www.lapl.org/new-york-times-digital (and you can apply for an e-card online for free: http://www.lapl.org/about-lapl/contact-us/e-card/e-card-regi...)

Kansas City Public Library, with a library card: https://www.kclibrary.org/blog/kc-unbound/how-read-back-issu...

Etc.

Summary: get a public library card, support the oh-so-terribly bourgeois public library system ;)

Redefining the nature of the technology to get away from the difficult reality of it isn’t effective in the end.