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inkyoto 3 days ago

> No one knew what “blockchain” was, how it worked, or what could be used for.

Not the blockchain itself, but the concept of an immutable, append only, tamper-proof ledger underpinning it is a very useful one in many contexts where the question of authenticity of datasets arises – the blockchain has given us a ledger database.

The ledger database is more than just a hash as it also provides a cryptographic proof that the data is authentic via hash chaining, no ability to delete or modify a record, and the entire change history of any record. All these properties make the ledger databases very useful in many contexts, especially the ones where official documents are involved.

Ekaros 2 days ago | parent | next [-]

I often feel that immutability is very much over-rated and goes against real word. Lot of legal system is build on reverting things. Thus things being harder to revert is not actually desirable property.

inkyoto 2 days ago | parent [-]

No. Official and legal records detest the in place changes, love a full history of changes, and also love to walk the entire history of changes back. You do not have to convince me, you can talk to the state auditors instead to get their perspective.

Consider two simple and common scenarios (there are more): citizenship certificates and the recognition of prior learning.

1. Citizenship – the person with the name of Joanna Doe in the birth certificate was issued with a citizenship certificate in the same name. As time goes by, Joanna Doe changes the legal name to Joanna Smith; the citizenship certificate is reissued with the new legal name. We do not want to truly update the existing record in the citizenship database and simply change Doe -> Smith as it will create a mismatch with the name in the birth certificate. If we use a ledger database, an update operation will create a new revision of the same record and all subsequent simple query operations will return the latest updated revision with the new name. The first revision, however, will still be retained in the table's cryptographically verifiable audit/history log.

Why should we care? Because Joanna Smith can accidentally throw their new citizenship certificate away and later they will want to renew their passport (or the driver's licence). The citizenship certificate may be restored[0] by presenting the birth certificate in the original name and the current or expired passport, but the passport is in the new name. From a random system's point of view, Joanna Doe and Joanna Smith are two distinct individuals with no apparent link between them. However, the ledger database can provide proof that it is the same person indeed because the unabridged history of name changes is available, it can be queried and relied upon.

2. Recognition of prior learning – a person has been awarded a degree at institution A. Credits from Institution A contributed to a degree at Institution B. The degree at B is revoked due to issues with source evidence (i.e. Institution A). The ledger database makes such ripple effects deterministic – a revocation event at B triggers rules that re-evaluate dependent awards and enrolments at partners, with a verifiable trail of who was notified and when. If Institution A later corrects its own records, Institution B and downstream bodies can attach a superseding record rather than overwrite, preserving full lineage. The entire drama unfolded will always be available.

2½. Recognition of prior learning (bonus) – an employer verified the degree on the hiring date. Months later it is revoked. The employer can present a ledger proof that, on the hiring date, the credential existed and was valid. It reduces dispute risk and supports fair-use decisions such as probation reviews rather than immediate termination.

All this stuff is very real and the right tech stack (i.e. the ledger DB) reduces the complexity tremendously.

[0] Different jurisdictions have different rules but the procedure is more or less similar amongst them.

kstrauser 3 days ago | parent | prev | next [-]

For all that stuff, I like the blockchain implementation known as "git".

inkyoto 3 days ago | parent [-]

I have heard an argument for git before, and it is a viable fit for some use cases.

The problem, however, stems from the fact that the git commit history can be modified, which automatically disqualifies git in many other use cases, e.g. official government-issued documents, financial records, recognition of prior learning, and similar – anywhere where the entire, unabridged history of records is required.

kstrauser 3 days ago | parent [-]

It can't without destroying every subsequent commits' digest, unless you find a way to generate commits with identical SHA digests.

inkyoto 3 days ago | parent [-]

There is no such a thing as «subsequent commits» in git.

Commits in git are non-linear and form a tree[0][1]. A commit can be easily deleted without affecting the rest of the tree. If the git commit represent a subtree with branches dangling off it, deleting such a commit will delete the entire subtree. Commits can also be moved around, detached and re-attached to other commits.

[0] https://www.baeldung.com/ops/git-objects-empty-directory#2-g...

[1] https://www.baeldung.com/ops/git-trees-commit-tree-navigatio...

Blockingto 2 days ago | parent | prev | next [-]

Blockchain did not give us that.

It only moved the goal post.

As long as you can't guarauntee that the data you put onto a blockchain is trustworth in the first place, whatever you put on a blockchain is not 'tamper-proof'.

Therefore the ONLY thing you can handle on a blockchain 'tamper-proof' is stuff only existing on the blockchain itself. Which means basically nothing.

And there is a second goal post which was moved: the ignorance about a blockchain being 'tamper-proof'. 51% attack are real, you don't know if a country just owns and controls a lot of nodes and the latest rumor: NSA was involved in blockchain creation. You don't know if something is hidden in the system which gives one entity an edge over others.

phonon 3 days ago | parent | prev | next [-]

Yes, that kind of database was so in demand, the AWS version, "Amazon Quantum Ledger Database" was hugely successful. Oh wait, it was a flop and is being shut down....

inkyoto 3 days ago | parent [-]

No snark required. Whatever the reason for discontinuing QLDB was, it has been replaced with the pgAudit[0] Postgres extension in AWS. I did look into using QLDB for a project involving the management of financial records about 4 years ago and found it to be a somewhat unwieldy to use document database.

Demand for ledger databases is strong in the government and elsewhere where compliance is a non-negotiable. Microsoft have their own on the offer[1] as well.

[0] https://www.pgaudit.org/

[1] https://learn.microsoft.com/en-us/sql/relational-databases/s...

mvdtnz 2 days ago | parent | prev | next [-]

> but the concept of an immutable, append only, tamper-proof ledger underpinning it is a very useful one

Which is why blockchains have become such a ubiquitous technology. They're literally everywhere. Can't swing a cat without hitting a blockchain nowadays.

inkyoto a day ago | parent [-]

You have responded to the wrong comment. I have presented a case that concerns ledger databases, not the blockchains. If one doesn't understand the difference between the two, it is probably a good idea to refrain from chiming in.

3 days ago | parent | prev [-]
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