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have read a little about blockchains and found there is lot of blockchain npm libraries available.
How can I take benefit of the bitcoin blockchain to authenticate documents : to obtain a proof a document has not been alterated ot changed.
Any clues, suggestions, ideas and remarks are welcome.
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I'd suggest taking a look at chainpoint.org (Full disclosure, I'm the VP Engineering at Tierion, the creators of the Chainpoint open standard).
Chainpoint currently uses the Tierion HashAPI, and you can submit hashes to the API for free. We'll provide you with a proof that you can store alongside your original document. We have a Javascript library you can use to access the HashAPI.
We are getting ready to release a brand new v3 version of Chainpoint that has some great new features that we've announced (and some we haven't). Chainpoint v3 will be fully open source (clients and server), and free to use. I think you'll find it solves your needs quite nicely and we'd love your feedback.
Glenn
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You can make a transaction with the hash (of the document) as a comment. That would proof that the file existed at that time.
It doesn't however magically proof that a document hasn't been changed. Once you get the document, you can store the hash on the blockchain, then to check if it hasn't been changed, you can retrieve the hash and check if the current version of the file still hashes to the same value.
There will most likely be a library for this, I wouldn't know the name of a specific one however.
ok: and how to store the hash on the blockchain ? Any nodejs library or sample to recommend ? – yarek – 2017-07-05T22:53:22.150
Check out https://opentimestamps.org/
2What do you mean "a document has not been altered or changed"? What's the difference between altering or changing a document and just having two different documents? Do you want to prove that a particular document is the documented someone signed or agreed to? Do you want to prove that a particular documented existed at a particular time? It's not clear what you're actually trying to do. – David Schwartz – 2017-07-06T03:23:18.567