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How to sign on ethereum a pdf like on this video?

I'm asking specifically about what happens at 00:40 where you have a user uploading the file and then it get stored and cryptographic signature is receive, how to create that functionality? https://vimeo.com/239155784

closed as unclear what you're asking by Achala Dissanayake, Briomkez, shane, Ismael, flygoing Nov 14 '18 at 2:31

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You want to include the hash of the files contents in your signed message to the blockhain

eg, on OSX terminal

$ md5 fileToNotarize.doc
MD5 (fileToNotarize.doc) = e789c8f38a10b495614ae07665c8db79

Then include the file hash with a transaction message to the blockchain

You also might try running through this tutorial on how to create a notary on the Ethereum blockchain

Also worth checking out Open Timestamps

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    Could you refer me to some tutorials/videos? I finish a few ethereum coding courses but still don’t know how to do that in practice – Damian Joniec Nov 11 '18 at 11:02
  • See edited answer – Vinnie James Nov 11 '18 at 16:19
  • In that video cryptographic signature is created automatically, user who uploads the file doesn't need to send the hash of the files contents, how to implement that kind of feature? – Damian Joniec Nov 13 '18 at 4:21

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