Proof of Existence

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Proof of Existence is an online service that verifies the existence of computer files as of a specific time via timestamped transactions in the bitcoin blockchain.

It was launched in 2013 as an open source project. It was developed by Manuel Araoz and Esteban Ordano.

On May 21, 2017, the "Blockchain Notary Service" was acquired by Canaan.

"I'm really happy to close this deal with Canaan. First and foremost because they understand blockchain technology," Araoz said in a statement. "They've been around for years, and they expend hard dollars to build the chips that secure the blockchain. I'm looking forward to enhancing the product, and exploring other blockchain services."


On May 24, 2013 reporter Jeremy Kirk from IDG News Service wrote that "It's essentially a notary public service on the Internet, an inexpensive way of using Bitcoin's distributed computing power to allow people to verify that a document existed at a certain point in time." On May 8, 2014 reporter Daniel Cawrey from CoinDesk wrote that the service "is an example of how the power of this new technology can have applications far beyond the world of finance, in this case, giving a glimpse of how bitcoin could one day have a substantial impact in the fields of intellectual property and law." However, a more accurate time can be calculated from the surrounding blocks if increased precision is necessary.


  • Digital Sign Agreement without revealing actual content.
  • Demonstrating data ownership without revealing actual data.
  • Document time stamping.
  • Proving ownership
  • Checking for document integrity

See Also on BitcoinWiki[edit]