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There are multiple services of the kind (proofofexistence, poex, stampery, factom, originstamp, etc.), although some use private blockchains to store the data such as factom.
I'm curious on the fees, I saw on proofofexistence, the fee is fixed, 0.00025. It is not the fee you will paid for miners,
I am a little bit curious, what will happen the 0.00025btc?
Does ProofOfExistence will get some in those amount?
What this really is, is a method of inserting any kind of raw data in an immutable, decentralized and public ledger. This "data" can be anything you want because bitcoin doesn't care about the content of this special output. It is known as OP_RETURN outputs.
I see it is really amazing since the public ledger will never restrict what will be the data since the document is being hashed.
I also read about it, about the document integrity.
If you store a proof for your document and later re-upload it, the system will only recognize it if it is completely and fully the same document. The slightest change, and we'll recognize it is different, giving you the security that certified data can't be changed.
Once the hash will be the same or document will be the same as the uploaded, the system will notice it.