Quote from: molecular on November 10, 2014, 09:36:54 PM

Quote from: dnaleor on November 10, 2014, 04:46:33 PM

Quote from: blossbloss on November 10, 2014, 02:43:29 PM

Quote from: Anon136 on November 10, 2014, 04:06:15 AM

Quote from: blossbloss on November 10, 2014, 04:01:25 AM

Can someone please provide a short step-by-step tutorial on how to use the Trezor to sign a hash of a document?
Thanks

From memory:

Click on the account that you want to use. Then near the top right you will see a sign and verify button. Click it. It will bring up 2 forms that you can fill out, sign and verify. The first field will be the message. Enter the message that you want to sign in the message field. The second field will be the address. begin typing the address that you want to use. it will detect the address you are entering and provide an option to fill out the rest of the address for you. Click sign. Now look at your trezor. It will ask you to confirm that you want to sign the message. Confirm that you do. Now enter your pin. Look back at the form page in your browser. you will see that the formerly empty signature box will now contain a series of characters. That is your digital signature.

Thanks. So this appears to be signing of messages disconnected to transactions. And it is signing with my private key.
Is there a way to include a message in a signed bitcoin transaction? In other words, can I include a SHA256 hash of a document and include it in a transaction that gets recorded on the blockchain? I think this can be done with some clients (although I do not know which ones can do it). But can it be accomplished from my Trezor?
Thanks

Molecular has designed a way to hash your document and create a private key out of it. You can send a very small amount of BTC to that address to "timestamp" it and proove you own that doc at a certain moment of time. Don't know if you are looking for that?

If you want the proove to be public, I think you can do the same by creating a public address out of the hash of the doc. But I never that that
(I used the method of Molecular to create a certificate of my Silver Casascius coin Wink

)

http://www.proofofexistence.com/ might be what you're looking for. At least it's very similar (identical in function, I think) to what dnaleor is describing and what I had implemented for proving cascascius coin existance. btw, no invention there: I just used the sha256 of the document as a private key (there's no conversion, both are just a 256 bit numbers), derived the matching bitcoin address and sent money to it. Adavantage: you can still move that money. Disadvantage: you can't read any 'message', just verify it has existed if you have it.

"Is there a way to include a message in a signed bitcoin transaction?" <- I'm not sure what to make of this. You can sign a transaction, you can sign a message. You can encode a message into a transaction.

Molecular,

Sorry for such a late reply to your response. Your proofofexistence site looks very interesting, but I have to admit I'm struggling making it work.

In the meantime I ran a test. I created a PDF file and generated its SHA256 hash as my private key. I used bitaddress.org's "wallet details" to generate the corresponding public address. I then sent a small fraction of a millibitcoin to that address to time stamp the transaction on the block. Now I can prove that the PDF document existed at the time of the transaction.

Is there something I'm missing?

Thanks.