GitHub - bitcoinjs/bitcoinjs-message

Bitcoin is wonderful: Verifying a bitcoin signed message - quick tutorial

Message signing and verification is an often overlooked and powerful feature built right into bitcoin.
Any decent bitcoin client/wallet includes message signing and verification.
There are lots of use cases for message signing and verification, but for the sake of this tutorial lets make up a simple scenario:
Let's say we've made arrangements to buy 2,500 Bits from a vendor on Local Bitcoins.
We are a little wary of meeting the seller because we have never met before, and would like some proof that he at least has the Bitcoin we are planing to buy.
We can not just simply ask for an address that holds greater than 2,500 Bits, the seller could simply pick any address with greater then that balance and claim it was their own, like 17rr2mq3WgZFurjDvFWEPQ3iAm2iuWHJd9 (coincidentally an address I hold the key for).
We need definitive proof they control the private key for the address 17rr2mq3WgZFurjDvFWEPQ3iAm2iuWHJd9 before we can know, with no doubt, they at least have access to the bitcoins we plan to buy.
To get this proof we can ask the seller to sign a message with the address they claim to own (17rr2mq3WgZFurjDvFWEPQ3iAm2iuWHJd9) which contains the 2,500 Bits we plan to buy, to be safe we can even provide the message.
These 2,500 bits are going to be purchased by CoinCadence 
We send the above message to the seller and ask him to sign it with the address 17rr2mq3WgZFurjDvFWEPQ3iAm2iuWHJd9.
The seller replies with the following signature:
Hxrox3By8i7lEJoHxS/+GfwLtn9BfFk5BXMrqgCNhe1ZXSXuT6F9DfLLY4HPG/vQ/qcGJy03dIqZY459r7hiGMk= 
We now have the 3 items we need to verify that the seller does indeed control such a massive amount of bitcoin.
To validate (or invalidate) the signature fire up your favorite clients message verification, or head over to the Chain Query Bitcoin API's verify message endpoint:
http://chainquery.com/bitcoin-api/verifymessage
Cut and paste our 3 items into the form and execute the command (be careful to copy exactly as any change will invalidate the signature).
In this example the signature is true, meaning we can trust that the seller at least has the coins available, if the result had been false I'd very suspect of meeting a stranger in person with my cash.
Try it yourself! Use your wallet to sign a message of your choosing, and verify the signature at http://chainquery.com/bitcoin-api/verifymessage
If you find your choice of wallet is not capable of signing messages, consider a new wallet ;)
Edited for formatting
submitted by CoinCadence to Bitcoin [link] [comments]

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*bitcoin-cli help verifymessage. verifymessage "address" "signature" "message" Verify a signed message Arguments: 1. "address" (string, required) The bitcoin address to use for the signature. 2. "signature" (string, required) The signature provided by the signer in base 64 encoding (see signmessage). 3. "message" (string, required) The message that was signed. Result: truefalse (boolean) If ... Using the Blockchain.info API to verify bitcoin signatures in C#. Ask Question Asked 4 years, 1 month ago. Viewed 717 times 1. I am building a website and want to verify the user's bitcoin signature using the blockchain.info api method (https://blockchain ... This site aims to provide the docs you need to understand Bitcoin and start building Bitcoin-based applications. The are a few ways to verify messages in a browser or, obviously, with most clients, but I was using the blockchain.info api as a client and it didn't support verifymessage. I have literally installed bitcoind on my server so I can verify a few signed messages a week automatically, and then figured someone else may have the same problem. But I ... This site aims to provide the docs you need to understand Bitcoin and start building Bitcoin-based applications.

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Mobile number for sms verification

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