# Proof of ownership as an authentication method

> \[[2016.05.02](https://www.youtube.com/watch?v=dZNtbAFnr-0)] My name is Craig Wright and I am about to demonstrate a signing of a message with the public key that is associated with the first transaction ever done in Bitcoin.

```csharp
var bitcoinPrivateKey = new BitcoinSecret("XXXXXXXXXXXXXXXXXXXXXXXXXX", Network.Main);

var message = "I am Craig Wright";
string signature = bitcoinPrivateKey.PrivateKey.SignMessage(message);
Console.WriteLine(signature); // IN5v9+3HGW1q71OqQ1boSZTm0/DCiMpI8E4JB1nD67TCbIVMRk/e3KrTT9GvOuu3NGN0w8R2lWOV2cxnBp+Of8c=
```

Was that so hard?

You may remember Craig Wright, who really wanted us to believe he is Satoshi Nakamoto.\
He had successfully convinced a handful of influential Bitcoin people and journalists with some social engineering.\
Fortunately digital signatures do not work that way.\
Let's quickly find on the [Internet](https://en.bitcoin.it/wiki/Genesis_block) the first ever bitcoin address, associated with the genesis block: [1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa](https://blockchain.info/address/1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa) and verify his claim:

```csharp
var message = "I am Craig Wright";
var signature = "IN5v9+3HGW1q71OqQ1boSZTm0/DCiMpI8E4JB1nD67TCbIVMRk/e3KrTT9GvOuu3NGN0w8R2lWOV2cxnBp+Of8c=";

var address = new BitcoinPubKeyAddress("1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa", Network.Main);
bool isCraigWrightSatoshi = address.VerifyMessage(message, signature);

Console.WriteLine("Is Craig Wright Satoshi? " + isCraigWrightSatoshi);
```

SPOILER ALERT! The bool will be false.

Here is how you prove you are the owner of an address without moving coins:

**Address:**\
[1KF8kUVHK42XzgcmJF4Lxz4wcL5WDL97PB](https://blockchain.info/address/1KF8kUVHK42XzgcmJF4Lxz4wcL5WDL97PB)\
**Message:**\
Nicolas Dorier Book Funding Address\
**Signature:**\
H1jiXPzun3rXi0N9v9R5fAWrfEae9WPmlL5DJBj1eTStSvpKdRR8Io6/uT9tGH/3OnzG6ym5yytuWoA9ahkC3dQ=

This constitutes proof that Nicolas Dorier owns the private key of the book.\
**Exercise:** Verify that Nicolas sensei is not lying!

## Sidenote

Do you know how PGP works? Pretty similar, right?\
Maybe this can be the foundation of a more user friendly PGP alternative.\
Please build it on top of NBitcoin :-)


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