# ScriptPubKey

You might not know that as far as the Blockchain is concerned, there is no such thing as a Bitcoin Address. Internally, the Bitcoin protocol identifies the recipient of Bitcoin by a **ScriptPubKey**.

![](https://236133742-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LL8tJvu-TV4ulp8gU1t%2F-LL8tOzX5dLCrxijS6s9%2F-LL8tRZjnzhpyuIocDEX%2FScriptPubKey.png?generation=1535616870796467\&alt=media)\
A **ScriptPubKey** may look like this:\
`OP_DUP OP_HASH160 14836dbe7f38c5ac3d49e8d790af808a4ee9edcf OP_EQUALVERIFY OP_CHECKSIG`

It is a short script that explains what conditions must be met to claim ownership of bitcoins. We will go into the types of operations in a **ScriptPubKey** as we move through the lessons of this book.

We are able to generate the ScriptPubKey from the Bitcoin Address. This is a step that all bitcoin clients do to translate the “human friendly” Bitcoin Address to the Blockchain readable address.

![](https://236133742-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LL8tJvu-TV4ulp8gU1t%2F-LL8tOzX5dLCrxijS6s9%2F-LL8tRZlUd24QyHDvBMl%2FBitcoinAddressToScriptPubKey.png?generation=1535616873959997\&alt=media)

```csharp
var publicKeyHash = new KeyId("14836dbe7f38c5ac3d49e8d790af808a4ee9edcf");

var testNetAddress = publicKeyHash.GetAddress(Network.TestNet);
var mainNetAddress = publicKeyHash.GetAddress(Network.Main);

Console.WriteLine(mainNetAddress.ScriptPubKey); // OP_DUP OP_HASH160 14836dbe7f38c5ac3d49e8d790af808a4ee9edcf OP_EQUALVERIFY OP_CHECKSIG
Console.WriteLine(testNetAddress.ScriptPubKey); // OP_DUP OP_HASH160 14836dbe7f38c5ac3d49e8d790af808a4ee9edcf OP_EQUALVERIFY OP_CHECKSIG
```

Notice the **ScriptPubKey** for testnet and mainnet address is the same?\
Notice the **ScriptPubKey** contains the hash of the public key?\
We will not go into the details yet, but note that the **ScriptPubKey** appears to have nothing to do with the Bitcoin Address, but it does show the hash of the public key.

Bitcoin Addresses are composed of a version byte which identifies the network where to use the address and the hash of a public key. So we can go backwards and generate a bitcoin address from the **ScriptPubKey** and the network identifier.

```csharp
var paymentScript = publicKeyHash.ScriptPubKey;
var sameMainNetAddress = paymentScript.GetDestinationAddress(Network.Main);
Console.WriteLine(mainNetAddress == sameMainNetAddress); // True
```

It is also possible to retrieve the hash from the **ScriptPubKey** and generate a Bitcoin Address from it:

```csharp
var samePublicKeyHash = (KeyId) paymentScript.GetDestination();
Console.WriteLine(publicKeyHash == samePublicKeyHash); // True
var sameMainNetAddress2 = new BitcoinPubKeyAddress(samePublicKeyHash, Network.Main);
Console.WriteLine(mainNetAddress == sameMainNetAddress2); // True
```

> **Note:** A ScriptPubKey does not necessarily contain the hashed public key(s) permitted to spend the bitcoin.

So now you understand the relationship between a Private Key, a Public Key, a Public Key Hash, a Bitcoin Address and a ScriptPubKey.

In the remainder of this book, we will exclusively use **ScriptPubKey**. A Bitcoin Address is only a user interface concept.


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