# Quick Start

Let's quickly demonstrate with a NodeJS project to see HollowDB in action. 

## Setup

Open up your favorite terminal and/or IDE and create a new directory for our fresh project:

```bash
mkdir hollowdb-example
cd hollowdb-example
```

Install HollowDB & Warp Contracts packages:

```bash
yarn add hollowdb warp-contracts
```

Finally, create yourself an Arweave wallet at <https://arweave.app/> or use an existing one if you have. Download your wallet (which will be a JSON file) and put it as `wallet.json` in the current directory.

Create a new file called `index.js`. Prepare the code as follows:

```javascript
const { SDK } = require("hollowdb");
const { WarpFactory } = require("warp-contracts");
const fs = require("fs");
 
async function main() {
  // we will write our code here...
}

main(); 
```

## Instantiating HollowDB

To instantiate HollowDB SDK, we need to provide a signer object (that will be our wallet), a Warp instance and a contract transaction id to specify which smart contract we are connecting to. Let's do just that!

Write the following code within your `main` function:

```javascript
// read your wallet
const wallet = JSON.parse(fs.readFileSync("./wallet.json").toString());

// use an existing contract
// to deploy your own, read "Contract Operations" section :)
const contractTxId = "_eVfQYDOLpd-0QX0yt7RV2CXE5D9U0otCz9BNBiJMYY";

// we will use Mainnet
const warp = WarpFactory.forMainnet();
  
// create the SDK!
const sdk = new SDK(wallet, contractTxId, warp);
```

## Generating proofs & computing the key

The contract we are connecting to in this example uses zero-knowledge proofs to update keys. So, we can very much get a value at some key, or put a new key-value pair; but when it comes to updating them we will need to generate proofs!

We can use [HollowDB Prover](https://docs.hollowdb.xyz/zero-knowledge-proofs/hollowdb-prover) for this:

```javascript
const { Prover, computeKey } = require("hollowdb-prover");
```

## Getting & Setting keys

It's time to put everything to use! Here is what we will do:

* define a secret that is related to our key
* put some value to that key
* update that value using a zero-knowledge proof

First, we will define our `secret`, which can be anything that you'd like. We can say `secret=2023` for this example; although, if you really care about the secret staying that way, you should make a longer secret :)

Let's go back to writing code within our `main` function:

```javascript
const secret = BigInt("0xDEADBEEF"); // or something that only YOU know :)
const key = computeKey(secret);
console.log("Key:", key);
```

We have created our key just like that. Everyone expect you will see that huge number, but only you know that the key was created with the number `2023`.&#x20;

Let's put the string `"hello world"` to this key.

```javascript
// put a value
await sdk.put(key, "hello world");
// get that value
console.log(await sdk.get(key));
```

As simple as that. Now, let's update our value at this key to `"bye bye world"`. To do that, we will need to create a zero-knowledge proof that we know the secret (that is `2023`) which belongs to this key. We have written the Prover utility just for that!

To create the prover object, we need two things:

* [WASM circuit](https://github.com/firstbatchxyz/hollowdb/blob/master/config/circuits/hollow-authz-groth16/hollow-authz.wasm)
* [Prover key](https://github.com/firstbatchxyz/hollowdb/blob/master/config/circuits/hollow-authz-groth16/prover_key.zkey)

Download these files and add them to the project directory. Then, create the prover as follows:

```javascript
const prover = new Prover("./hollow-authz.wasm", "./prover_key.zkey", "groth16");
```

To generate the proof, we provide our secret, along with the current value & next value:

```javascript
const { proof } = await prover.prove(secret, "hello world", "seeya world");
```

We can now update our value using the SDK.

```javascript
// update value
await sdk.update(key, "bye bye world", proof);
// get the new value
console.log(await sdk.get(key));
```

That is it! Our final `index.js` looks like the following:

```javascript
const { SDK } = require("hollowdb");
const { WarpFactory } = require("warp-contracts");
const { Prover, computeKey } = require("hollowdb-prover");
const fs = require("fs");

async function main() {
  // read your wallet
  const wallet = JSON.parse(fs.readFileSync("./wallet.json").toString());

  // use an existing contract
  // to deploy your own, read "Contract Operations" section :)
  const contractTxId = "_eVfQYDOLpd-0QX0yt7RV2CXE5D9U0otCz9BNBiJMYY";

  // we will use Mainnet
  const warp = WarpFactory.forMainnet();

  // create the SDK!
  const sdk = new SDK(wallet, contractTxId, warp);

  const secret = BigInt(2023);
  const key = computeKey(secret);
  console.log("Key:", key);

  console.log("Putting a value...");
  // put a value
  await sdk.put(key, "hello world");
  // get that value
  console.log(await sdk.get(key));

  console.log("Generating a proof for update...");
  // create the prover
  const prover = new Prover("./hollow-authz.wasm", "./prover_key.zkey", "groth16");
  // generate proof
  const { proof } = await prover.prove(secret, "hello world", "seeya world");

  console.log("Updating the value...");
  // update value
  await sdk.update(key, "bye bye world", proof);
  // get the new value
  console.log(await sdk.get(key));
}

main();
```

You can check out the contract we are using at [SonAR](https://sonar.warp.cc/#/app/contract/_eVfQYDOLpd-0QX0yt7RV2CXE5D9U0otCz9BNBiJMYY#), where you will also be able to see your transactions.

## Further reading

To learn more about using HollowDB, continue with the usage section:

{% content-ref url="hollowdb/usage" %}
[usage](https://docs.hollowdb.xyz/hollowdb/usage)
{% endcontent-ref %}

To learn more about zero-knowledge proofs & the zk-circuit used in HollowDB, check out the background section:

{% content-ref url="zero-knowledge-proofs/background" %}
[background](https://docs.hollowdb.xyz/zero-knowledge-proofs/background)
{% endcontent-ref %}

Or, you can directly jump to application use-cases:

{% content-ref url="use-cases/overview" %}
[overview](https://docs.hollowdb.xyz/use-cases/overview)
{% endcontent-ref %}