# Code Snippet

This section describes how we use the zkPass SDK in our demo code

#### <mark style="color:orange;">Generate Proof</mark>

```typescript
import { DvrModuleClient } from "@zkpass/dvr-client-ts";

...

// Step 1: Instantiate DvrModuleClient
const dvrModuleClient = new DvrModuleClient({
      baseUrl: SERVICE_URL,
      apiKey: API_KEY,
      secretApiKey: API_SECRET,
    });

// Step 2: Call the DVR module client's callDvrGenerateZkPassProof
const zkPassProof = dvrModuleClient.callDvrGenerateZkPassProof(
      JSON.stringify(userDataToken),
      dvrToken
    );
```

This code snippet generates a zkPass proof. It requires 3 parameters:

1. `SERVICE_URL` : you can use `https://playground-zkpass.ssi.id` , or use your own endpoint if you deploy zkPass on your own server.
2. `API_KEY` & `API_SECRET`: Get yours at `https://portal.ssi.id`
3. `userDataToken` :  check [Generate User Data Token](https://docs.ssi.id/zkpass/v/zkpass-developers-guide/sdk-tutorial/quick-start/typescript-node.js-linux#generate-user-data-token) section for more details.
4. `dvrToken` : check [Generate DVR Token](https://docs.ssi.id/zkpass/v/zkpass-developers-guide/sdk-tutorial/quick-start/typescript-node.js-linux#generate-dvr-token) section for more details.

#### <mark style="color:orange;">Verify Proof</mark>

```typescript
import { DvrModuleClient, extractPayload } from "@zkpass/dvr-client-ts";

const dvrPayload = extractPayload(dvrToken);
...

// Step 1: Instantiate the zkPassClient object.
const dvrModuleClient = new DvrModuleClient({
      baseUrl: ZKPASS_SERVICE_URL,
      apiKey: API_KEY,
      secretApiKey: API_SECRET,
    });

// Step 2: Create the expected metadata
const expectedMetadata = {
      dvr: JSON.stringify(dvrPayload),
      ttl: EXPECTED_DVR_TTL,
      user_data_verifying_keys: userDataVerifyingKeys,
    };

// Step 3: Call zkPassClient.verifyZkPassProof to verify the proof.
const proofOutput = dvrModuleClient.callDvrVerifyZkPassProof(
      ZKPASS_ZKVM,
      zkPassProofToken,
      expectedMetadata
    );
```

This code snippet verifies a zkPass proof token. Components :

1. `zkPassProofToken` : check [Generate Proof](https://docs.ssi.id/zkpass/v/zkpass-developers-guide/sdk-tutorial/quick-start/typescript-node.js-linux#generate-proof) section for more details.
2. `expectedMetadata` :  this is the expected metadata of the dvr.
3. `dvrPayload`: the dvr payload extracted from Dvr token.

#### <mark style="color:orange;">Generate User Data Token</mark>

```typescript
import { DvrModuleClient } from "@zkpass/dvr-client-ts";

...

// Step 1: Instantiate DvrModuleClient
const dvrModuleClient = new DvrModuleClient({
      baseUrl: SERVICE_URL,
      apiKey: API_KEY,
      secretApiKey: API_SECRET,
    });
//
// Step 2: Call the DVR module client's callDvrGenerateUserDataToken
//         This is to digitally-sign the user data.
const userDataToken = dvrModuleClient.callDvrGenerateUserDataToken(
      signingKey,
      JSON.stringify(data)
    );
```

This code snippet generate user data token. Components :

1. `signingKey` : a private key used to sign user data.
2. `data` : user data in JSON format.

#### <mark style="color:orange;">Generate DVR Token</mark>

```typescript
import { DvrModuleClient } from "@zkpass/dvr-client-ts";

...

// Step 1: Initiate DvrModuleClient
const dvrModuleClient = new DvrModuleClient({
      baseUrl: SERVICE_URL,
      apiKey: API_KEY,
      secretApiKey: API_SECRET,
    });

// Step 2: Generate Dvr query token
const dvrToken = dvrModuleClient.callDvrGenerateQueryToken(
      signingKey,
      dvrData
    );
```

This code snippet generate DVR token. Components :

1. `signingKey` : a private key used to sign dvr.
2. `dvrData` : Dvr data to sign.


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