# Code Snippet

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

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

```rust
use crate::lib_loader::generate_zkpass_proof;

let zkpass_proof_token = unsafe {
    generate_zkpass_proof(credentials, user_data_tokens, dvr_token)
};
```

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

1. `credentials` : Get yours API key and secret at `https://portal.ssi.id`
2. `user_data_tokens` :  stringified signed users data.
3. `dvr_token` : signed Dvr query.

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

```rust
use crate::lib_loader::verify_zkpass_proof;
use dvr_types::ExpectedDvrMetadataFfi;

//
// Step 1: Create the expected metadata object.
//
let expected_metadata = ExpectedDvrMetadataFfi {
    ttl: some_ttl,
    dvr: expected_dvr_cstring.as_ptr(),
    user_data_verifying_keys: user_data_requests_slice.as_ptr(),
    user_data_verifying_keys_len: user_data_requests_slice.len() as u64,
};

//
// Step 2: Call verify proof.
//
let result = unsafe {
    verify_zkpass_proof(&service_url, zkvm, zkpass_proof_token, expected_metadata)
};
```

This code snippet verifies a zkPass proof token. Components :

1. `zkpass_proof_token` : check [Generate Proof](#generate-proof) section for more details.
2. `expected_metadata` :  this is the expected metadata of the dvr.
3. `zkvm`: zkvm used to generate proof, currently we only support `r0`.
4. `service_url` : you can use `https://playground-zkpass.ssi.id` , or use your own endpoint if you deploy zkPass on your own server.

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

```rust
use crate::lib_loader::generate_user_data_token;

let user_data_token = unsafe {
    generate_user_data_token(signing_key, &data.to_string())
};
```

This code snippet generate user data token. Components :

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

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

```rust
use crate::lib_loader::generate_query_token;

let dvr_token = unsafe { generate_query_token(signing_key, dvr_data) };
```

This code snippet generate DVR token. Components :

1. `signing_key` : a private key used to sign dvr.
2. `dvr_data` : Dvr data to sign.


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