Data Holder

The Data Holder should follow four steps to integrate with zkPass:

1. Retrieving the DVR from the Proof Verifier

2. Retrieving the user data from the Data Issuer

3. Generating the ZkPass Proof from the two inputs: DVR and user data

4. Sending the ZkPass Proof to the Proof Verifier for the proof verification

Sample Implementation

Sample codes for the Data Holder implementation follow. Each step is explained in detail in the subsections. The code is also available on the zkpass-sdk repo, as shown here:

https://github.com/gl-zkPass/zkpass-sdk/blob/main/rust/zkpass-demo/src/data_holder.rs

/*
 * data_holder.rs
 * Simulating the Data Holder process for the zkPass Demo
 *
 * ---
 * References:
 *   https://docs.ssi.id/zkpass/zkpass-developers-guide/privacy-apps/dvr/dvr-client-roles/data-holder
 * ---
 * Copyright (c) 2024 PT Darta Media Indonesia. All rights reserved.
 */
use crate::{
    data_issuer::DataIssuer,
    proof_verifier::ProofVerifier,
    lib_loader::generate_zkpass_proof,
};
use client_utils::interface::PrivacyAppCredentialsFfi;
use std::{ collections::HashMap, time::Instant, ffi::CString };
use tracing::info;
use zkpass_query_types::OutputReader;

pub struct DataHolder;

impl DataHolder {
    ///
    /// Starts the Data Holder process.
    ///
    pub async fn start(&self, zkvm: &str, data_files: HashMap<String, String>, dvr_file: &str) {
        //
        //  Get the user data from the data issuer
        //
        let data_issuer = DataIssuer;
        let user_data_tokens_map = data_issuer.get_user_data_tokens(data_files);
        let user_data_tags_list: Vec<&String> = user_data_tokens_map.keys().collect();
        let user_data_tokens = serde_json::to_string(&user_data_tokens_map).unwrap();

        //
        //  Get the dvr from the verifier
        //
        let mut proof_verifier = ProofVerifier::default();
        let dvr_token = proof_verifier.get_dvr_token(zkvm, dvr_file, user_data_tags_list);

        let zkpass_service_url = std::env
            ::var("ZKPASS_URL")
            .unwrap_or("https://staging-zkpass.ssi.id".to_string());
        info!("service_url={}", zkpass_service_url);
        println!("\n#### starting zkpass proof generation...");
        let start = Instant::now();

        //
        //  Data Holder's integration points with the zkpass-client SDK library
        //

        //
        // Step 1: Call the dvr client's generate_zk_pass_proof
        //         to get the zkpass_proof_token.
        //
        let credentials = self.generate_credential();
        let zkpass_proof_token = unsafe {
            generate_zkpass_proof(credentials, user_data_tokens, dvr_token)
        };

        let duration = start.elapsed();
        println!("#### generation completed [time={:?}]", duration);

        //
        //  Step 2: Send the zkpass_proof_token to the Proof Verifier
        //          to get the proof verified and retrieve the query result.
        //
        let query_result = proof_verifier.verify_zkpass_proof(zkvm, &zkpass_proof_token).await;

        println!("json-result={}", OutputReader::pretty_print(&query_result));
        let output_reader = OutputReader::from_json(&query_result).unwrap();
        println!(">> output list:");
        for entry in output_reader.enumerate() {
            println!("key={}, value={:?}", entry.key, entry.val);
        }
        println!("<< end of list");

        let val = output_reader.find_bool("result").unwrap();
        println!("the query result is {}", val);
    }

    ///
    /// Generates the privacy app credentials.
    ///
    fn generate_credential(&self) -> PrivacyAppCredentialsFfi {
        let base_url = std::env
            ::var("ZKPASS_URL")
            .unwrap_or("https://staging-zkpass.ssi.id".to_string());
        let api_key = std::env::var("API_KEY").expect("API_KEY must be set");
        let secret_api_key = std::env::var("SECRET_API_KEY").expect("SECRET_API_KEY must be set");

        PrivacyAppCredentialsFfi {
            base_url: CString::new(base_url).unwrap().into_raw(),
            api_key: CString::new(api_key).unwrap().into_raw(),
            secret_api_key: CString::new(secret_api_key).unwrap().into_raw(),
        }
    }
}