Stellar

Pre-requisite

You can access the code on Github:

zkFetch Stellar Example.

You will need a valid Stellar account seed phrase. Make sure you have enough funds to sign and send transactions. Freighter wallet is a convenient option.

This is the core part of the process, this code snippet shows how to fetch the latest XML price from CoinGecko's API in the form of a Reclaim proof. Once a proof is fetched, it gets written to /src/proof.json.

// Example URL to fetch the data from
const url =
  "https://api.coingecko.com/api/v3/simple/price?ids=stellar&vs_currencies=usd";
 
// Generate the proof
const proof = await reclaimClient.zkFetch(
  url,
  { method: "GET" },
  {
    responseMatches: [
      {
        type: "regex",
        value: '\\{"stellar":\\{"usd":(?<price>[\\d\\.]+)\\}\\}',
      },
    ],
  }
);

/src/utils.js

A couple of Reclaim-specific methods for parsing proofs.

 
// Returns the ECDSA signature recovery ID
export const getRecId = (signature) => {
  ...
}
 
// Removes the `0x` prefix from signature
export const formatSignature = (signature) => {
  ...
}
 
// Serializes the claim
export const getSerializedClaim = (proof) => {
  ...
}
 
// Returns the Keccak256 hash of the prefixed original message
export const getHash = (serializedClaim) => {
  ...
}

/src/verifyProof.js

The main script, it builds, signs, and sends the verification transaction to the network.

const tx = txBuilder
  .addOperation(
    contract.call(
      FUNCTION_NAME,
      ...[
        StellarSdk.nativeToScVal(message, { type: "bytes" }),
        StellarSdk.nativeToScVal(signature, { type: "bytes" }),
        StellarSdk.nativeToScVal(recId, { type: "u32" }),
      ]
    )
  )
  .setTimeout(StellarSdk.TimeoutInfinite)
  .build();

Try it

Clone the repo

git clone https://github.com/reclaimprotocol/zkfetch-stellar-example.git
 
cd zkfetch-stellar-example
 
npm install

Download ZK files

These are crucial for proof requesting, a device should have them locally to request Reclaim proofs.

node node_modules/@reclaimprotocol/zk-symmetric-crypto/lib/scripts/download-files

Add your seed phrase

Add the secret phrase of your signing account to .env.

SEEDPHRASE=

Request a proof

Change directory into /src and run:

node requestProof

Verify the proof

Once you have the proof in proof.json, run the following to verify on-chain:

node verifyProof