README.md

Certificate Verification

Certificate verification on the Internet Computer is the process of verifying that a canister's response to a query call has gone through consensus with other replicas hosting the same canister.

This package partially encapsulates the protocol for such verification. It performs the following actions:

• Decoding of the certificate and the canister provided tree
• Verification of the certificate's root of trust
• Verification of the certificate's delegations (if any)
• Decoding of a canister provided merkle tree
• Verification that the canister provided merkle tree's root hash matches the canister's certified data

Usage

In the following example, canister is an actor created with @dfinity/agent-js for a canister with the following candid:

type certified_response = record {
  "data" : nat32;
  "certificate" : blob;
  "witness" : blob;
};

service : {
  "get_data" : () -> (certified_response) query;
};

Check ic-certification for details on how to create certificate and witness inside your canister.

calculateDataHash is a userland provided function that can calculate the hash of the data returned from the canister. This must be calculated in the same way on the canister and the frontend.

const { data, certificate, witness } = await canister.get_data();

const tree = await verifyCertification({
  canisterId: Principal.fromText(canisterId),
  encodedCertificate: new Uint8Array(certificate).buffer,
  encodedTree: new Uint8Array(witness).buffer,
  rootKey: agent.rootKey,
  maxCertificateTimeOffsetMs: 50000,
});

const treeDataHash = lookup_path(['count'], tree);
const responseDataHash = calculateDataHash(data);

if (treeDataHash !== responseDataHash) {
  // The data returned from the canister does not match the certified data.
}

Examples

See the certified counter example for a full e2e example of how to create a certification and verify it using this package.