@tianhr/open-attestation

Open Attestation

Attestation and notary framework for any document types on the blockchain.

OpenAttestation allows any entity to proof the existence of a document or a batch of documents. It makes use of smart contracts on the Ethereum blockchain to store cryptographic proofs of individual documents.

This repository allows you to batch the documents to obtain the merkle root of the batch to be committed to the blockchain. It also allows you to verify the signature of the document wrapped using the OpenAttestation framework.

Installation

npm i @govtechsg/open-attestation

API References

Wrapping documents

wrapDocuments takes in an array of document and returns the batched documents. Each document must be valid regarding the version of the schema used (see below) It computes the merkle root of the batch and appends the signature to each document. This merkle root can be published on the blockchain and queried against to prove the provenance of the document issued this way.

This function accept a second optional parameter to specify the version of open-attestation you want to use. By default, open-attestation will use schema 2.0.

The wrapDocument function is identical but accept only one document.

import { wrapDocuments } from "@govtechsg/open-attestation";
const document = {
  id: "SERIAL_NUMBER_123",
  $template: {
    name: "CUSTOM_TEMPLATE",
    type: "EMBEDDED_RENDERER",
    url: "https://localhost:3000/renderer",
  },
  issuers: [
    {
      name: "DEMO STORE",
      tokenRegistry: "0x9178F546D3FF57D7A6352bD61B80cCCD46199C2d",
      identityProof: {
        type: "DNS-TXT",
        location: "tradetrust.io",
      },
    },
  ],
  recipient: {
    name: "Recipient Name",
  },
  unknownKey: "unknownValue",
  attachments: [
    {
      filename: "sample.pdf",
      type: "application/pdf",
      data: "BASE64_ENCODED_FILE",
    },
  ],
};

wrappedDocuments = wrapDocuments([document, { ...document, id: "different id" }]); // will ensure document is valid regarding open-attestation 2.0 schema
console.log(wrappedDocuments);
wrappedDocuments = wrapDocuments([document, { ...document, id: "different id" }], { version: "open-attestation/3.0" }); // will ensure document is valid regarding open-attestation 3.0 schema
console.log(wrappedDocuments);

Sign a document

signDocument takes a wrapped document, as well as a public/private key pair or an Ethers.js Signer. The method will sign the merkle root from the wrapped document, happened the signature to the document and return it. Currently, it supports the following sign algorithm:

• Secp256k1VerificationKey2018

Example with public/private key pair

import { signDocument, SUPPORTED_SIGNING_ALGORITHM } from "@govtechsg/open-attestation";
await signDocument(wrappedV2Document, SUPPORTED_SIGNING_ALGORITHM.Secp256k1VerificationKey2018, {
  public: "did:ethr:0xE712878f6E8d5d4F9e87E10DA604F9cB564C9a89#controller",
  private: "0x497c85ed89f1874ba37532d1e33519aba15bd533cdcb90774cc497bfe3cde655",
});

Example with signer

import { signDocument, SUPPORTED_SIGNING_ALGORITHM } from "@govtechsg/open-attestation";
import { Wallet } from "ethers";

const wallet = Wallet.fromMnemonic("tourist quality multiply denial diary height funny calm disease buddy speed gold");
const { proof } = await signDocument(
  wrappedDocumentV2,
  SUPPORTED_SIGNING_ALGORITHM.Secp256k1VerificationKey2018,
  wallet
);

Validate schema of document

validateSchema checks that the document conforms to open attestation data structure.

import { validateSchema } from "@govtechsg/open-attestation";
const validatedSchema = validateSchema(wrappedDocument);
console.log(validatedSchema);

Verify signature of document

verifysignature checks that the signature of the document corresponds to the actual content in the document. In addition, it checks that the target hash (hash of the document content), is part of the set of documents wrapped in the batch using the proofs.

Note that this method does not check against the blockchain or any registry if this document has been published. The merkle root of this document need to be checked against a publicly accessible document store (can be a smart contract on the blockchain).

import { verifySignature } from "@govtechsg/open-attestation";
const verified = verifySignature(wrappedDocument);
console.log(verified);

Retrieving document data

getData returns the original data stored in the document, in a readable format.

import { getData } from "@govtechsg/open-attestation";
const data = getData(wrappedDocument);
console.log(data);

Utils

import { utils } from "@govtechsg/open-attestation";
utils.isWrappedV3Document(document);

• isWrappedV2Document type guard for wrapped v2 document
• isSignedWrappedV2Document type guard for signed v2 document
• isSignedWrappedV3Document type guard for signed v3 document
• isWrappedV3Document type guard for wrapped v3 document
• diagnose tool to find out why a document is not a valid open attestation file (wrapped or signed document)

Obfuscating data

obfuscateDocument removes a key-value pair from the document's data section, without causing the file hash to change. This can be used to generate a new document containing a subset of the original data, yet allow the recipient to proof the provenance of the document.

const newData = obfuscateDocument(wrappedDocument, "key1");
console.log(newData);

Test

npm run test

vc-test-suite

You can run the vc-test-suite against open-attestation by running npm run test:vc. This command will:

• clone https://github.com/w3c/vc-test-suite.git
• copy the local configuration (vc-test-suite-config.json) into the cloned repository
• install the latest version of @govtechsg/open-attestation-cli
• monkey patch open-attestation in @govtechsg/open-attestation-cli. That means that the current version of the project will be built and replace the one installed with @govtechsg/open-attestation-cli.

Local debug

In the event you face a problem with one test and want to debug locally:

1. Ensure the folder vc-test-suite is available from the root of the project. If that's not the case, run npm run test:vc first.
2. Open runVcTest.sh and update install_vc_test_suite=true to install_vc_test_suite=false. This line will help to preserve the vc-test-suite folder untouched.

You can now debug from the vc-test-suite folder the way you need it.