Information Passports — Technical Description

Introduction

The official version of this document is on GitHub.

An Information Passport is a signed digital document that makes some claim, for example “So and so was Vaccinated against COVID-19 on a certain date”. If the signature matches the public key of the digital document, the document is Verified. If the Claim made in the document checks against a set of (use-defined) rules and the “fingerprint” of the public key is known, we say the document is Validated.

A Vaccination Passport is an Information Passport that provides digital proof of a Vaccination. A Test Passport is an Information Passport that provides digital proof of some test having been performed.

Information Passports are built on the following technology stack. It’s helpful to be familiar with these technologies, but deep knowledge is not required:

  • JSON — The People’s Data Serialization
  • Schema — a shared vocabulary for describing things on the Internet and in the real world.
  • JSON-LD — encodes semantic data, e.g. Schema data, in JSON
  • Verifiable Credentials — a W3C working group for digitally encoding e.g. a Driver’s Licence
  • Canonical JSON — for creating the payload for signing
  • JSON Web Signing — an IETF standard for creating digital signatures and encoding them in a way that is compatible with JSON
  • X.509 Cryptography — a venerable standard for public key cryptography, the backbone of e.g. TLS / HTTPS / the secure web.
  • ISO 8601 — for all dates and times
  • Decentralized Identifier friendly — not really a core technology, but useful in concept
  • Standard Webstack — HTTP and TCP/IP. No core dependency on blockchains or distributed ledgers.

As our goals include being simple to implement and simple to understand, we constrain how these standards are used to get the functionality we need but no more. For example, all Information Passports are JSON-LD, but you do not need to use the JSON-LD libraries to work with Information Passports, just JSON.

  • It is easy for humans to read and write.
  • It is easy for machines to parse and generate. These two points should be familiar, they are the design ideals of JSON.
  • Open Source Implementation — our inspiration is the early web, where any reasonably skilled technologist could pick up it up and do something useful. Our open source reference implementation is on GitHub at information-passport and a reference sample website is at information-passport-website.
  • Non-creepy — minimize the potential for personal information leakage and the need for data centralization
  • Secure — obviously
  • Revokable — e.g. in the case of security breaches or fraudulently issued credentials
  • Renounceable — e.g. having a URL to a passport won’t guarantee it will verify or validate in the future
  • Localized / Internationalized — passports need to work across multiple cultures and languages
  • Semantic — data should Linked Data friendly. In particular, Schema should be the jumping off point for data definitions
  • Standards Based — standing on the shoulders of giants, etc. etc.
  • Minimalistic — define the least to do the job, and no more: for example, we do not define whether the mobile phone number of a Passport holder needs to be recorded
  • Open Ended — if you need a Passport system that requires e.g. a mobile phone number, it should be straight-forward to build on this standard
  • Paper Friendly — an Information Passport should work as well by presenting a piece of paper as by doing something “digital”
  • Non-app — it should not require an app to be installed on a smart phone. As per above, it should not even require a smart phone! However, if there are app-based passport solutions / “wallets” (there are several underway) this standard will likely provide an excellent data source.
  • ID Entry friendly — ideally, it would be simple to enter some sort of Passport identifier into a website, like you do with e.g. a Credit Card.

Our reference example is David Janes received a COVID-19 Vaccination at the General Hospital. Sunrise Long Term Care cannot let him enter the building unless he follows the rules set by Western Health.

This follows the Verifiable Credentials ecosystem model.

  • Subject — the entity a Claim is being made about; in the example, “David Janes”
  • Issuer — the entity making the Claim; in the example, this would most likely be “General Hospital” but it could be e.g. the government agency that controls General Hospital.
  • Verifier — is the entity checking the Claim; in the example, “Sunrise Long Term Care”
  • Verifiable Data Registry — is the entity that holds the rules and the X.509 public keys that will be accepted by the Verifier; in this example, it’s “Western Health”

The Standard

Issuers will have a X.509 Private / Public Keypair.

The Private Key obviously belongs to the Issuer and must be a closely held secret.

The Public Key must either:

  • must be issued by the Verifiable Data Registry, as part of a Certificate Chain
  • or be registered with the Verifiable Data Registry (less preferable)

In either case, the Verifiable Data Registry will provide a list of Public Key Fingerprints that it recognizes as valid. This will be used in the Validation process, described below.

When using a Certificate Chain, the number of Fingerprints that have to be published is greatly reduced, as only the “root” Fingerprints need be published.

The Certificate Chain MUST be in the Leaf to Root order, There is no requirement for the Root and Intermediate(s) Certificates to be there, but the order most be correct.

The Certificate Chain should be published on the web as a URI.

Signing and Verifying

The Signing and Verification Algorithm is defined in full here.

To summarize, Signing involves:

  • start with some claim, e.g. “David Janes been given the COVID19 Vaccine”
  • encode as a QName Compacted JSON-LD record with data encoded in Schema format.
  • sign using the ConsensasRSA2021 standard, which encodes the signature in the JSON and — although being JSON-LD friendly — does not require JSON-LD, just JSON Web Signatures.

The Signed document is a JSON-LD compatible document that includes:

  • the original claim
  • the proof, which includes
  • the signature
  • when the claim was signed
  • where the Public Key Certificate Chain can be found on the web

Verification involves basically the same process as Signing, and then using the rules of JSON Web Signing with the Public Key to see if the signature is valid. Mathematically, only the entity with access to the private key can generate a document that validates against the Public Key.

Validation

Validation consists of two parts:

  • ensuring the Public Key is recognized
  • ensuring the Claim itself is a recognized and valid

The second part — is the Claim recognized and valid — is basically business logic, and it is outside of scope of this document.

The first part is a list of Public Keys. The exact payload for delivering this is open, but likely will be a simple JSON document with some framing (and potentially digitally signed also)

Entrepreneur. Technologist. CTO / Co-founder of Consensas.com; founder Discover Anywhere Mobile.