How the Known Traveller Digital Identity concept lets travellers share verified facts selectively, and how it differs from the standard Digital Travel Credential.
How Known Traveller Digital Identity fits together
The problem: a journey made of identity checks
A single international trip can involve seventeen or more steps where somebody checks who you are: visa application, booking, airline check-in, luggage drop, security, immigration on departure, airline gate, arrival immigration, customs, hotel check-in and more. Each checkpoint asks for a similar set of documents and each keeps its own copy of your data.
The KTDI idea is to let a traveller build up a set of verified facts in advance, hold them in an app on their own device, and share only what each checkpoint needs. A hotel does not need your full passport record; a border agency does not need your loyalty-programme status.
How KTDI works
The concept pairs a traveller’s phone with biometric authentication. Credentials are held as digital attestations issued by trusted parties, which might be a government passport agency, an airline, a bank or a hotel. The traveller can then present combinations of these to different parties.
Three ideas do most of the work. Multiple attestations mean claims can come from government and non-government sources, so a verified payment history or hotel booking can sit alongside a passport check. Selective disclosure means the traveller shares only the necessary claims. Specific revocation means an issuer can cancel one attestation it issued without affecting the others.
To check that a credential is genuine and unrevoked, verifiers use a decentralised public key infrastructure, so no single intermediary has to be consulted each time. A distributed ledger acts as the shared registry for those keys and revocation records.
KTDI and the Digital Travel Credential
KTDI is often compared with the Digital Travel Credential (DTC) promoted through the International Civil Aviation Organization, which stores virtual credentials on a mobile device or in the cloud, unlocked by biometrics, for document-free travel between participating countries. The briefing material highlights these differences:
| KTDI | Digital Travel Credential (DTC) | |
|---|---|---|
| Claims | Several verified attestations from government or non-government issuers | One verified attestation from a government issuer |
| Disclosure | Selective disclosure of claims | All-or-nothing disclosure |
| Revocation | An issuer can revoke one specific attestation it issued | Revoking a Country Signing Certificate, which typically affects thousands of identities |
| Trust infrastructure | Decentralised public key infrastructure, so no intermediary is needed to check validity or revocation | Centralised public key infrastructure that must be consulted |
Neither approach is better in every setting. The DTC fits neatly into the existing system of national passport authorities, which is a strength for governments that want continuity. KTDI aims for flexibility and privacy, with a trade-off in complexity.
Choosing the platform
The KTDI pilot evaluated five platforms: Hyperledger Indy, R3 Corda, uPort, Sovrin and Hyperledger Fabric, comparing them on decentralisation, standards support and scalability. Hyperledger Indy, which was purpose-built for decentralised identity, was chosen as the foundation. The lesson generalises: a general-purpose blockchain is not automatically the best identity layer.
The standards underneath
Interoperability comes from standards, and the briefing lists the key ones. At the ISO level, committee ISO/TC 307 on blockchain and distributed ledger technologies was created in 2016 and had 44 participating countries and one published standard, with ten more under development, when the briefing was written. It has working groups on terminology, security, privacy and identity, smart contracts, governance and use cases.
On the web side, W3C’s Decentralized Identifiers give people and organisations self-managed identifiers, and Verifiable Credentials provide a standard way to express claims. Existing building blocks include OpenID Connect, OAuth 2.0 and JSON Web Tokens, plus biometric standards from ISO/IEC JTC 1/SC 37 and the US NIST digital identity guidelines (SP 800-63).
The briefing’s reasoning for all this is practical: standards mean multiple vendors can supply interchangeable products, adoption spreads faster, integrators carry less risk and users avoid lock-in.
Questions worth asking
Who gets to be an issuer, and who decides which issuers are trusted? How does a traveller recover credentials if a phone is lost? What stops verifiers from demanding more data than they need? These governance questions matter as much as the cryptography, and they echo the UK report’s point that both technical code and legal code must be rigorous (see our UK ledger report summary).
Sources
- Known Traveller Digital Identity: Specifications Guidance. World Economic Forum, March 2020.
- KTDI Briefing. Hyperledger (briefing slides on identity and standards), undated.
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