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GDPR Art. 5(1)(c) (opens in a new tab) · Immigration documents

A government body checking a single fact about someone's immigration status has to collect the whole document that proves it.

NG Docu Vault keeps documents encrypted off-chain and proves single facts with zero-knowledge proofs.

Status: Delivered in April 2025. The code is published on GitHub under the AGPL-3.0 licence.

Operating constraint

An immigration authority checking a single fact about a person's status needs evidence it can verify without receiving the whole document. Immigration files carry personal details well beyond that fact, and the system had to work across EU, US and Canadian document standards.

How it was built.

Encrypted documents stay off-chain in IPFS; hashes and zero-knowledge proofs support verification without disclosing the file.
Project
NG Docu Vault
Programme
NGI Sargasso, Open Call 5
Delivered
April 2025
Jurisdictions
EU, US and Canadian document standards
Domain partner
An immigration-law practice
Timeline
Delivered · April 2025

Decisions, and the obligation or standard each one meets.

  1. Only transaction hashes are anchored on-chain. Files are held off-chain.

    MeetsGDPR Art. 5(1)(f) integrity, and EDPB Guidelines 02/2025 v2.0 on blockchain, which treats an on-chain hash as pseudonymised personal data. No document is written to the chain; only a minimised, pseudonymous hash is, and a verifier can use it to confirm a file is unaltered. (opens in a new tab)

  2. Documents are encrypted with AES-256 on the client before IPFS custody.

    MeetsGDPR Art. 32(1)(a) names encryption among the security measures for personal data. (opens in a new tab)

  3. Self-sovereign identity with zero-knowledge proofs.

    MeetsGDPR Art. 5(1)(c) data minimisation. A government body verifies the credential and does not receive the document. (opens in a new tab)

Design response

NG Docu Vault combines wallet sign-in, a document vault and an identity layer. A holder signs in with an Ethereum wallet through Sign-In with Ethereum and registers a document, which is encrypted with AES-256 and pinned to IPFS off the chain while the DocuVault contract records its hash. The holder can share a document, grant consent and let a verifier check it. Decentralised-identifier contracts handle registration, authentication, issuance and verification, and zero-knowledge circuits prove an age threshold, a document hash or a FHIR field without revealing the underlying data. Self-sovereign identity lets an authority confirm a credential without receiving the document behind it.

Result

An authority can verify a person's credential while the document stays encrypted off the chain. NG Docu Vault was delivered under NGI Sargasso, Open Call 5, and its application, API and contract code are published under the AGPL-3.0 licence.

The record behind this engagement.

Funded under NGI Sargasso, Open Call 5.

View evidence — NG Docu Vault (opens in a new tab)

Licence: AGPL-3.0

Tell us what you're building and the regulation it has to meet.

You will speak with one of the two founders.