Verifiable Data Registry

A VDR provides a cryptographically secure root of trust for Decentralized Identifiers (DIDs). It stores DID Documents—which contain public keys and service endpoints—on a distributed ledger, enabling any entity to resolve a DID to its current state without a central authority. This anchors digital identity to a persistent, verifiable system.

• Example: The Sovrin Network uses a permissioned ledger as its VDR to publish Hyperledger Indy DIDs.

The VDR acts as a public repository for the schemas and credential definitions that structure Verifiable Credentials. Schemas define the data model (e.g., firstName, issueDate), while definitions bind that schema to a specific issuer's cryptographic key. Publishing these structures on the VDR allows verifiers to independently validate the format and origin of any presented credential.

• Key Benefit: Enforces semantic interoperability across different issuers and verifiers.

Every write operation to the VDR—such as creating a DID, updating a key, or revoking a credential—is recorded as an immutable transaction. This creates a cryptographic audit trail that provides tamper-evident provenance for all managed data. Entities can cryptographically verify the entire history of a DID or credential status, ensuring no record has been altered after the fact.

To manage credential lifecycle, VDRs support revocation registries. Instead of storing credentials themselves, the VDR holds cryptographic accumulators or lists that indicate if a credential is still valid. A verifier checks this registry status to confirm the credential hasn't been revoked by its issuer, enabling privacy-preserving revocation without revealing the credential's contents.

• Mechanism: Often implemented via revocation registries or status lists on the ledger.

VDRs can operate under different governance models to suit various trust requirements.

• Permissioned/Private: Ledgers like Hyperledger Indy or Corda where a consortium of known entities operates the nodes. Used for enterprise and regulated environments where transaction semantics and validator identity matter.
• Permissionless/Public: Leveraging networks like Ethereum or Bitcoin as a VDR, where anyone can participate. Favored for maximum censorship resistance and decentralization.

Effective VDRs implement open W3C standards to ensure system-wide interoperability. Key standards include:

• W3C Decentralized Identifiers (DID) 1.0: For identifier syntax and resolution.
• W3C Verifiable Credentials Data Model 1.1: For credential structure and proof formats.
• DID Methods: Specification (e.g., did:ethr:, did:indy:) defining how a particular VDR creates, resolves, and updates DIDs.

VDRs serve as the foundational layer for Decentralized Identifiers (DIDs). They store the DID Document, which contains public keys and service endpoints, allowing any party to cryptographically verify an entity's identity without a central authority. This enables self-sovereign identity for credentials, access control, and authentication.

• Key Standard: W3C Decentralized Identifiers (DIDs).
• Example: A university issues a verifiable credential (e.g., a diploma) anchored to a VDR, which a graduate can then present to an employer for instant, fraud-proof verification.

VDRs create immutable, auditable records of a product's journey. Each step—from raw material sourcing to manufacturing and delivery—is logged as a verifiable claim anchored on the registry. This provides end-to-end traceability, combating counterfeiting and ensuring compliance with ethical and sustainability standards.

• Core Mechanism: Each transfer or transformation event is signed by the responsible party and its hash is committed to the VDR.
• Verification: Consumers can scan a QR code to cryptographically verify the entire product history, confirming authenticity and origin.

VDRs are critical for issuing and verifying verifiable credentials and attestations. Issuers (e.g., governments, institutions) create digitally signed credentials whose status (valid/revoked) is anchored on the VDR. Holders can present cryptographic proofs (like ZK-SNARKs or BBS+ signatures) without revealing the underlying data.

• Key Protocols: W3C Verifiable Credentials, AnonCreds.
• Use Case: A user proves they are over 21 by presenting a zero-knowledge proof derived from a driver's license credential anchored in a VDR, without disclosing their birth date or ID number.

VDRs act as a neutral, verifiable state layer for cross-chain communication. They don't hold assets but record cryptographic commitments about the state of connected chains (e.g., block headers, merkle roots). This allows light clients to verify proofs about events on another chain, enabling secure bridges and interoperability protocols.

• Function: Provides a universally agreed-upon source of truth for state proofs.
• Example: A bridge uses a VDR to verify that assets were locked on Chain A before minting a representation on Chain B, with the proof being independently verifiable by anyone.

Organizations use VDRs to create cryptographic audit trails for critical internal data. By periodically publishing data hashes (e.g., of log files, database snapshots, or compliance reports) to a public or permissioned VDR, they create a timestamped, immutable proof of data existence and integrity at a point in time.

• Key Benefit: Provides non-repudiation and simplifies external audits.
• Process: A hash of the quarterly financial report is anchored. Auditors can later verify that the report presented matches the hash committed on the specified date, proving it hasn't been altered.

The core security mechanism where data commitments (hashes) are immutably recorded on a blockchain or distributed ledger. This creates a tamper-evident seal; any alteration to the original data invalidates the cryptographic proof. Common methods include:

• Merkle Proofs: Efficiently prove data inclusion in a large dataset.
• Digital Signatures: Verify the issuer's authenticity and data integrity.
• Blockchain Timestamping: Provides a globally-verifiable proof of existence at a specific time.

A foundational component for user-centric identity in VDRs. A DID is a cryptographically-verifiable identifier controlled by the user, not a central registry. Security considerations include:

• Key Rotation & Revocation: Mechanisms to update or invalidate compromised public keys.
• DID Method Specifications: The security properties depend on the underlying DID method (e.g., did:ethr, did:key).
• Privacy: DIDs can be pairwise (unique per relationship) to prevent correlation across different verifiers.

The primary data object in a VDR, representing a cryptographically-signed attestation. Key security and trust aspects are:

• Selective Disclosure: Using Zero-Knowledge Proofs (ZKPs) to prove claims (e.g., age > 21) without revealing the underlying credential data.
• Status & Revocation: Checking credential validity via revocation registries or status lists without exposing user activity.
• Schema Integrity: Ensuring the credential data structure (credential schema) is itself verifiable and immutable.

A governance and technology stack model that separates concerns to manage trust. The four-layer architecture isolates risks:

1. Governance Layer: Rules, policies, and standards (e.g., who is an accredited issuer?).
2. Utility Layer: The Verifiable Data Registry itself (e.g., a blockchain).
3. Credential Layer: Wallets and agents that exchange Verifiable Credentials.
4. Wallet Layer: User-held devices and software. This separation ensures the VDR's technical security is governed by clear, human-readable legal frameworks.

A VDR must be highly available and resistant to failure. This is achieved through:

• Decentralization: No single point of control or failure. Resilience scales with node distribution.
• Data Redundancy: Replication of the core registry across a peer-to-peer network.
• Censorship Resistance: The inability for any single entity to prevent the writing or reading of valid data proofs.
• Network Consensus: The security of the underlying consensus mechanism (e.g., Proof of Work, Proof of Stake) directly impacts the registry's attack resistance.

VDRs are designed to enhance privacy, contrasting with traditional databases. Critical features include:

• No Personal Data on Ledger: Typically, only cryptographic hashes and DIDs are stored on-chain; sensitive data remains with the user.
• Minimal Correlation: Use of blinded signatures and ZKPs prevents verifiers from linking transactions.
• User Sovereignty: The holder of a credential controls when and with whom to share it, enabling consent-based data exchange.

Decentralized Identifiers (DIDs) are a core component that a Verifiable Data Registry manages. They are globally unique, cryptographically verifiable identifiers controlled by the user, not a central authority. A DID Document, containing public keys and service endpoints, is published to the VDR, enabling secure, self-sovereign identity.

• Key Function: The VDR acts as the root of trust for resolving a DID to its current DID Document.
• Example: The did:ethr:0x... method uses the Ethereum blockchain as its VDR.

Verifiable Credentials are tamper-evident digital claims (like a driver's license) whose authorship can be cryptographically verified. A VDR is crucial for the issuer of a VC, as it provides the public keys needed to verify the credential's signature.

• Role of VDR: The verifier looks up the issuer's DID in the VDR to fetch the public key for signature validation.
• Standard: Defined by the W3C, enabling interoperable digital credentials.

A public, permissionless blockchain is the most common implementation of a Verifiable Data Registry. Its properties of immutability, censorship resistance, and global availability make it ideal for anchoring trust.

• How it works: DID Documents and credential schemas are written as transactions or stored in smart contract state.
• Examples: Ethereum, Bitcoin, and Hedera Hashgraph are used as VDRs for various DID methods.

Self-Sovereign Identity is the architectural paradigm enabled by VDRs, DIDs, and VCs. It gives individuals and organizations control over their own digital identities without relying on centralized registries.

• Core Principle: Users hold and manage their credentials, presenting proofs without revealing raw data.
• VDR's Role: Provides the decentralized, trusted layer for discovering public keys and service endpoints, eliminating central points of failure.

DID Resolution is the technical process of retrieving a DID Document from a Verifiable Data Registry using a DID. A DID Resolver is a software component that performs this lookup according to the rules of the specific DID method.

• Process: Input a DID (e.g., did:web:example.com) → Resolver queries the appropriate VDR → Returns the current, valid DID Document.
• Standardization: Defined by the W3C DID Specification to ensure interoperability.

Trust over IP is a layered architecture framework for decentralized digital trust ecosystems. A Verifiable Data Registry corresponds to the Utility Layer (Layer 1) in the ToIP stack.

• Utility Layer: Provides the global, root-level discovery and verification service for DIDs.
• Higher Layers: Build upon this with credential exchange (Layer 2) and user applications (Layers 3 & 4).