The Role of Status Lists in Revocation Management

Revocation and suspension of credentials are fundamental to decentralized identity systems. Without an efficient way to check if a credential is still valid, the trust in verifiable credentials (VCs) is compromised. Status Lists provide a scalable and privacy-preserving solution for managing credential revocation. This post breaks down how they work, their challenges, and how Vidos is improving their use.

What Are Status Lists?

Status Lists are a mechanism for tracking the validity of verifiable credentials using bitstrings. Each credential corresponds to a specific index within the bitstring:

• A 0 means the credential is valid.
• A 1 means the credential is revoked or suspended.

Because bitstrings are compact and efficient, they allow issuers to maintain revocation lists without bloating the system with unnecessary data. This makes them a powerful alternative to traditional revocation lists or certificate revocation lists (CRLs), which can become impractically large over time.

Key Attributes of Status Lists

1. Compact and Scalable: Since each credential is mapped to a bit, the overall storage requirement remains small, even for large datasets.
2. Verifiable: The list is cryptographically signed by the issuer, allowing verifiers to trust its integrity.
3. Privacy-Preserving: Only the credential’s status is revealed, not any additional personal data about the holder.
4. Efficient Updates: The issuer can update the list periodically or upon credential revocation, ensuring that the latest status is always accessible.

How Status Lists Are Used in Verifiable Credentials

When a verifier checks a credential, they retrieve the associated Status List and look up the bit at the designated index. If the bit is 0, the credential is still valid. If it is 1, the credential has been revoked or suspended. This approach avoids the need for direct interaction with the issuer each time verification occurs, making the process more efficient and scalable.

Challenges in Status List Usage

While Status Lists provide a structured approach to revocation, they come with some challenges:

1. High Processing Overhead: Large-scale updates and frequent verifications can place a strain on decentralized networks.
2. Delayed Updates: In systems where updates occur periodically rather than in real time, revoked credentials might still appear valid for a short period.
3. Issuer Dependency: If an issuer stops maintaining the Status List, all credentials associated with it lose their revocation tracking, potentially weakening trust in the system.

The Future of Status Lists in Decentralized Identity

As verifiable credentials gain adoption, the need for robust revocation mechanisms will continue to grow. Status Lists provide an efficient, scalable solution, but they are not without their limitations. By addressing privacy concerns, improving update efficiency, and ensuring widespread adoption, we can make them more reliable and practical for real-world use.

Vidos is committed to enhancing the usability and security of decentralized identity solutions, and Status Lists are a critical component of that mission. We welcome feedback from the community to refine and improve these mechanisms further.

For those interested in the technical details, check out the W3C VC Bitstring Status List.