Clear DefinitionsSelective Disclosure
3 min read
Pronunciation
[si-lek-tiv dis-kloh-zher]
Analogy
Think of selective disclosure like having a highly advanced digital ID card that you can customize for every interaction. If a bouncer at a club only needs to know if you're over 21, instead of showing your entire driver's license (with your full name, address, exact birthdate, etc.), your digital ID allows you to generate a temporary, verifiable proof that *only* states 'Age: Over 21 - Verified ✅'. The bouncer sees just that one piece of information, and nothing else from your ID is revealed. You selectively disclosed only what was necessary.
Definition
In the realm of digital identity, privacy-enhancing technologies (PETs), and data management, selective disclosure is the capability for an individual (the 'prover' or 'holder') to reveal only specific, chosen pieces of information (attributes) from a larger set of their credentials or personal data to another party (the 'verifier'), without exposing any other unrelated or unnecessary information. This empowers users to prove specific facts about themselves while maintaining maximum privacy over the rest of their data.
Key Points Intro
Selective disclosure is a fundamental principle of modern digital identity systems, empowering users with granular control over their personal data by allowing them to share only the minimal necessary information required for any given transaction or interaction.
Key Points
Data Minimization in Practice: Users reveal only the absolutely necessary attributes or claims, rather than entire documents or datasets.
Enhances User Privacy: Significantly protects user privacy by limiting the exposure of sensitive personal information to third parties.
Granular Control & Consent: Enables individuals to have fine-grained control over precisely what information is shared, with whom, and for what purpose.
Key Enabler for SSI & VCs: Often implemented using technologies like Zero-Knowledge Proofs (ZKPs) in conjunction with Verifiable Credentials (VCs) within Self-Sovereign Identity (SSI) frameworks.
Example
A university student needs to prove to an online bookstore that they are an enrolled student to get a discount, but the bookstore doesn't need to know their student ID number or specific courses. Using an SSI wallet containing their student Verifiable Credential (issued by the university), the student can generate a Zero-Knowledge Proof. This proof selectively discloses only the claim 'Is currently enrolled: True' and 'Institution: University X' from their credential, without revealing their name, student ID, date of birth, or other details present in the full credential.
Technical Deep Dive
Selective disclosure is achieved through various cryptographic techniques and data models:
1. **Verifiable Credentials (VCs)**: The W3C VC data model allows credentials to contain multiple claims (attributes). Holders can then create Verifiable Presentations (VPs) that include only a subset of these claims from one or more VCs.
2. **Zero-Knowledge Proofs (ZKPs)**: ZKPs are a powerful cryptographic tool enabling a prover to convince a verifier that a statement about some data is true, without revealing the data itself. For selective disclosure, ZKPs can prove that a certain attribute within a credential meets a specific condition (e.g., `age >= 18`, `country_of_residence == "DE"`) without revealing the actual value of the attribute or any other information from the credential. Common ZKP systems used include zk-SNARKs and zk-STARKs.
3. **Advanced Signature Schemes**: Cryptographic signature schemes like BBS+ signatures allow a signer (issuer) to sign a set of attributes, and then the holder can derive a new signature that proves possession of the original signature while only revealing a chosen subset of those attributes.
4. **Predicate Proofs**: These allow proving that certain conditions (predicates) over hidden attributes are met. For example, proving that age is within a certain range without revealing the exact age.
Security Warning
The security and reliability of selective disclosure systems depend heavily on the strength of the underlying cryptographic primitives, the secure implementation of the protocols, and the integrity of the credential issuers. If the issuance process is compromised, even selectively disclosed information might be based on fraudulent or inaccurate credentials. Verifiers also need to trust the cryptographic mechanisms and ensure they are correctly validating the proofs. Furthermore, even with selective disclosure, metadata (e.g., frequency of interaction) could potentially leak information if not carefully managed.
Caveat
The widespread adoption and usability of advanced selective disclosure technologies require ongoing efforts in standardization (e.g., by W3C, DIF), development of user-friendly wallet applications, and acceptance by verifiers. The complexity of the underlying cryptography can be a barrier to broad understanding and flawless implementation. Ensuring that only the intended information is disclosed and that no unintended data (including through side channels or correlations) is inadvertently leaked requires meticulous protocol design and rigorous security analysis.
Selective Disclosure - Related Articles
No related articles for this term.