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One question
Why share a whole record to prove one qualification?
Check disclosed fields, correlation, retention and the proof mechanism.
Suppose a workshop only needs to know whether you completed a particular safety course. A full learning record might also contain a home address, unrelated courses and grades. The recipient should explain the decision it needs to make before asking for the entire record.
A verifiable credential does not automatically hide fields. Selective disclosure means presenting part of a credential while retaining a verifiable proof. Support depends on the issued format, proof mechanism and presentation and verification software. Deleting fields from an ordinarily signed document generally breaks its original integrity check.
Fewer fields can still leave a trail
A presentation that says only “completed training” may carry a stable credential number or identifier that links visits. Timing, network information and retention also matter. Selective disclosure is not anonymity and does not automatically make separate presentations unlinkable.
For example, disclosing an exam-score field still reveals the score. Proving that a required score was reached without showing the number requires suitable proof capabilities. Do not assume every credential supports it; check the product's actual formats and verification flow.
For this example, ask what conclusion is needed, what information is disclosed, who sees it and how long it is kept. Those questions provide a more useful assessment than a blanket “privacy-preserving” label.
Book and sources
This lesson develops the questions in Chapter 4 of 《区块链实战》 with later standards. It is not an excerpt.
Check your understanding
If you disclose only eligibility but reuse one fixed identifier, are presentations unlinkable?
No. A stable identifier and timing can still link interactions. Minimal disclosure and unlinkability are different goals.
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