At a higher level, if you’re willing to do business with someone, and you’re providing or accepting fiat, goods, or services, there is a baseline level of trust between parties and an understanding that any breakdowns in trust will be resolved by contract law and courts.
Apple has coincidently released functionality as part of iOS 15 for verifiable health records data. Note the use of digital signature crypto primitives.
> Find out how you can securely request access to someone's verifiable health records and incorporate that data safely into your app. The Health app helps people download, view, and share their health records, including their COVID-19 immunization and test results — and iOS 15 brings support for the Smart Health Card, a verifiable health record that incorporates the FHIR health data standard. We'll show you how your app can go about requesting access to this record and how you can verify the signature of the file using CryptoKit and the issuer's public key.