AbstractThis article proposes a simple, efficient, and easy‐to‐use mechanism to add privacy and fine‐grained access control features to a traditional Blockchain. It uses standard cryptographic algorithms and techniques, along with a novel key derivation algorithm and a fuzzy extractor component (that derives a cryptographic key from a biometric), to make access control functionality very simple for nonexpert users. Such a Blockchain would be suitable for the storage of participant data postings in long‐term–isolated environments.