Table 1.

Key features and affordances of blockchain technology

Key principles	Corresponding features	Affordances
Proof	Immutable record of transactions	Tamper-proof evidence of consent, data entry or other processes having occurred; useful for journal submissions, fraud prevention and liability concerns; supply chain management (pre/postmarket surveillance).
	Sequential timestamping	Allows proof that events happened at specific times and in specific order: for instance, tracking protocol versioning and coherence with (re)consent requirements or outcome analysis.
Differential publicity	Transparency of transactions and records	Deviations from protocol, consent, endpoints, statistical plan, and so on auditable; control over level of data visibility.
	Pseudonymity via public cryptographic identifiers	Degree of privacy can be set according to need or preference; pseudonymous identification and contact possible: prosent.
Distribution	Decentralised data access management	Accessibility of the data: control of data requests, ownership and access by patients and stakeholders are managed on the blockchain. Access of the data: data are stored off chain. Security and integrity through no database single point of failure.
	Blockchain data structure	Compatibility with distributed computing: data analytics, machine learning (federated learning, distributed secure computing, and so on).
	Consensus mechanism	Depending on the choice of the blockchain, all users or relevant stakeholders can participate in the governance and development of the blockchain, essentially on two aspects: consensus mechanism (validation nodes, proof modalities), consensus about the source code of the technology and its update.
Automation	Smart contracts	Automation of key processes (eg, claims, study recruitment, some types of data analysis, and many others), reduction of errors and fraud, integration with connected devices.