Blockchain notarizes live changes in shared digital documents
Fluid Notarization: Verifiable Evolution of Concurrently Edited Structured Documents
Distributed, Parallel, and Cluster ComputingCryptography and Security
Summary
Traditional blockchain methods record each version of a document separately, which is inefficient for documents edited by many people at once. The authors propose a new approach called Fluid Notarization that records the history of changes, not just snapshots. This makes it easier to verify when changes were made and ensures all edits merge correctly without confusion. They tested this idea using electronic health records to show it works in real situations.
What this means in practice
- •For healthcare it teams: Enable seamless, verifiable collaboration on patient records without creating bulky document versions for each edit.
- •For legal document managers: Offer auditable proof of when specific edits were made to contracts jointly edited by multiple parties.
Authors
Amos Brocco, Giuliano Gremlich, Roberto Guidi
Abstract
Traditional blockchain-based document notarization follows a snapshot-oriented model in which each document revision is represented as an independent state anchored on-chain through a cryptographic reference. While effective for immutable artifacts, this approach becomes inadequate when documents evolve through collaborative editing. Concurrent modifications create divergent document versions that must be reconciled outside the notarization layer, while even minor changes require generating and distributing new document snapshots. Conversely, collaborative replication frameworks such as CRDTs provide deterministic reconciliation of concurrent updates, but do not inherently provide independently verifiable evidence of when contributions were published. This paper introduces Fluid Notarization, a notarization paradigm in which document evolution itself becomes the object of notarization. Rather than certifying isolated states, Fluid Notarization certifies a graph of causally related evolution artifacts generated by a JSON-native delta-CRDT. The proposed model builds upon Melda, which represents document changes as compact, content-addressed deltas linked through causal dependencies. Blockchain notarization is reduced to recording identifiers of these evolution artifacts, while synchronization, reconstruction, and conflict resolution remain entirely off-chain. The resulting architecture combines two complementary guarantees: deterministic convergence provided by the CRDT and independently auditable proof-of-existence, provenance, and publication evidence provided by the blockchain. A prototype implementation and validation scenario based on collaboratively edited electronic health records demonstrate the feasibility of the approach and highlight the advantages of notarizing document evolution rather than successive document snapshots.