PRAMAAN: A Zero-Trust, Blockchain-Anchored Architecture for Tamper-Evident Validation of Confidential Reports

Abstract

Sensitive documents, such as financial audits, compliance reports, security assessments, and digital evidence, must be protected against unauthorized changes while ensuring that approvals and access permissions can be verified. Centralized document-management systems are efficient but depend on a trusted authority, whereas storing complete documents on a distributed ledger can create confidentiality and scalability issues. This paper presents PRAMAAN, a platform that addresses these challenges by storing encrypted documents off-chain and recording their cryptographic proofs on a ledger. Reports are encrypted using AES-256-GCM, and their SHA-256 hashes are recorded in an append-only, hash-chained ledger whenever a new version is created. Ed25519 digital signatures link approvals to the document version, signer, and role. A zero-trust access-control mechanism evaluates each sensitive request against current permissions and time-limited access grants. Document integrity is verified by recalculating the hash and comparing it with the ledger record, helping detect unauthorized modifications. The platform supports a single-node hash-chain ledger and provides a Hyperledger Fabric adapter for alternative deployment. Experimental results show an Ed25519 verification time of 0.078 ms, an end-to-end verification time of 0.60 ms for a 1 MB document, and an average ledger-operation time of 0.0024 ms per event. Recording only a 32-byte hash reduces ledger storage requirements by more than 32,000 times compared with storing a 1 MB document on-chain. A 48-case automated test suite evaluates security-critical functions, including signature binding and hash-chain tamper detection.