Blockchain Implementation for Digital Transaction Data Security: A Permissioned-Ledger Framework with Cryptographic Integrity and Byzantine Fault-Tolerant Consensus

Abstract

Nevertheless, the integrity of transactional records remains subject to attacks by malicious data tampering, failure of a central node, insider attacks, and transaction repudiation, especially if the records are stored in one centrally controlled database. In this work, we outline the design and development of a permissioned blockchain architecture with integrity, authenticity, and non-repudiation of the recorded digital transaction data. The proposed blockchain framework utilizes SHA-256 cryptographic hash, Merkle-tree commitment scheme over transaction set of each block, ECDSA signature over individual transactions, and PBFT consensus scheme for a pre-defined number of validating institutions. The prototype of the blockchain was developed using Python and analyzed in a four-node network. The experimental results show that any modification made to the committed record is revealed deterministically – a one-bit change causes changes in about half of the 256 bits of the digest and makes all the blocks following this one compromised. Throughput grows linearly depending on block size until a threshold point is reached and further becomes super-linearly growing. Such an experiment demonstrates the tradeoff between the blockchain throughput and end-to-end latency. Security analysis reveals how the developed permissioned blockchain resists to tampering, transaction repudiation, Sybil and replay attacks. Residual risks include possible keys compromise, collusion of validators and the problem of personal data storage according to existing regulations. The results show that a permissioned blockchain may be considered as a reliable layer for ensuring integrity and accountability of the digital transactions provided that the key management and governance is treated as one of the core problems of engineering.