Criterion of Blockchain Vulnerability to Majority Attack Based on Hashing Power Distribution Assessment

A blockchain distributed ledger is an actively developed technology that goes beyond its original cryptocurrency application and integrates to IoT, smart manufacturing, smart cities, logistics and more. Therefore, the blockchain security is of the current interest. The article considers a blockchain security issue caused by imbalanced hashing power distribution between nodes: the majority attack. The majority attack (the 51% attack) is a technique which intends to fork the blockchain in order to cancel confirmed transactions and violate data integrity. Despite the attack cost, it has become frequent in current blockchains. The existing security mechanisms against the majority attack have significant weaknesses and limitations. This paper proposes a novel criterion of the blockchain vulnerability to the majority attack. The criterion allows to detect vulnerable states of the distributed ledger based on hashing power distribution assessment. The blockchain hashing power time series are constructed and analyzed in order to evaluate the portion of total hashing power that is controlled by attacker. This estimate is used as a foundation of the proposed criterion. The criterion may be used to in conjunction with other security mechanisms to enhance protection of distributed ledgers in vulnerable states.