Analysis of Proof-of-Work-Based Blockchains Under an Adaptive Double-Spend Attack
Gholamreza Ramezan, Cyril Leung
Abstract
In this article, we study the performance of blockchains by analyzing the common prefix depth, chain quality coefficient, and chain growth speed coefficient. These three parameters characterize the liveness and consistency of transactions which are important for the proper operation of the blockchain. We examine how these three parameters are affected under an adaptive double-spend attack (ADSA). To maintain the performance of a blockchain against ADSA, the user nodes can use a larger number, z, of confirmation blocks for validating a transaction. A comparison of the values of z needed to achieve a given target probability of successful attack is provided for ADSA and the traditional double-spend attack with different system models. The results indicate that a larger value of z is required under ADSA. A more realistic reward model for attackers is also introduced. It is found that the expected reward of an attacker decreases rapidly to zero as z is increased.