  Bitcoin-NG is an extensible blockchain protocol based on the same trust model
as Bitcoin. It divides each epoch into one Key-Block and multiple Micro-Blocks,
effectively improving transaction processing capacity. Bitcoin-NG adopts a
special incentive mechanism (i.e., the transaction fees in each epoch are split
to the current and next leader) to maintain its security. However, there are
some limitations to the existing incentive analysis of Bitcoin-NG in recent
works. First, the incentive division method of Bitcoin-NG only includes some
specific mining attack strategies of adversary, while ignoring more stubborn
attack strategies. Second, once adversaries find a whale transaction, they will
deviate from honest mining strategy to obtain extra reward. In this paper, we
are committed to solving these two limitations. First, we propose a novel
mining strategy named Greedy-Mine attack. Then, we formulate a Markov Decision
Process (MDP) model to analyze the competition of honest miners and
adversaries. Furthermore, we analysis the extra reward of adversaries and
summarize the mining power proportion range required for malicious adversaries
to launch Greedy-Mine to obtain extra returns. Finally, we make a
backward-compatibility progressive modification to Bitcoin-NG protocol that
would raise the threshold of propagation factor from 0 to 1. Meanwhile, we get
the winning condition of adversaries when adopting Greedy-Mine, compared with
honest mining. Simulation and experimental results indicate that Bitcoin-NG is
not incentive compatible, which is vulnerable to Greedy-Mine attack.
