  In 2008, Satoshi Nakamoto proposed an electronic cash system (bitcoin) that
is completely realized by peer-to-peer technology. The core value of this
scheme is that it proposes a solution based on Proof-of Work, so that the cash
system can run in a peer-to-peer environment and be able to prevent
double-spend attacks. Bitcoin has been developed for ten years, and since then
countless digital currencies have been created. But the discussion of
double-spend attacks seems to still concentrate on 51% Attacks. In fact, our
research has found that there are many other way to achieve double-spend
attacks. In this paper, by introducing a number of double-spend attack
vulnerabilities that we have found in EOS, NEO and other large blockchain
platforms, we summarized various reasons for causing double-spend attacks, and
propose an efficient mitigation measure against them.
