  In this paper, we present the first large-scale and systematic study to
characterize the code reuse practice in the Ethereum smart contract ecosystem.
We first performed a detailed similarity comparison study on a dataset of 10
million contracts we had harvested, and then we further conducted a qualitative
analysis to characterize the diversity of the ecosystem, understand the
correlation between code reuse and vulnerabilities, and detect the plagiarist
DApps. Our analysis revealed that over 96% of the contracts had duplicates,
while a large number of them were similar, which suggests that the ecosystem is
highly homogeneous. Our results also suggested that roughly 9.7% of the similar
contract pairs have exactly the same vulnerabilities, which we assume were
introduced by code clones. In addition, we identified 41 DApps clusters,
involving 73 plagiarized DApps which had caused huge financial loss to the
original creators, accounting for 1/3 of the original market volume.
