  Ethereum has become a popular blockchain with smart contracts for investors
nowadays. Due to the decentralization and anonymity of Ethereum, Ponzi schemes
have been easily deployed and caused significant losses to investors. However,
there are still no explainable and effective methods to help investors easily
identify Ponzi schemes and validate whether a smart contract is actually a
Ponzi scheme. To fill the research gap, we propose PonziLens, a novel
visualization approach to help investors achieve early identification of Ponzi
schemes by investigating the operation codes of smart contracts. Specifically,
we conduct symbolic execution of opcode and extract the control flow for
investing and rewarding with critical opcode instructions. Then, an intuitive
directed-graph based visualization is proposed to display the investing and
rewarding flows and the crucial execution paths, enabling easy identification
of Ponzi schemes on Ethereum. Two usage scenarios involving both Ponzi and
non-Ponzi schemes demonstrate the effectiveness of PonziLens.
