Watermarking method for smart contract

Abstract

A watermarking method for smart contract according to an embodiment of the present disclosure comprises compiling a source code of a smart contract to create a contract creation bytecode and a runtime bytecode; generating a control flow graph including a plurality of byte regions based on the runtime bytecode; setting opcode groups by grouping consecutive opcodes in an opcode list in the plurality of byte regions of the generated control flow graph so that a sum of gas costs for the consecutive opcodes is greater than or equal to a preset gas cost value; extracting a watermarkable byte region based on the set opcode groups; determining watermarking bytes, in which a watermark is to be embed in the watermarkable byte region, to embed the watermark and storing location information of the determined watermarking bytes; hashing fingerprint information including information on the watermark and the location information of the watermarking bytes to create a fingerprint; and embedding the created fingerprint in the contract creation bytecode to deploy the smart contract. Hence, the watermark can be embedded without an additional executable code and a gas fee in a smart contract program.