  Electronic Bill (E-Bill) is a rucial negotiable instrument in the form of
data messages, relying on the Electronic Bill System (EB System). Blockchain
technology offers inherent data sharing capabilities, so it is increasingly
being adopted by small and medium-sized enterprises (SMEs) in the supply chain
to build EB systems. However, the blockchain-based E-Bill still face
significant challenges: the E-Bill is difficult to split, like non-fungible
tokens (NFTs), and sensitive information such as amounts always be exposed on
the blockchain. Therefore, to address these issues, we propose a novel data
structure called Reverse-HashTree for Re-storing transactions in blockchain. In
addition, we employ a variant of the Paillier public-key cryptosystem to ensure
transaction validity without decryption, thus preserving privacy. Building upon
these innovations, we designed BillChain, an EB system that enhances supply
chain finance by providing privacy-preserving and splitting-enabled E-Bills on
the blockchain. This work offers a comprehensive and innovative solution to the
challenges faced by E-Bills applied in blockchain in the context of supply
chain finance.
