This chapter will introduce the zkToken protocol. In terms of overall architecture, zkToken utilizes a variant of Pedersen commitments, with its main scheme drawing inspiration from PGC, albeit with slight differences in detail.

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Twin-token protocol

zkToken adopts twin-token protocol, which ensures the composability of the protocol with popular public chain projects while supporting flexible capital flow between plaintext and ciphertext accounts. Existing privacy protocols mostly involve modifications to the underlying blockchain, which can ensure privacy but often sacrifice composability with other protocols. Additionally, many privacy protocols are relatively simplistic, treating all user data as private without distinguishing between plaintext and ciphertext, let alone enabling interaction between them.

DCPA proposes a twin-token protocol to address these two issues effectively. Users register an existing ERC20 token, such as USDT, through the twin-token protocol. This protocol then deploys a corresponding privacy contract for the ERC20, ensuring that the data in this contract is ciphertext and does not affect the original ERC20 contract.

In practice, if users opt for plaintext interaction, they directly interact with the original ERC20. For ciphertext interaction, they engage with the privacy ERC20. In cases requiring interaction between plaintext and ciphertext, such as transactions involving both types, the twin-token routing contract facilitates the transfer between the two contracts.