Anonymity on blockchain based e-cash protocols—A survey

The transactions in blockchain framework, based cryptocurrencies are publicly available, thereby accessible to all users by design. However, the anonymity of blockchain transactions is necessary for acceptance of such frameworks. There is a need to preserve the privacy of the identities of the blockchain members and the transaction. The main challenge is that anonymity-provisioning mechanism must allow verification by other members for updating the blockchain. The pseudonymous attribute of most of the blockchain-based e-cash protocols is not sufficient for users to attain identity privacy and transaction privacy. This paper provides a comprehensive study of the threats and attacks that aim to deanonymize the e-cash protocols. We present a detailed survey of methods and protocols required for anonymity-provisioning of blockchain-based e-cash transactions. We discussed their features and limitations. We redefined anonymity on the blockchain and categorized the anonymity-provisioning methods and protocols with their outcomes. We provide guidelines for selecting an approach to design an anonymity-provisioning blockchain-based e-cash system. Furthermore, we provide directions for future research in anonymity-provisioning on blockchain-based e-cash protocols.