Confidential and auditable payments

Abstract

In this paper, we construct the Confidential and Auditable Payments (CAP) scheme. We keep the transaction confidential by writing ciphertexts of transactions in a ledger. We realize the soundness of the CAP scheme by the soundness of the zero-knowledge proof. A court or an authority controls a unique secret key of the ciphertexts written in the ledger. They can enforce confidential transactions open with the secret key according to the legal procedure. There are many works for protecting the transaction’s privacy strictly. However, these works do not have a forcibly auditable function, to the best of our knowledge. The proposed scheme is both confidential and auditable. It eliminates concerns about money laundering caused by excessively confidential transactions and contributes to the sound use of blockchain.