RingCT 3.0 for Blockchain Confidential Transaction: Shorter Size and Stronger Security

Abstract

In this paper, we propose the most efficient blockchain ring confidential transaction protocol (RingCT3.0) for protecting the privacy of the sender’s identity, the recipient’s identity and the confidentiality of the transaction amount. For a typical 2-input transaction with a ring size of 1024, the ring signature size of our RingCT3.0 protocol is 98% less than the ring signature size of the original RingCT1.0 protocol used in Monero. Taking the advantage of our compact RingCT3.0 transcript size, privacy-preserving cryptocurrencies can enjoy a much lower transaction fee which will have a significant impact on the crypto-economy. In addition to the significant improvement in terms of efficiency, our scheme is proven secure in a stronger security model. We remove the trusted setup assumption used in RingCT2.0. Our scheme is anonymous against non-signing users who are included in the ring, while we show that the RingCT1.0 is not secure in this improved model. Our implementation result shows that our protocol outperforms existing solutions, in terms of efficiency and security.