Security Model for Privacy-Preserving Blockchain-Based Cryptocurrency Systems.

Privacy-preserving blockchain-based cryptocurrency systems have become quite popular as a way to provide confidential payments. These cryptocurrency systems differ in their designs, underlying cryptography, and confidentiality level. Some of these systems provide confidentiality for their users or transactions or both. There has been a thriving interest in constructing different privacy-preserving cryptocurrency systems with improved security and additional features. Nevertheless, many of these available systems lack security models which makes it hard to prove the security properties of these systems. Despite the differences in the privacy notions of existing privacy-preserving cryptocurrency systems, in this paper, we present a first attempt to create a general framework for a privacy-preserving blockchain-based bank PBB . We present the security properties of this system and model the security experiments for each of the properties. Our PBB model can also work for bank-less cryptocurrency systems. Henceforth, we present a brief security analysis for one of the most notable privacy-preserving cryptocurrencies, Monero, using the security model of the PBB system. Our analysis proves that our PBB system can be easily used to formalise the security of other available privacy-preserving cryptocurrencies.