Simple and scalable blockchain with privacy

The three primary requirements in privacy coin are sender anonymity, receiver anonymity, and transaction amount obscurity. In the process of achieving these three requirements, it can result in some side-effects. Some of the side-effects include large blockchain sizes, unpruneable blockchain, unverifiable total coin mintage, and complicated protocol. In this paper, we propose a coin privacy solution that fulfills these three requirements without side-effects. Compared to other solutions, our solution has a bigger anonymity set, easier to understand, and comes with prunable blockchain. However, transactions involving fractionation amount are rounded up to the nearest available denomination. This rounding up is acceptable because it is a similar problem with cash that been used for centuries. Our protocol is an extension of bitcoin P2PKH and CoinJoin features. The CoinJoin is secured with a CoinJoinID, which cryptographical hard to reproduce. We also have proven the security of the pruning process. Other related issues are also described in this paper.