Almost all P2P crypto-currencies prevent double spending and similar such attacks with a bulky "blockchain" scheme, and the ones which do not typically use some sort of pseudo-centralized solution to manage the transactions. Here I propose a purely P2P crypto-currency scheme with a finite blockchain, dubbed the "mini-blockchain". Each time a new block is solved the oldest block is trimmed from the end of the mini-blockchain so that it always has the same number of blocks. It is argued that the loss of security this trimming process incurs can be solved with a small "proof chain" and the loss of coin ownership data is solved with a database which holds the balance of all non-empty addresses, dubbed the "account tree". The proof chain secures the mini-blockchain and the mini-blockchain secures the account tree. This paper will describe the way in which these three mechanisms can work together to form a system which provides a high level of integrity and security, yet is much slimmer than all other purely P2P currencies. It also offers other potential benefits such as faster transactions and lower fees, quicker network synchronization, support for high levels of traffic, more block space for custom messages, and increased anonymity.
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