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BZIP: A Compact Data Memory System for UTXO-based Blockchains

Unspent Transaction Output (UTXO) set is the foundational model used in many blockchain systems to represent assets. The benefits of UTXO representation include parallel processing, privacy, etc. However, the increasing size of UTXO set is degrading the access performance and severely brings down the validation speed of blockchain further, especially in resource-constrained scenerios, such as IoT. In this paper, we present a memory-economical storage system for UTXO-based blockchain. Based on the inherent properties of UTXO set, we propose two lossless compression techniques to reduce the memory space occupied by UTXO set. Besides, the database related operations are adopted to make the proposed mechanism easily applied in current blockchain system. Taking Bitcoin as the object of study, our mechanism can deliver 2.9-4.5x memory reduction and orders of magnitude validation speed improvement in resource-constrained situations. This compact system will improve validation performance and extend applied scope of blockchains.