In this paper, we propose an encrypted k–anonymization scheme (EAS) to k–anonymize an encrypted database using a domain generalized hierarchy while maintaining the encryption state. Preparation of the domain generalized hierarchy is optional; the proposed EAS can generate domain generalized hierarchies using a Huffman code tree from a database encrypted with searchable encryption. As a result, the user can delegate k–anonymization processing to a third party organization such as the cloud while retaining the confidentiality of the database without preparing a generalized hierarchy. In addition, third-party organizations that are entrusted also have the advantage to eliminate possible of misconduct such as information leakage. In a standard computer experiment, we performed a generalization process, which is the major procedure for our EAS. The generalization process takes around 168 seconds only to achieve k–anonymity with k = 3 on 1,000,000 records consisting of 4 attributes. As a consequence, this high-speed performance means our EAS is applicable to not only batch processing but also real-time processing.

In recent years, Bitcoin, Ethereum and other cryptocurrencies have attracted a great deal of attention from the whole industry including the financial as a new settlement system. Transaction information of these cryptocurrencies is stored in a distribution ledger called Blockchain on the P2P network through processing such as PoW. Meanwhile, since PoW requires a large amount of computer resources, researches on private / consortium type blockchain that do not need PoW. In this paper, we propose a decentralized netting protocol using a consortium type block chain that has the channel function. On a system that implements the proposed protocol, netting settlement can be performed on P2P hiding information of the sender and receiver name of transaction, amount of money, calculation butt of netting, and without setting up a specific central organization such as a central server.