Analysis of Data Encryption Mechanisms for Searchable Encryption

Recently, the need for outsourcing sensitive data has grown due to the wide spreading of cost-effective and flexible cloud service. However, there is a fundamental concern in using such service since users have to trust external servers. Therefore, searchable encryption can be a very valuable tool to meet the security requirements of data outsourcing. However, most of work on searchable encryption focus only on privacy preserving search function and relatively lacks research on encryption mechanism used to actually encrypt data. Without a suitable latter mechanism, searchable encryption cannot be deployed in real world cloud services. In this paper, we analyze previously used and possible data encryption mechanisms for multi-user searchable encryption system and discuss their pros and cons. Our results show that readily available tools such as broadcast encryption, attribute-based encryption, and proxy re-encryption do not provide suitable solutions. The main problem with existing tools is that they may require separate fully trusted servers and the difficulty in preventing collusion attacks between outsiders and semi-trusted servers.