Abstract: ho protect users' privacy,data stored in cloud service provider (CSP) usually needs to be encrypted before being sent to CSP. It brings about a problem that how users search files using keywords over encrypted cloud data. In lots of scenarios, CSP is considered as a potential attacker. According to characteristics of cloud computing, we proposed an efficient privacy-preserving approach to support mufti-keyword search over encrypted data (short for PPMKS)， which is based on binary sort tree for search ( short for I3.S TS). In our PPMKS, authorized users can easily search ci- phertext files using multiple keywords,which can make users enjoy the service of mufti keyword search over encrypted data anywhere and anytime.

Key words: Mufti-keyword scarch,13ShS, CSP, Cloud storage