Abstract: With the rapid development of technology of cloud computing and cloud storage,more and more businesses and individuals use cloud storage to store data or backup data．When uploading private data to the cloud,the user will lose the absolute control of the data,them data privacy protection becomes a problem that cloud storage has to solve．In order to solve this problem,BSBC (Bit Split Bit Combine),a new data privacy protection method was presented．Before uploading the data,BSBC splits the data according to bit and re-assembled to form a number of data files,then uploads the data to cloud storage servers；when downloading the data,BSBC downloads all the data files,then through the bit combination,revert them to the original file．Experiments show that this method can protect the privacy of users’ data, obtain 17~35times performance improvement compared with traditional encryption．Then assembly language is used is used to optimize the core codes of bit split and bit combination,and instruction scheduling optimization of assembly language to reduce the data conflict and pipeline stalls．Eventually,compared with traditional encryption,BSBC can get 25~35times performance improvement.

Key words: Cloud storage,Data security,Privacy protection,Instruction scheduling optimization