Abstract: The cloud & client computing can take full aggregation of network server-side and edge node computing resources of Internet to gain greater benefits. However, deploying tasks to terminal nodes would bring the corresponding security risks at the same time. The behaviors of terminal nodes belonging to different users are clearly not reliable,which means the computing security is difficult to guarantee. One of these security risks is that a terminal node working as the task executor may tamper with the program or data of the task, and return the fake result, or pry into the code and data with privacy requirement. hhis paper presented a new code protection mechanism based on encryption function with verification code meeting integrity and privacy both,which makes it possible to effectively verify the correctness of returned results and to guarantee the code not be spied. In order to improve the success rate of task implementation further and reduce job cycle time, tasks ought to be distributed to those nodes with good reputations and high success rate of task implementation to execute. This paper proposed the credibility evaluation of node,described the work procedure of the code protection mechanism and gave the analysis and verification of the security performance of the system in detail.

Key words: Cloud computing, Information security, Code protection, Credibility evaluation