Abstract: Cloud storage security has always been emphasis in cloud security. Zhao et al. proposed a `I'SCS(Trusted Sha- ring over Cloud Storage) scheme, which is incapable of withstanding malicious CSP attacks, according to our analysis. This paper constructed the model of TSCS in terms of its requirements for security. Afterwards, a new TSCS scheme was proposed based on it, Analysis shows the new one relies less on random numbers,and not only retains the security properties of Zhao et al. 's scheme, but also resists tampering of the server, and could be put into application.

Key words: Cloud security, Cloud storage security, Trusted sharing