| With the development of cloud services,more and more users use cloud storage services to outsource their data to cloud servers.In order to prevent data leakage,users can store data in the cloud server in ciphertext.However,cloud data stored in ciphertext still faces security risks such as disclosure and abuse.This is because the data is stored on the cloud server and the data user,so the data owner cannot physically delete the data.Once the key for encrypting the data is leaked,the data will also be leaked.To this end,researchers have proposed a assured deletion method to ensure that cloud data is invalid and unrecoverable after deletion.However,most of the existing assured deletion schemes are designed and implemented on computers and smartphones,which have abundant resources,and cannot be directly applied to embedded devices with limited resources,and lack of verification of the platform credibility of data users,making the security assumption of the scheme ideal.Therefore,this paper uses JavaCard as a specific carrier to study the problem of assured deletion of cloud data in embedded scenarios.The basic idea is to use remote attestation technology to verify the platform credibility of data users.If it is credible,the data owner will sends the key and key usage conditions required to access the data to the data user.When the key usage conditions are met,the data user can normally access the data;when the key usage conditions are not met,the key will be safely deleted,so that the data can no longer be accessed.Specifically,the work of this paper includes:(1)Self-measurement remote attestation method under the JavaCard platform.In order to verify the credibility of the data user platform,this paper proposes a method of implementing remote attestation protocol in a self-measured manner with JavaCard as the root of trust.This method will trigger the JavaCard to perform integrity measurement operations on the local platform according to a time point in a random schedule,so that the data user will also perform multiple measurement operations on itself when the data user does not receive a remote attestation request,so as to achieve a higher confidence proves to the data owner that the platform is credible.Then,when receiving a remote attestation request,the data user will return multiple measurement results to the data owner at one time,thereby effectively reducing the number of response times and saving communication overhead.(2)Assured deletion method supporting key use time and times under JavaCard platform.This method supports two key usage conditions of time and number of times,and for these two usage conditions,data users can use the storage feature provided by JavaCard to safely store the key and usage conditions locally,so that data users do not need to request keys again every time the data is used,thus saving communication overhead.When the conditions for using the key are met,JavaCard uses the key to decrypt the data and returns the plaintext data to the application.When the key usage conditions are not met,JavaCard will securely delete the key and generate publicly verifiable key deletion evidence.Experiments and comparative analysis show that the performance overhead of this scheme is reasonable and suitable for embedded devices. |
