Biblio

This paper proposes a lightweight digital signing scheme for supporting document signing on mobile devices connected to cloud computing. We employ elliptic curve (ECC) digital signature algorithm (ECDSA) for key pair generation done at mobile device and introduce outsourced proxy (OSP) to decrypt the encrypted file and compute hash value of the files stored in the cloud system. In our model, a mobile client invokes fixed-sized message digests to be signed with a private key stored in the device and produces the digital signature. Then, the signature is returned to the proxy for embedding it onto the original file. To this end, the trust between proxy and mobile devices is guaranteed by PKI technique. Based on the lightweight property of ECC and the modular design of our OSP, our scheme delivers the practical solution that allows mobile users to create their own digital signatures onto documents in a secure and efficient way. We also present the implementation details including system development and experimental evaluation to demonstrate the efficiency of our proposed system.

In this paper, we propose an access control model featured with the efficient key update function in data outsourcing environment. Our access control is based on the combination of Ciphertext Policy - Attribute-based Encryption (CP-ABE) and Role-based Access Control (RBAC). The proposed scheme aims to improve the attribute and key update management of the original CP-ABE. In our scheme, a user's key is incorporated into the attribute certificate (AC) which will be used to decrypt the ciphertext encrypted with CP-ABE policy. If there is any change (update or revoke) of the attributes appearing in the key, the key in the AC will be updated upon the access request. This significantly reduces the overheads in updating and distributing keys of all users simultaneously compared to the existing CP-ABE based schemes. Finally, we conduct the experiment to evaluate the performance of our proposed scheme to show the efficiency of our proposed scheme.