Abstract. We propose a new general approach to the construction of on-line non-transferable signatures introduced by Liskov and Micali. Our approach is based on an extension of designated verifier proofs which provides interaction simulatability as opposed to transcript simulatability. We then propose a concrete on-line non-transferable scheme which is proved secure in the standard model. Our scheme allows a less restrictive and more practical operation, is more efficient, and meets a stronger notion of security than the previous approach by Liskov and Micali.

Cloud computing dynamically provides high quality cloudbased secure services and applications over the internet. The efficient sharing of secure cloud storage services (ESC) scheme which allows the upper-level user to share the secure cloud storage services with multiple lower-level users. In hierarchical identity-based architecture, the sender needs to encrypt a file only once and store only one copy of the corresponding ciphertext in a cloud. The lower-level user needs to decrypt a file which will increase the computational overhead, because the lower-level user does not perform any partial decipherment. In this paper, we propose a Trapdoor commitment scheme that enables a lower-level user to send a short trapdoor to the cloud service provider before retrieving files. This scheme allows the CSP to participate in the partial decipherment, so as to reduce computational overhead on the users without leaking any information about the plaintext. If a lower-level user wants to retrieve a file with limited bandwidth, CPU and memory, the trapdoor which will largely helps to reduce computational power. Keywords Hierarchical identity-based encryption; secure storage; trapdoor; partial decipherment. 1.