To solve the problem that some area deforms too large and large volume of redundant data in the process of panoramic video mapping, a Double-Ring mapping Projection (DRP) algorithm was proposed. Firstly, according to the geometric characteristics of spherical video and the visual characteristics of Human Visual System (HVS), the spherical video was divided into 14 equal-sized regions by two mutually orthogonal ring areas regions. Then, according to the space domain sampling theorem, the 14 regions corresponding to the spherical video content were mapped to 14 rectangular videos with the same size by Lanczos interpolation method. Finally, according to the characteristics of the latest video coding standard, the 14 rectangular videos were rearranged to get a compact panoramic video in keeping with coding standards. The experimental results show that the DRP algorithm achieve a higher compression efficiency compared with the EquiRectangular mapping Projection (ERP) algorithm, OctaHedral mapping Projection (OHP) algorithm and IcoSahedral mapping Projection (ISP) algorithm. Specifically, compared with the most popular ERP algorithm, the proposed method reduces the bit rate by 8.61% which obviously improves the coding efficiency.

Since there are more and more security issues in cloud storage, this paper designed a new secure and distributed cloud storage model based on the threshold Attribute-Based Encryption (ABE). Three phases in the model included: the encryption phase, the data storage phase and the decryption phase, and all messages in these phases were distributed through the whole process. It not only enhanced the security of the storage data by using the ABE but also supported the threshold decryption and allowed to add or remove the arbitrary attribute authorities, with the use of the multi-attribute authorities method in the model. In the data storage phase, this paper used the distributed erasure code to improve the robustness of our model and this model could resist against collusion attack. It can be applied in some special cloud situations and provides secure cloud storage service for users.

To improve the computational efficiency in the threshold signature scheme, the authors proposed a new threshold signature scheme based on bilinear pairing via combining Gennaro's (GENNARO R, JAREAKI S, KRAWCZYK H, et al. Secure distributed key generation for discrete-log based cryptosystem. Journal of Cryptology, 2007, 20(1): 51-83) distributed secret key generation solution and Gu's (GU K, JIA W J, JIANG C L. Efficient and secure identity-based signature scheme. Journal of Software, 2011, 22(6): 1350-1360) signature scheme in the standard model. There was no trusted dealer for secret key share distribution and each party could verify the validity of some important information, which guaranteed the proposed scheme can avoid the malicious private key generator attack and public key share replacing attack. The comparison results with two previous threshold signature schemes show that the proposed scheme needs less pairing computation and raises the computational efficiency.