Focused on the problems of no protection for the number of zero elements in original matrix and no verification for the result returned by cloud in outsourcing algorithm of matrix full rank decomposition, a verifiable and secure outsourcing scheme of matrix full rank decomposition was proposed. Firstly, in the phase of encryption, a dense invertible matrix was constructed by using the Sherman-Morrison formula for encryption. Secondly, in the phase of cloud computing, the cloud computing of the full rank decomposition for the encryption matrix was required. And when the results of full rank decomposition for encryption matrix (a column full rank matrix and a row full rank matrix) were obtained, the cloud computing of the left inverse of the column full rank matrix and the right inverse of the row full rank matrix was required respectively. Thirdly, in the phase of verification, the client not only needed to verify whether these two matrices returned by cloud are row-full-rank or column-full-rank respectively, but also needed to verify whether the multiplication of these two matrices is equal to the encryption matrix. Finally, if the verification was passed, the client was able to use the private key to perform the decryption. In the protocol analysis, the proposed scheme is proved to satisfy correctness, security, efficiency, and verifiability. At the same time, when the dimension of the selected original matrix is 512×512, with different densities of non-zero elements in the matrix, the entropy of the encryption matrix calculated by this scheme is identically equal to 18, indicating that the scheme can protect the number of zero elements effectively. Experimental results show the effectiveness of the proposed scheme.

The research on image Information Hiding (IH) algorithm based on error-correcting code is aimed at overcoming poor robustness flaws of spatial domain image information hiding algorithm. The property of correcting random error of the error-correcting code could be used to improve the robustness of spatial domain information hiding algorithm, so that the modifications to the covers by attacker could be effectively resisted. Two different algorithms were proposed: the Least Significant Bit (LSB) information hiding algorithm based on error-correcting code and the gray-bit information hiding algorithm based on error-correction code. By embedding the coding form of secret information in LSB in the first algorithm, relatively high robustness could be achieved in the case of low density noise; while in the second one, by applying the structural characteristics of image pixel gray values, and coding each pixel gray value which had been embedded the secret information in the form of Hamming code, one error could be corrected by each pixel independently. Both theoretical analysis and experimental results show that, under the condition of same density and value of noise, the percentages of secret information recovered of these two algorithms are higher than the basic LSB algorithm, so they are two information hiding algorithms with higher robustness.

Concering that the traditional access control methods fail to support dynamic authorization and file evaluation, and suffer from malicious re-sharing issue, an Access Control Mechanism with Dynamic Authorization and File Evaluation (DAFE-AC) was proposed. DAFE-AC adopted a dynamic authorization mechanism to monitor authorized users in real-time and allowed users to supervise each other. The file evaluation mechanism in DAFE-AC could dynamically update the access threshold of files. Based on the Hash/index database, DAFE-AC can ensure the uniqueness of files in the system. In DAFE-AC, a user' authorization value can dynamically change with behaviors of other users, and users can perform file evaluation to eliminate malicious re-sharing of files.

Coding cryptography is widespread concerned because it has the advantages of resisting quantum algorithm. To protect the anonymous message, a kind of blind signature scheme based on coding was proposed. By Hash technique and blind factor, message owner sent irreversible and blinding message to the signer, signer completed blind signature by using Courtois-Finiasz-Sendrier (CFS) signature scheme and sent it back to the message owner, message owner obtained signature by blind removing operation. Analysis show that the new scheme not only has the basic nature of general blind signature, but also inherit the advantages of CFS signature scheme such as high security and short signature length, in addition, it can effectively resist attacks of quantum algorithm.