For the difference of transmutative Singular Value Decomposition (SVD++) algorithm's rating rule in two stages of model training and prediction, and the same probability of List-wise Matrix Factorization (ListRank-MF) algorithm's Top-1 ranking probability caused by a large number of same rating items, an algorithm of list-wise matrix factorization combining with item popularity was proposed. Firstly, the current item to be rated was removed from the set of items that the user had used in the rating rule. Secondly, the item popularity was used to improve the Top-1 ranking probability. Then the stochastic gradient descent algorithm was used to solve the objective function and make Top- N recommendation. Based on the modified SVD++ rating rule, the proposed algorithm and the SVD++ algorithms whose objective functions are point-wise and list-wise were compared on MovieLens and Netflix datasets. Compared with the list-wise SVD++ algorithm, the value of Normalized Discounted Cumulative Gain (NDCG) of Top- N recommendation accuracy was increased by 5%-8% on MovieLens datasets and about 1% on Netflix datasets. The experimental results show that the proposed algorithm can effectively improve the Top- N recommendation accuracy.

The existing schemes against global wiretapping attacks for network coding have the problems of bringing bandwidth overhead and incuring high computational complexity. In order to reduce the bandwidth overhead and enhance the actual coding efficiency, a novel secure network coding scheme against global wiretapping was proposed. For the network coding with the size of field is q, two permutation sequences of length q were generated by using the key, and the source message was mixed and replaced by using the permutation sequences so as to resist global wiretapping attacks. The source message was only encrypted at the source node and had no change at the intermediate nodes. The proposed scheme has a simple encryption algorithm, low coding complexity and doesn't need pre-coding, so it doesn't bring bandwidth overhead and has high actual coding efficiency. The analysis results show that the proposed scheme can resist not only the ciphertext-only attacks but also the known-plaintext attacks efficiently.