Focusing on the linear decomposition of the S-box layer in Keccak algorithm, a new linear structure construction method was proposed based on the algebraic properties of the S-box. Firstly, to ensure the state data was still linear with that after this linear structure, some constraints about input bits of S-box needed to be fixed. Then, as an application of this technique, some new zero-sum distinguishers of round-reduced Keccak were constructed by combining the idea of meet-in-the-middle attack. The results show that a new 15-round distinguisher of Keccak is found, which extends 1-round forward and 1-round backward. This work is consistent with the best known ones and its complexity is reduced to 2 ²⁵⁷. The new distinguisher, which extends 1-round forward and 2-round backward, has the advantages of more free variables and richer distinging attack combinations.

To achieve efficient software testing under cloud computing environment, a method of generating parallel test cases automatically for functional testing of Web application system was proposed. First, parallel test paths were obtained by conducting depth-first traversal algorithm on scene flow graph; then parallel test scripts were assembled from test scripts referred by the test paths, and parameterized valid test data sets that can traverse target test paths and replace test data in script were generated using Search Based Software Testing (SBST) method. A vast number of automatic distributable parallel test cases were generated by inputting test data into parallel test scripts. Finally, a prototype system of automatic testing in cloud computing environment was built for examination of the method. The experimental results show that the method can generate a large number of valid test cases rapidly for testing in cloud computing environment and improve the efficiency of testing.