Patent ID: 7962753
Filing Date: 2011-06-14
Classification: H04L

Abstract:
1. A Secure Hash Algorithm (SHA) operation method comprising: a store step of storing, in first to fifth storages, first to fifth variables for use in a hash operation on a basis of a SHA-1 algorithm; a permutation step of permuting the first to fifth variables stored as first to fifth intermediate values, respectively; a first calculation step of calculating a temporary value of the SHA-1 algorithm by use of input data and the first to fifth intermediate values permuted; a selection step of selecting one of the first to fifth storages which is for use in storing the temporary value calculated; a maintenance step of storing the temporary value in the selected storage, bitwise-rotating one of the variables which is stored in another of the storages to store a resultant value in the other storage, and maintaining the variables stored in remaining ones of the storages without change, said maintenance step being performed successively in a timing in synchronization with clock cycles; and a second calculation step of calculating a hash value of the input data by the use of the variables held in the storages; wherein when at least one of the first to fifth intermediate values is permuted by bitwise rotation, in said first calculation step, the temporary value is calculated by the use of the intermediate values bitwise rotated, and said maintenance step maintaining, while the temporary value calculated by the use of the intermediate values is stored in the selected storage, the variable stored in the other storage without bitwise rotation as well as the variables stored in the remaining storages.