An analysis of international data encryption algorithm(IDEA) security against differential cryptanalysis

Abstract

The security of international date encryption algorithm (IDEA(16)), a mini IDEA cipher, against differential cryptanalysis is investigated. The results show that IDEA(16) is secure against differential cryptanalysis attack after 5 rounds while IDEA(8) needs 7 rounds for the same level of security. The transition matrix for IDEA(16) and its eigenvalue of second largest magnitude are computed. The storage method for the transition matrix has been optimized to speed up file I/O. The emphasis of the work lies in finding out an effective way of computing the eigenvalue of the matrix. To lower time complexity, three mature algorithms in finding eigenvalues are compared from one another and subspace iteration algorithm is employed to compute the eigenvalue of second largest module, with a precision of 0.001.