Two Improved Algorithms Based on Character Encryption and Decryption

To improve the weakness that the same plaintext strings have the same ciphertext strings in character encryption and decryption scheme based on a shift register, this paper presents an improved algorithm of character encryption and decryption based on multi-shift registers disturbance mode. This algorithm can compensate the defect, enlarge the ciphertext space, and improve the crack difficulty of the ciphertext. To change the initial state of a shift register at any time, a new algorithm of character encryption and decryption based on a chaotic sequence is proposed. The algorithm has high security, and can also solve the problem that the same plaintext strings have the same ciphertext strings without increasing the number of shift register.