METHOD AND DEVICE FOR GENERATING COMMON KEY AND CIPHER COMMUNICATION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a method and a device for common key generation and a cipher communication method which can make a common key generated by each entity variable in length and are adaptive to a key common ownership system having the arbitrary number of bits. SOLUTION: In generating a common key which is used to cipher a plaintext M into a ciphertext C and decipher a ciphertext C into a plaintext M, a component selector 11 (21) extracts components which are included in respective secret leys of one entity a (b) corresponding to the other entity b (a) a communication partner and a common key generator 12 (22) generates a common key Kab (Kba) by shifting and putting together the extracted components.