CRYPTOGRAPHIC SYSTEM, ENCRYPTION DEVICE, DECRYPTION DECIDE, ENCRYPTION METHOD, DECRYPTION METHOD AND PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide a key distribution technology capable of improving a degree of freedom relating to decryption of a plurality of sections that constitute a content, and also reducing the number of keys.SOLUTION: An encryption device 101 generates cryptographic keys for encrypting sections by inputting an element key belonging to a first hash chain and an element key belonging to a second hash chain, and the sections are encrypted by different cryptographic keys and transmitted. The encryption device 101 further transmits an element key belonging to a first hash chain and an element key belonging to a second hash chain. The element keys are initial keys to be required for decrypting sections that are allowed to be decrypted by a decryption device 103. The decryption device 103 generates cryptographic keys for decrypting sections that are allowed to be decrypted, by applying hash arithmetic operations, times corresponding to positions of the sections, to the received element key belonging to the first hash chain and the received element key belonging to the second hash chain, and decrypts the sections using the generated cryptographic keys.SELECTED DRAWING: Figure 1