Patent ID: 6359986
Filing Date: 2002-03-19
Classification: H04L

Abstract:
An encryption system comprising a key management device, encryption devices of M types, and decryption devices of N types, wherein M and N are both integers that are no less than 2, the encryption system comprising:the key management device being disposed for storing M encryption key sets, N decryption key sets, and N identification numbers, distributing a different one of the M encryption key sets to all encryption devices of a same type out of the M types, distributing a different one of the N decryption key sets to all decryption devices of a same type out of the N types, and distributing a different one of the N identification numbers to all decryption devices of the same type out of the N types, wherein each encryption key set includes N encryption keys, and each decryption key set includes a predetermined number of decryption keys; each encryption device being disposed for encrypting digital data using a scramble key to generate encrypted digital data, encrypting the scramble key using each of N encryption keys included in a distributed encryption key set to generate N encrypted scramble keys, and writing the encrypted digital data and the N encrypted scramble keys into a distribution medium; and each decryption device being disposed for decrypting an encrypted scramble key, which is identified by a distributed identification number, among the N encrypted scramble keys written in the distribution medium, using each of the predetermined number of decryption keys included in a distributed decryption key set, selecting a decryption key that correctly decrypts the encrypted scramble key according to a predetermined criterion, and decrypting the encrypted digital data written in the distribution medium using the scramble key obtained by correctly decrypting the encrypted scramble key to obtain the digital data, and wherein the key management device includes: a first ciphertext read unit disposed for reading an encrypted scramble key from the distribution medium; a decryption key set read unit disposed for reading a decryption key set from the N decryption key sets; a decryption selection unit disposed for decrypting the read encrypted scramble key using each of the predetermined number of decryption keys included in the read decryption key set in order to select a decryption key, among the predetermined number of decryption keys, that correctly decrypts the encrypted scramble key according to the predetermined criterion; a first repeat control unit disposed for controlling the first ciphertext read unit, the decryption key set read unit, and the decryption selection unit in order to respectively repeat an encrypted scramble key reading, a decryption key set reading, and an encrypted scramble key decryption, until the N encrypted scramble keys are read from the distribution medium, wherein N decryption keys are selected as a result of a control by the first repeat control unit; and a key pattern detection unit disposed for detecting an encryption key set, among the M encryption key sets, that matches the selected N decryption keys and identifying an encryption device type, among the M types, specified by the detected encryption key set.