Patent ID: 7272856

Claim:
A decryption device comprising: an internal-key storage section adapted to store an internal-key; a content-key storage section adapted to store content-keys; a determination section adapted to determine whether or not a value of the content-key storage section in an initial state and a current value of the content-key storage section are different; and an operation section, the operation section including: a first decrypting section adapted to, when an encrypted content-key is input to the operation section, decrypt the encrypted content-key using the internal-key so as to obtain a content-key and store the content-key in the content-key storage section, and a second decrypting section adapted to, when an encrypted content is input to the operation section and the determination section determines that the value of the content-key storage section in the initial state and the current value of the content-key storage section are different, decrypt the encrypted content using the current value of the content-key storage section as the content-key so as to obtain a first output data and output the first output data to outside of the decryption device, wherein the determination section comprises a register for storing a value of the content-key storage section at the time that said register receives a Power On Reset (POR) signal, and wherein the POR signal is a signal which pulses only once immediately after power-on or immediately after reset, so that the content key storage section is in the initial state immediately after a corresponding power-on or reset of the decryption device.