Patent ID: 8000476

Claim:
A method of enciphering data comprising the steps of: subjecting digital information data to enciphering process by an enciphering apparatus using initial common key data (DKI) for a predetermined time and thereafter using common key data (DEY) for producing enciphered information data, subjecting the common key data (DEY) to enciphering process using open key data (DOY) for producing enciphered key data (DXY), and sending a signal including both the enciphered information data and the enciphered key data (DXY); wherein in a deciphering process while the enciphered key data (DXY) is being deciphered, the initial common key data (DKI), which are previously set, are used to decipher the enciphered information data, and after the predetermined time from the start of the deciphering process, once the enciphered key data (DXY) is deciphered to produce the common key data (DEY), the common key data (DEY) are used to decipher the enciphered information data and wherein the digital information data is a high definition (HD) digital signal.