Security unit for use in memory card

DETAILED DESCRIPTION Accordingly, an object of the present invention is to provide a security unit that allows security to be maintained in a small circuit scale.
Another object of the invention is to provide a memory unit that includes a security unit with a small circuit scale.
In an illustrative embodiment of the invention, a security unit includes an encrypting unit for encrypting data in accordance with commands received by the security unit, and a common register for storing both intermediate results and final results of the data encryption.
A switching element operatively coupled to the register selectively outputs the contents of the register.
The switching element is controlled to prevent external access to the intermediate results of the encryption.
The security unit is particularly useful as part of a memory unit that is attachable to a recording/reproductiondevice such as a digital audio recorder/player.
Advantageously, since a common register functions to store both the intermediate calculation result and the final result of the encryption process, it is not necessary to employ a plurality of registers for these functions.
In addition, it is not necessary to utilize multiple encrypting circuits.
Thus, the circuit scale of the security unit can be reduced.