Semiconductor memory device including a flag for selectively controlling erasing and writing of confidential information area

摘要

A semiconductor memory device includes a memory which comprises a confidential information area storing confidential information and a flag. A controller reads the flag from the memory when instructed to erase or write data in the confidential information area, determines whether the flag is set, erases or writes data in the confidential information area when the flag is clear, and abandons a process requested by an erase or write instruction when the flag is set. An authenticator uses data in the confidential information area to execute an operation for authentication. A management information area may store management information for associated pages. The flag may include a bit string and a complementary bit string to improve reliability of the flag. The confidential information area may store dummy data when the memory is used for uses other than an application with an authentication function, so no problem arises using a normal controller.

主权项

1. A semiconductor memory device, comprising:
a memory which comprises an area accessible from outside and a confidential information area storing confidential information and a flag that is settable; a controller which reads the flag from the confidential information area when instructed to erase data at an address within the confidential information area, determines whether the flag is set, erases data in the confidential information area when the flag is clear, and abandons a process requested by the erase instruction when the flag is set; and an authenticator which uses data in the confidential information area to execute an operation for authentication, wherein the memory comprises an information storage area including pages storing data and a management information area displaying one-bit information for the management information for the pages with n-bit random data, n being a natural number, when the one-bit information is valid; and the controller determines whether random data is stored in the management information area, and determines that a corresponding bit of the management information is valid when random data is stored.