Detecting rewriting of stored data, using codes based on password and the stored data

摘要

In storing data, a first code is generated by converting a password and some predetermined portion of the data itself (e.g., all of the data itself, or a time stamp) in a predetermined procedure. The first code is then stored in correspondence to the data. Thereafter, in reading the stored data, a second code is generated by converting the password and the same predetermined portion of the stored data, using the same predetermined procedure, and the resulting second code is compared with the first code stored in correspondence to the stored data. A determination is made that a rewrite has occurred, if the two codes do not match. Subsequent data processing may be controlled in accordance with the result of this determination.