Storage medium and method and apparatus for separately protecting data in different areas of the storage medium

Abstract

Disclosed are a method and an apparatus for protecting data on a storage medium by encrypting the data to be recorded on the storage medium with a password. This method comprises a step of, generating, for changing key data on each memory unit by one password, the key data, thereafter encrypting the key data with the password and writing the encrypted data to the storage medium, and a step of encrypting the data with the key data and encrypted data to the storage medium. The method further comprises a step of reading the encrypted key data from the storage medium, a step of decoding the encrypted key data with the password, and a step of decoding the data on the storage medium with the decoded key data. The encryption is done by using the key data generated separately from the password, and it is therefore feasible to prevent the password from being analyzed by decoding a cipher text.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a method of and an apparatus for protecting data on a storage medium, which are intended to protect the data to be recorded on the storage medium by encrypting the data with a password, and to the storage medium thereof in an information processing appliance. [0003] 2. Description of the Related Art [0004] A storage device utilizing an optical disk, a magnetic disk and an IC card etc, is utilized for a variety of information processing appliances such as a computer, a word processor and an electronic book etc. Information such as information related to privacy and confidential information in terms of duties, which should not be known by persons other than an owner, might be written to this type of storage device. It is required that the data be encrypted in order to make such information unknown by others. [0005]FIG. 15 is an explanatory diagram showing the prior art. [0006] A passwo...

AI Technical Summary

Benefits of technology

[0016] It is still another object, of the present invention to provide a method of and an apparatus for protecting data on a storage medium, wherein re-encryption of data is not needed even when a password is changed.

[0019] Thus, the data is encrypted by use of the key data generated separately from the password, whereby the encrypted key data is, even if a cipher text is to be analyzed, merely decrypted. The password and the key data are therefore hard to be analyzed. This makes it feasible to prevent the password from being deciphered by analyzing the cipher text.

[0020] Further, since the encryption is done using the key data generated separately from the password, a key different based on the memory unit such as a sector etc can be imparted to one password by changing the key data. Consequently, the encryption can be accomplished by use of the key different per logic sector, whereby a data confidentiality can be enhanced.

[0021] Furthermore, the encryption is carried out by using the key data generated separately from the password, and therefore, even if the password is changed, the data is not required to be re-encrypted. Hence, the password can be easily changed on even a storage medium having a capacity as large as several hundred mega bytes.

Problems solved by technology

There arise, however, the problems inherent in the prior art.

Accordingly, a conventional method of encrypting with the same password on the storage medium presents such a problem that if a volume of the cipher texts is large enough to make a statistic process executable, the characteristics of the plain texts can be presumed easily.

A problem peculiar to the conventional method of encrypting with the same password on the storage medium is that the password is presumed by analyzing this portion, in which case other vital data are to be deciphered.

This operation is troublesome and might cause a problem in which a fault such as forgetting the password and so on is easy to occur.

Accordingly, the problem is that the password is easy to be presumed from the cipher text.

A fifth, problem is that the data has hitherto been encrypted directly with the password, and hence, if the password is changed, the whole data are required to be re-encrypted.

Images