Data encryption device and memory card
AssigneeSharp Kabushiki Kaisha
InventorShigeo Ohyama
Life of this patent
Estimating the term…
Abstract
A data encryption device performs high-speed access to an arbitrary page when encrypting data and writing it to a storage device that can be accessed in a page unit or reading data therefrom and decrypting it. The device: encrypts data and writes it to the storage device or reads data from the storage device and decrypts it by a stream cipher; uses a counter mode of a block cipher to generate pseudorandom number series; specifies a data position in the storage device based on a page number and a page block number, by dividing one page into plural page blocks having a block length of the block cipher; and uses a value determined by a function of the page number, the page block number, and an arbitrary offset value, as an initial value of a pseudorandom number to be used in the counter mode.
Claims6
A data encryption device that
- encrypts data to be stored in a storage device by a stream cipher and writes the encrypted data to the storage device, or reads the encrypted data from the storage device and decrypts the read data by the stream cipher, the storage device being accessed in a page unit, and
- uses a counter mode of a block cipher to generate pseudorandom numbers for encryption or decryption, wherein
- the page is divided into a plurality of page blocks that have the same block length as a block length of the block cipher, and encryption or decryption is performed in a counter mode of the block cipher in the divided page block unit,
- a position of the data to be written or read in the page is specified by a page block number of each of the page blocks, and
- a value obtained by a function of a page number and the page block number of the page to be written or read, and an offset value which is constant in encryption or decryption but different for each data encryption device is used as an initial value for generating each of the pseudorandom numbers.
A data encryption device that encrypts data to be stored in a storage device by a stream cipher and writes the encrypted data to the storage device, or, reads the encrypted data from the storage device and decrypts the read data by the stream cipher, the storage device being accessed in a page unit, comprising:
- a pseudorandom-number generating circuit to generate a pseudorandom number in a counter mode of a block cipher,
- an initial-value generating circuit to generate an initial value for generating the pseudorandom number,
- an exclusive OR circuit, the exclusive OR circuit outputting a cipher text by performing exclusive OR of a plain text by performing exclusive OR of a cipher text and the pseudorandom number, wherein
- the page is divided into a plurality of page blocks that have the same block length as a block length of the block cipher, so that a position of the data to be written or read in the page is specified by a page block number of each of the page blocks,
- the initial-value generating circuit generates the initial value for each of the page blocks, as a function of a page number and the page block number of the page to be written or read, and an offset value which is constant in encryption or decryption but different for each data encryption device, and
- the exclusive OR circuit performs an exclusive OR operation for each of the page blocks.
Dependencies are inferred from the claim text.