Device for enciphering and deciphering, by means of the DES algorithm, data to be written to be read from a hard disk

Apparatus for enciphering and deciphering data to be written to and read from a hard disk, the apparatus comprising:

• a processor;
• a hard disk storage unit;
• and
• an encryption/decryption circuit connected between the processor and the hard disk storage unit for enciphering and 8 deciphering data through a data encryption standard (DES) algorithm, the encryption/decryption circuit having:
• a first converter circuit for converting n-bit wide words applied as an input thereto (wherein n is an integer less than or equal to 64) into 64-bit wide words, said n-bit words incoming, via a first n-bit wide bus, from the processor and intended for storage in the hard disk storage unit or incoming, via a second n-bit wide bus, from the hard disk storage unit and intended for application to the processor;
• a DES cipher circuit, connected to and responsive to the converter and through use of the DES algorithm, for enciphering each of the 64-bit words, formed of n-bit words incoming from the processor, into corresponding 64-bit DES encrypted words and for deciphering each of the 64-bit words, formed of n-bit words incoming from the hard disk storage unit, into corresponding 64-bit DES decrypted words;
• and
• a second converter circuit, connected to the DES cipher circuit, for converting each of the 64-bit DES encrypted words into n-bit encrypted words and for applying, via the second n-bit bus, each of the n-bit encrypted words to said hard disk storage unit for storage thereon, and for converting each of the 64-bit DES decrypted words into n-bit decrypted words and for applying, via the first n-bit bus, each of the n-bit decrypted words to the processor.