Encryption/decryption instruction set enhancement

Details Encryption/decryption instruction set enhancement Encryption/decryption instruction set enhancement

2007-08-07

2007-08-07

Smithers, Matthew (Department: 2137)

Cryptography

Particular algorithmic function encoding

Nbs/des algorithm

C713S189000

Reexamination Certificate

active

09419828

ABSTRACT:
A structure and associated method to implement encryption/decryption under the Data Encryption Standard (DES). Several additional instructions are included in the instruction set of a general purpose microprocessor to operate in conjunction with hardware included in a data path of the general purpose microprocessor. The additional instructions perform a portion of the DES algorithm, in particular, a portion of a DES round. The state information used at each step of the encryption portion of the DES algorithm is provided in various general purpose registers of the general purpose microprocessor. In one embodiment, all sixteen subkeys are selected prior to the DES step in the general processor after a DES key is known. In another embodiment, each subkey is selected during the round it is used. In yet another embodiment, each subkey is selected during the round it is used, as part of an additional instruction executed by the general purpose microprocessor.

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Schneier, Applied Cryptography, Protocols, Algorithms, and Source Code in C, 1996, John Wiley and Sons, Second Edition, pp. 270-277.
Data Encryption Standard (DES), Chapter 12, pp. 270-277, 1996.

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