Cryptographic accelerator

Details Cryptographic accelerator Cryptographic accelerator

2001-08-14

2004-12-14

Morse, Gregory (Department: 2137)

Cryptography

Particular algorithmic function encoding

C380S029000, C380S037000, C380S259000, C713S189000

Reexamination Certificate

active

06831979

ABSTRACT:

BACKGROUND
1. Field
The present invention relates to the field of cryptography. More particularly, the present invention relates to a cryptographic accelerator.
2. General Background
Over the last decade, computers have become an important product for both commercial and personal use, in part due to their versatility. For example, computers are commonly used as a vehicle to transfer information over a communication link such as private networks or public networks. “Private networks” include any network having restricted access (e.g., a local area network), while “public networks” include any network allowing access to the public at large such as the Internet for example. In many situations, it may be desirable to encrypt digital information prior to transmission over the communication link so that the transmitted information is clear and unambiguous to a targeted recipient, but is incomprehensible to any illegitimate interlopers.
In 1981, the National Institute of Standards and Technology approved a data security process referred to as the “Data Encryption Standard.” The Data Encryption Standard (DES) details the use of a cryptographic function, referred to as a “Data Encryption Algorithm” (DEA), for encrypting and decrypting digital information by a single, unique key. To ensure security of the transmitted information, the nature of the key is held in confidence between the source and the targeted recipient. DES and DEA are described in a Federal Information Processing Standards Publication 46-2 (FIPS PUB 46-2) entitled “Data Encryption Standard (DES)” which was published on or around Dec. 30, 1993.
In general, DEA features three (3) types of cryptographic operations; namely, bit permutations (or sometimes referred to as bit swapping), exclusive-OR (XOR) operations and table lookups. A “bit permutation” is a transposition of bits such that a bit pattern of input information differs from the bit pattern of output information. While XOR operations and table lookups can be adequately performed by software, bit permutations are more difficult to replicate in software.
Concise software code for emulating bit permutations is difficult to produce because there is no mathematical relationship between the input bit pattern and the output bit pattern. Instead, to achieve transposition, sub-programs are coded to test individual bits in the input pattern and then set reset bits in the output pattern, which greatly increases the number of instructions needed for a software implementation of DEA as shown in Table A.
TABLE A
NUMBER OF
PROCESSOR
OPERATIONS PER
INSTRUCTIONS
DES OPERATION
ENCRYPTION
PER OPERATION
Initial Permutation
1
128
Reverse Initial Permutation
1
128
Key Bit Selection PC-1
1
112
Key Rotate
16 
 96
Key Bit Selection PC-2
16 
1792 
XOR
16 
 16
E-Bit Selection
16 
256
S Table Lookup
128 
128
Bit Permutation
16
1024 
Total
3680 
As a result, encryption/decryption software in accordance with DEA is slow and costly due to increased programming costs and increased memory size to accommodate the complex software. Hence, it would be desirable to create a cryptographic accelerator which includes hardware to perform bit permutations and other instruction intensive operations while other operations are performed by software as normal. This would avoid substantial modification of current electronic systems and enhance the speed of the cryptographic accelerator.
SUMMARY
Briefly, one embodiment of the present invention includes a cryptographic accelerator comprising (i) a selector and (ii) a plurality of buses coupled to the selector. Herein, at least one of the plurality of buses includes signal lines routed to perform a bit permutation operation on incoming information. The bit permutation operation is one of a plurality of operations associated with a symmetric key function.


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