The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 05, 2002
Filed:
Nov. 14, 1997
Mark E. Bianco, Pomona, CA (US);
Raytheon Company, Lexington, MA (US);
Abstract
An in-line decryptor is employed to decrypt software (program instructions) transferred from a read only memory to a central processing unit. The in-line decryptor comprises a keystream generator that contains a cryptographic algorithm coupled to a memory that stores cryptographic keys. A combining function implemented using two substitution functions and two XOR functions generates an output keystream of the keystream generator. The decryptor uses the cryptographic algorithm to initialize a variation of a one time pad cryptosystem. Using a number of relatively short pseudorandom sequences and a simple combining function, a much longer address-dependent pseudorandom sequence is created. This sequence is used to decrypt the encrypted software in real time on an instruction-by-instruction basis.