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:
Mar. 04, 1997
Filed:
Aug. 30, 1995
Thomas H Likens, Fort Worth, TX (US);
Matthew H Childs, Arlington, TX (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
A method of securely testing a cryptographic device need not be carried out in a secure testing facility by cleared personnel. First, a test cycle total count number is provided. Then, for each of a plurality of test cycles, the number being determined from the test cycle total count number, an input data signal is provided to the cryptographic device. The input data signal is encrypted to determine an encrypted signal, and the encrypted signal is then decrypted to determine a decrypted signal. Finally, the input data signal is compared to the decrypted signal. A cryptographic device includes receiving circuitry for receiving the input data signal and encryption circuitry that encrypts the input data signal to determine the encrypted signal. Decryption circuitry decrypts the encrypted signal to determine a decrypted signal, and comparing circuitry compares the input data signal to the decrypted signal. Finally, sequencing circuitry causes a plurality of input data signals to he sequentially provided to the receiving circuitry during a plurality of test cycles, one input data signal per test cycle.