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.

Date of Patent:
Aug. 28, 2001

Filed:

Mar. 12, 1998
Applicant:
Inventors:

Yoshinao Kobayashi, Hiratsuka, JP;

Nobuyuki Oba, Sendai, JP;

Seiji Munetoh, Tokyo-to, JP;

Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H04L 9/00 ;
U.S. Cl.
CPC ...
H04L 9/00 ;
Abstract

An output bit sequences is derived from an initial bit sequence and this output bit sequence is used to encrypt an input bit sequence in a first mode of operation or not to so encrypt the input bit sequence in a second mode of operation. The mode of operation is switched automatically whenever the output bit sequence contains a predetermined trap bit sequence. As a result of this automatic switching between such encryption and no such encryption, unauthorized determination of secret codes is thwarted.


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