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:
Nov. 19, 1996
Filed:
Feb. 14, 1995
Michio Shimada, Tokyo, JP;
NEC Corporation, Tokyo, JP;
Abstract
The invention provides a public-key cryptographic apparatus which does not leak information regarding a plaintext and can prevent an increase in block length. A quadratic residue calculation circuit calculates a residue when the square of the lower n-1 bits of the plaintext of n bits is divided by public-key, and an exclusive OR circuit calculates an exclusive OR of the least significant bit of a result of the calculation and the most significant bit of the plaintext. Then, public-key encipherment such as the RSA cryptosystem or a modified Rabin cryptosystem is performed twice repetitively for totaling n bits of the output of exclusive OR circuit and the lower n-1 bits of plaintext by public-key enciphering circuits so as to make it impossible to estimate the most significant bit of the plaintext from the ciphertext.