Public-key cryptographic apparatus handling ciphertext by public

Details Public-key cryptographic apparatus handling ciphertext by public Public-key cryptographic apparatus handling ciphertext by public

1995-02-14

1996-11-19

Tarcza, Thomas H.

Cryptography

Particular algorithmic function encoding

Public key

380 28, 380 49, H04L 930

Patent

active

055771238

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.

REFERENCES:
patent: 4405829 (1983-09-01), Rivest et al.
patent: 4658094 (1987-04-01), Clark
patent: 5068895 (1991-11-01), Shimada
patent: 5301235 (1994-04-01), Shimada
IEICE Technical Report, published Jul. 13, 1992.
Okamoto, "An Introduction to the Cryptographic Theory", Kyoritsu Publishing Company, 1993, pp. 88-99.
M. Shimada et al., "Another Practical Public-Key Cryptosystem", Electronics Letters, 5th Nov., 1991, vol. 28, No. 23, pp. 2146-2147.
M. Shimada et al., "Blocking Method for RSA Cryptosystem without Expanding Cipher Length", Electronics Letters, 8th Jun., 1989, vol. 25, No. 12, pp. 773-774.
D. E. Robling Denning, "Cryptography and Data Security", Addison-Wesley Publishing Company, Inc. 1982.

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