Cryptography – Key management – Having particular key generator
Reexamination Certificate
2005-04-07
2010-02-09
Pich, Ponnoreay (Department: 2435)
Cryptography
Key management
Having particular key generator
C380S277000, C380S046000, C708S250000, C708S255000
Reexamination Certificate
active
07660414
ABSTRACT:
In the encryption/decryption method, a random number sequence {ri} is generated on the basis of a given multiple-affine key system K and encryption is performed by an exclusive OR of the random number sequence {ri} with a plain text. Further, the multiple-affine key system K is automatically sequentially rewritten into a series of new multiple-affine key systems each time when the number of use times of the multiple-affine key system reaches a predetermined number and encryption of plain texts thereafter is continued while generating random numbers using the series of the rewritten multiple-affine key systems. Likewise, in decryption as well, since decryption is performed using a multiple-affine key system automatically rewritten each time when the number of use times reaches a predetermined number, a third party cannot reproduce the multiple-affine key system and therefore cannot decipher a cipher text.
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Fujisoft ABC Inc.
Oblon, Spivak McClelland, Maier & Neustadt, L.L.P.
Pich Ponnoreay
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