Variable-length key cryptosystem

Details Variable-length key cryptosystem Variable-length key cryptosystem

2007-05-29

2007-05-29

Vu, Kim (Department: 2135)

Cryptography

Communication system using cryptography

Data stream/substitution enciphering

C380S259000, C380S277000, C380S043000

Reexamination Certificate

active

10105219

ABSTRACT:
A variable-length key cryptosystem is provided, in which the amount of parameters for generating a key to be shared is small, security is high, and calculation cost is small.The length of a plain text inputted from a data input part10is detected by a data string length detection processing part20. A variable-length key generation processing part30generates an encryption key with a required arbitrary length, using an initial character string and a conversion rule, based on the length of a plain text. A conversion character string generation processing part32generates a converted character string from an initial character string by applying a conversion rule of increasing the length of a character string. Conversion is conducted until the length of a plain text is reached. An encryption key is not used twice. Therefore, an unused conversion character string is searched for, and a stream code processing part40generates an encrypted text by using a generated encrypted string. A receiver system200generates a converted character string from an initial character string by the same conversion, based on the length of an encrypted text, thereby obtaining the same encryption key.

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Communication from European Patent Office of Jun. 28, 2004.

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