Patent ID: 6731754
Filing Date: 2004-05-04
Classification: H04L

Abstract:
A coding method for an information secrecy security system designed for transmitting and storing the contents of plain-texts converted into a form of digital information while securing secrecy of the contents thereof, the method comprising:coding a plain-text signal Pi of a predetermined number of bits into a unit block of a coded signal using a feedback coding method, the feedback coding method comprising: using a coding Latin square L as a conversion table for a converter component of a coder in said coding method; using a plain-text signal Pi and an initial value signal in a first conversion; using the plain-text signal Pi and a coded signal Ci, which is converted from a preceding plain-text signal Piâˆ’1, in a second and subsequent conversions as a feedback signal Cb to specify row and column positions of said coding Latin square L; and using a value corresponding to the specified positions as a coded signal Ci; and decoding using the coded signal Ci as a unit block using feedforward decoding method, the decoding method comprising: using a decoding Latin square Lâˆ’1, corresponding to said coding Latin square L, as a conversion table for a converter component in a decoder according to said feedforward decoding method; using coded signal Ci and an initial value signal, which is the same as that used for coding, in the first conversion; and using said coded signal Ci and a preceding coded signal Ciâˆ’1 as a feedforward signal Cf in the second and subsequent conversions to convert the value obtained from said decoding Latin square Lâˆ’1 into a decoded plain-text signal Pi, wherein the converter decoding Latin square Lâˆ’1 into a decoded plain-text signal Pi, wherein the converter component comprises a plurality of coding Latin squares and a plurality of decoding Latin squares, and wherein, said plurality of Latin squares are selectively used by being switched according to a predetermined sequence synchronized with input of the plain-text signal Pi or the coded signal Ci.