| 摘要 |
PROBLEM TO BE SOLVED: To provide a public key ciphering system in which a normal user easily deciphers, while maintaining safety of ciphering. SOLUTION: Let Cs be a matrix of M rows and N columns, having two elements '1' in every row, Cn be a reversible matrix of M rows and M columns, having two elements '1' in every row and D be a reversible matrix of N rows and N columns. Then, a plain sentence vectorξis multiplied by a matrix Cn-1CsD and a random vectorξ, in which the appearance probability of '1' is (p), is added to obtain a ciphered sentence (z). Note that the matrix Cn-1CsD and the value (p) are public keys and Cn, Cs and D are secret keys. During deciphering, the sentence (z) is multiplied by the matrix Cn to obtain a vector (b), a parity inspection equation b=Cs S+Cnτis solved, with respect to vectors S andτ, by using a probabilistic search method such as a brief propagation, and an estimated value of a plain sentenceξis obtained by multiplying D-1 to the vector S.
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