| 摘要 |
PROBLEM TO BE SOLVED: To avoid an attach of an LLL method and to improve the sefety by constituting a ciphering sentence employing a plain sentence vector, in which the plain sentence that is to be ciphered is divided, and an inner product of a random number vector, that is not especially required to be ciphered, and a base vector. SOLUTION: First, a base vector B is set using a secret key at an entity (a) side. Base on a public key, a plain sentence (x), that is to be ciphered and transmitted, is J divided to obtain a plain sentence vector (m). Moreover, a random number vector (r), that is not necessarily transmitted, is obtained. Then, a message vector (m') having K elements is obtained by coupling the vectors (m) and (r). Thus, the vector (m') is expressed as integers using the vector B. Then, an inner product of the vector (m') and public key vector (c) is obtained, the vector (m') is ciphered and a ciphered sentence C is obtained. The generated sentence C is transmitted to a receiving side entity (b) from the transmitting side entity (a) through a communication path 3. |
