| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To encrypt a character code without changing data length. <P>SOLUTION: When a plaintext 3 is input, character codes contained in the plaintext 3 are converted into numeric values by a plaintext encoding means 1b. Then, the numeric values for each character code obtained by the plaintext encoding means 1b are successively obtained by an encryption means 1d and, by using the value of a register 1c whose initial value is set, the first numeric value is encrypted into an cryptographic value of the same number of bits. After this, the update of the register value using at least a part of the numeric value obtained by the encryption and the encryption of the numeric value using the updated register value are alternately repeated, and all the input numeric values are encrypted. Then, by a character code generation means 1e, each cryptographic value obtained by the encryption means 1d is converted into a character code and a ciphertext 4 is generated. <P>COPYRIGHT: (C)2007,JPO&INPIT</p> |
