| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To prevent safety of encryption from being lowered even when a number of plain texts in which a head part tends to become the same, are encrypted. <P>SOLUTION: A dummy letter selection means 1b selects one or more letters as dummy letters, which are located in a predetermined position of an input plain text 3. An encryption means 1a encrypts the selected dummy letters according to an encryption using mode including a concatenation function, and updates a register value on which an initial vector is set beforehand. Then, the encryption means 1a further encrypts the plain text 3 by using the updated register value. An encryption output means 1c outputs an encryption processing result for the plain text 3 by the encryption means 1a, as an encryption text 4. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
