| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a technology for simply and quickly verifying whether a key can correctly decode cipher text data, when encrypted data (cipher text data) and the key are given. <P>SOLUTION: The cipher text data c1 generated by ciphering plain text data using an encryption key, encryption data smaller in size than the cipher text data c1, and the cipher text data c2 generated by ciphering the verification data using the encryption key are obtained (S601). Whether a result obtained by decoding the cipher text data c2, using a decoding key, agrees with the verification data (S607) is determined. When it is determined that they agree, the cipher text data c1 is decoded by using the decoding key (S608). <P>COPYRIGHT: (C)2009,JPO&INPIT</p> |
