| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a security device of small form factors which can be inserted into a telephone line in series for encrypting a dual tone multi-frequency (DTMF) tone from a telephone set in order to prevent the unjust disclosure of secret information. <P>SOLUTION: A receiving device decrypts a DTMF tone encrypted in order to receive original information sent over a telephone. A security device functions as a second factor in a two-factor authentication system using a security server of a telephone service for authenticating the security device. <P>COPYRIGHT: (C)2013,JPO&INPIT |
