Network;
Research;
Center,;
Tsinghua;
University,;
Beijing;
100084,;
China;
Tianjin;
Key;
Laboratory;
for;
Advanced;
Signal;
Processing,;
Civil;
Aviation;
University;
of;
China,;
Tianjin;
300300,;
China;
Information;
Security;
Center,;
Beijing;
University;
of;
Posts;
and;
Telecommunications,;
Beijing;
100876,;
China;
信息隐藏; 语音信息; 信息安全; 公共开关电话网络; PSTN;