Based on analyzing the genesis types and reservoir-forming course of the lithological trap in the deep sub-depression in downfaulted basin, reservoir-forming mechanism of lithological pool is subtle passage and episodic replacement.

Oil and gas migrated from source rock to sands,and formation water and the early filled hydrocarbon blew out of sands by subtle passage system.

Passage systems can be classified into fracture type, sand body type, unconformity type, and compound type by composition; into effective passage system, and high-effective passage system by validity; and into passage system, and subtle passage system by identification.

Recently, with exponentially growing demands for high security and reliable data transmission in applications of disaster early warning, military communication, network security, emergency communications, information hiding and interference cancellation, hidden data transmission has attracted a wide range of attention for its great importance, urgent needs and encouraging prospects.

The significance of concealed work,the main forms of concealing,causes of problems concerning concealed work,as well as means dealing with them are expounded.