Navy divers have begun searching for "black boxes" containing classified electronic equipment that was on a satellite that was to have been launched by the space shuttle Challenger, Navy and NASA officials said today.

The boxes were described by NASA officials today as "encryption" or scrambling devices, used to secure voice and computer communications between the space shuttle and ground controllers.

As Navy salvage ships resumed their search for Challenger debris following several days of rough weather this week, officials said new emphasis has been placed on finding the black boxes.

A NASA spokesman said rough seas and gusty winds continued to hamper recovery efforts today. In addition, salvage operations were set back when a line to one of the unmanned sonar submarines snapped.

Most of the wreckage of the shuttle's crew cabin containing the remains of the astronauts has been recovered, but salvage teams have been unable to locate significant portions of the shuttle's critical right solid-rocket booster that is thought to have caused the Jan. 28 explosion, officials say.

Capt. Charles Bartholomew, Navy supervisor of salvage operations, said the classified black boxes are the next priority in the operation. Divers are searching a shallow area about 14 miles offshore.

The black boxes were aboard a $100 million satellite that was supposed to have become part of the space agency's Tracking and Data Relay Satellite System (TDRSS.)

Dale Harris, project manager for TDRSS, said the satellites relay communications between the shuttle and NASA's White Sands Test Facility in New Mexico. One TDRSS satellite is in orbit, and there are plans for two more with a fourth as backup.

As part of this system, voice and data from the shuttle are scrambled by the TDRSS black boxes and decoded at the White Sands facility.

"You're heard about computer hacks breaking into systems," Harris said. "These are critical national resources, and we don't want anybody in there just fooling around."