This vault is ground zero for law enforcement's battle to unlock encrypted smartphones

Just off the main corridor of the Manhattan cyber laboratory, protected by a heavy steel door, is a small chamber where some of the lab’s most consequential work is carried out in isolation.

About 100 locked cell phones, seized in various criminal investigations, are stacked neatly on two shelves. Nearby, computers silently batter the devices with spurts of numerals as they attempt to guess the passcodes.

Only when the lights are off is the work visible, in flashes of blinking lights.

Success can come in minutes, hours, days or months. Or not at all.

Of the 1,035 devices that were locked on arrival at the lab last year, 405 remain inaccessible, according to lab records. The year before, 666 of the 1,047 locked phones could not be opened.

New batches of phones are moved into the chamber like unbaked cookies. Others are moved out before they’re done.