1. The novel focuses on the NSA's efforts to break an unbreakable encryption code called Digital Fortress, which threatens to cripple U.S. intelligence if not cracked.
2. The code was created by former NSA cryptographer Ensei Tankado as a protest against government overreach into citizens' privacy.
3. The story follows cryptanalyst Susan Fletcher's attempt to find Tankado's partner who holds the key to cracking the code, pitting national security against civil liberties.