Digital Fortress is a novel written by Dan Brown. Digital Fortress has many fun twists and mystical scenarios. The story begins with the introduction of Susan Fletcher, a cryptographer working at the NSA, and her boyfriend, David Becker, who is a language professor who likes to play squash. Trevor Strathmore is the head of the NSA's cryptography department and has found what he believes to be an unbreakable code, developed by a former NSA employee, Ensei Tankado. The NSA has a supercomputer called TRANSLTR that can crack any encrypted code in less than five minutes. Susan is called from Strathmore because there is an emergency. Strathmore tells Susan that TRANSLTR has been made obsolete. At first she doesn't believe him, but Strathmore shows Susan that TRANSLTR has been trying to crack the code for over fifteen hours. When Strathmore contacts Tankado to stop publishing, he refuses and Tankado places a free download on his website. However, no one can open the file until Tankado provides the password for the file, which is auctioned off to the highest bidder. He also threatens that if anything happens to him, an anonymous third party called "North Dakota" will release him to everyone. Tankado is later found dead in Spain, where Becker is sent to recover a ring he owned and what they think has the passcode to unlock Digital Fortress. In an effort to uncover Tankado's third-party partner before word spreads that Tankado is dead, Strathmore has Susan place a tracer on North Dakota's email account, or "ndakota," which has been set up on a server anonymous. Susan quickly discovers that Strathmore sent David to Spain. Strathmore believes Tanka... center of card... id and thinks David is dead. Strathmore fails to shut down TRANSLTR in time and it explodes, killing him. Susan manages to escape but is afraid for her boyfriend. The NSA director takes Susan to the main database, where the virus is attacking and everyone is trying to find the kill code. He tells everyone that the code is engraved on the ring David found, and the NSA director contacts the two agents who took David, and Susan sees her fiancé alive. They discover that the code doesn't work and Susan finds a puzzle in the program to turn it off. The code is number 3. They were able to discover it through the difference between the Hiroshima nuclear bomb, isotope 235, and the Nagasaki nuclear bomb, isotope 238. These were the bombs that killed Tankado's mother. The database is saved before any hacker can obtain confidential information.