|"[G]overnment surveillance of electronically stored information on the private lives of citizens, and the possible civil liberties and ethical implications of using such technology" (Wikipedia)
Susan Fletcher, star of the NSA's cryptography division, is called in by NSA Deputy Director Trevor Strathmore after TRANSLTR, the NSA's code-breaking computer, encounters a code that it can't break. This code, called Digital Fortress, was created by Ensei Tankado, a disgruntled NSA operative. When Tankado is found dead in Seville, Spain, Strathmore dispatches David Becker, Fletcher's fiancée, to investigate in the hope of finding a clue to breaking the code, while Fletcher and Strathmore investigate Tankado's mysterious partner "North Dakota", who unknown to them is in talks with a Japanese corporation to release the Digital Fortress code publicly. But as in any Dan Brown novel, all is not as it seems...
As with any Dan Brown book, Digital Fortress is infamous for some lapses of research, particularly some glaring flaws in its portrayal of cryptography and its portrayal of Seville as a poorly equipped city, with a medical service almost as bad as some in third-world countries. Despite this, it remains a readable book if you keep the MST3K Mantra in mind (though opinions differ on this point).
- Anti-Villain: Ensei Tankado. Sure he conspired to infect the NSA's computer with a virus that would remove all its protection from hackers, but he never intended to let it actually happen, just force them to admit they really did have a big shiny computer and he wasn't spreading anti-US propaganda about 60 years too late.
- As Long as It Sounds Foreign: Ensei Tankado is not a real Japanese name.
- Attempted Rape: Subverted twice. Susan thinks Hale's about to rape her, and David gets maced when a girl thinks he wants to hire her as a prostitute, then Strathmore actually does try to rape Susan.
- Batman Gambit / Kansas City Shuffle: Tankado's "unbreakable code" is a virus that he tricked the NSA into downloading into their system so he can hold the NSA database to ransom and force the NSA to admit the existence of TRANSLTR.
- Big Bad: Strathmore
- Big Brother Is Watching: Except in this story, Big Brother are the good guys.
- Clear My Name: Tankado's entire Batman Gambit
- Cool Plane: David gets to ride in one for his trouble twice.
- Corrupt Corporate Executive: The Japanese businessman who Strathmore plans to sell/distribute the modified digital fortress encryption protacol (with a back door) to.
- Dan Browned: Trope Namer
- Did Not Do the Research: Cryptography (particularly brute force attacks), viruses, databases, the Kingdom of Spain in general and the city of Seville in particular.
- Embarrassing Nickname: Hale is called "Halite" by his colleagues (he doesn't realize this is embarrassing though).
- Hollywood Hacking: Throughout the whole book (Read: mutation strings), but particularly egregious in the climax: The clue that leads them to discover the password to shut off the virus is discovered by looking through the source code for "orphaned strings". It's impossible for them to have the source code to the virus; if they did, their hunt to "decrypt" Digital Fortress would have been redundant. They would have been able to see what it could do and add their backdoor whenever they felt like it. Maybe they were looking for his compiler?... Averted, surprisingly, when they look at the worm's operating commands: if they were loaded into memory and they still had the ability to view their memory registers, they actually could interpret its instructions. Of course, figuring out machine code would probably take a significant chunk of time, but this is the NSA we're talking about here.
- I'm Dying, Please Take My MacGuffin: A subversion. A character takes what looks like the MacGuffin off a dying character, but actually, the character was signalling the decryption code with their fingers.
- Informed Ability: The main character's intelligence.
- Love Makes You Crazy: Strathmore orders the death of David Becker so he can have Susan for himself.
- McGuffin: Tankado's ring, which everyone believes has the Digital Fortress decryption code on it. In the end, it turns out it doesn't.
- Mistaken for Gay: Becker, briefly at the hotel.
- Mistaken for Junkie: At first David believes that the girl who has the ring is one.
- Murder the Hypotenuse: Strathmore's plan.
- My Country, Right or Wrong: Tankado went through a historical version in the backstory; as a child he was upset that the US used nukes on his country (and that he suffered deformities which caused his mother to die in childbirth and his father to abandon him), later in life he decided Japan was as at fault as the USA in WWII, dropped his grudge and even began working for the US government.
- The protagonists fit this trope as well, being NSA employees who are perfectly fine with all manner of immoral or even outright illegal things as long as it's in the national interest (they occasionally monologue about it).
- My God, What Have I Done?: The final chapter has the corrupt CEO discover Tankado, the man he'd practically ordered the death of for profit, was the deformed son he walked out on.
- Nice Job Breaking It Strathmore: While he may not be that heroic, Strathmore having Tankado murdered ruins the latter's plan...by turning his casualty free plan for vindication into a full on attempt to destroy the NSA's giant shiny computer and let any interested hackers march straight into their data system.
- Playful Hacker: Greg Hale was somewhere in between this and The Cracker (on the one hand, he causes damage and has a political agenda, on the other hand said damage was discovering an illegal backdoor the NSA planted in some encryption software).
- Psycho for Hire: As is traditional for a Dan Brown book, we have an assassin with a Red Right Hand in Hulahot, the assassin hired by Strathmore to kill Tankado and David Becker and recover the Digital Fortress key.
- Recruiting the Criminal: How Hale was originally hired. While what he did-- find a back door they left in an encryption algorithm-- wasn't exactly illegal, it certainly did negatively impact his future employers. Possibly Tankado as well, considering he was quite anti-American before he got over the Hiroshima and Nagasaki bombings (although he didn't get around to committing any crimes because of it).
- Red Shirt: The computer tech who turns comes in by chance and gets suspicious. Also the assassin following David kills everyone he speaks to when he's left.
- Red Herring Mole: Greg Hale, who Susan believes is North Dakota. He is sadly (or not) Acquitted Too Late.
- Significant Anagram: NDAKOTA is an anagram of Tankado, which is a clue to the fact that there is no North Dakota.
- Spanner in the Works: Strathmore ruins Tankado's plan when he has him killed, almost dooming the NSA database to destruction because Tankado can't give them the code to deactivate his virus. Fortunately the NSA figure out the code themselves before it's too late.
- The Password Is Always Swordfish: Tankado's password is the single digit '3'. He even leaves clues just to make absolutely sure that everyone can guess it. Possibly justified in that Tankado may have wanted them to guess it. Which begs the question of why he even bothered with a password in the first place.
- Since he was trying to ransom the password off and he expected to be alive to give it to them and clearly didn't expect them to guess it (it's made quite clear that the fact he's dying is a massive Oh Crap moment for him), it's fair to assume that we're supposed to believe this is an absolutely, positively fiendishly clever password with the clue being there to taunt them.
- Brown Fails Physics Forever, since the "difference" in the clue is not 3. Also, it's axiomatic that cryptosystem security is exponentially proportional to key length. This key is approximately 8 bits long. Good job, guy.
- Viewer-Friendly Interface: A rare literary example.
- Who Watches the Watchmen?: The entire conflict is down to Tankado feeling that TRANSLTR gives the NSA too much control and not enough oversight (since they decided to just use it to decrypt everything they could find rather than go through some sort of requisition process). He's quite fond of the orinal Latin phrase as well and it's what's engraved on his ring, rather than the passcode as everyone assumed. Hale also seems to think about this a lot.