Digital Fortress
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Image:Digital fortress.jpg Digital Fortress is a novel by American author Dan Brown and published in 1998 by St. Martin's Press (ISBN 0312263120).
Contents |
Plot
Susan Fletcher, a brilliant mathematician and head of the National Security Agency's cryptography division, finds herself faced with an unbreakable code resistant to brute-force attacks by the NSA's 3 million processor supercomputer. The code is written by Japanese cryptographer Ensei Tankado, a sacked employee of the NSA, who is displeased with the agency's intrusion into people's privacy. Tankado auctions the algorithm on his website, threatening that his accomplice, "NDakota", will release the algorithm for free if he dies. Tankado is found dead in Seville, Spain. Fletcher, along with her fiancé, a skilled linguist with eidetic memory, must find a solution to stop the spread of the code.
Main characters
- Susan Fletcher: Mathematician, NSA's head cryptographer
- David Becker: Professor of Linguistics at Georgetown University and Susan's fiancé
- Trevor Strathmore: Deputy Director of the NSA, head of Crypto
- Ensei Tankado: Ex-NSA cryptographer, author of the virus Digital Fortress
- Greg Hale: NSA cryptographer, ex-marine
- Leland Fontaine: Director of the NSA
- Midge Milken: NSA's Internal security analyst
- Hulohot: Assassin hired to hunt down Ensei Tankado and take the ring. After killing Tankado, his new mission was to retrieve the ring before David Becker gets it.
- Chad Brinkerhoff: PA of the NSA Director's Office
- Phil Chartrukian: NSA Sys-sec
- Tokugen Numataka: Japanese businessman, Ensei Tankado's father
- Jabba: Anti-Hacker computer expert
Artistic license
Image:Nsa-enigma.jpg The main premise of the book is that there exists a supercomputer that can decrypt any encrypted message through brute force, no matter which algorithm was used to encrypt the message. No exotic cryptographic breakthroughs are mentioned. In reality this is a flawed premise, and one which characters repeatedly describe as being based on the "Bergofsky Principle". In fact, no such principle exists. Some algorithms such as the one-time pad are decisively impossible to decrypt through brute force alone. While there are widely used encryption methods that can be defeated through brute force attacks, most of them require decryption systems that have several orders of magnitude more computing power than that described in the novel, if the messages are to be decrypted in such a short timespan. The author also fails to account for exponential increases in difficulty as the key length increases.
It is possible to examine even an executable program without running it; as such, in reality viruses pose no problem to decryption systems, since they will never be running the text being decrypted. Since viruses are one of the key dangers in the book and a major plot point, this forms another major use of artistic license.
The novel states that "Enigma was history’s most famous code-writing machine—the Nazis’ twelve-ton encryption beast." In reality, the Wehrmacht Enigma weighed only around twelve kilograms.
The author has also stated that the ASCII consists of 256 characters, when it actually consists of 128 characters. He also stated that a 64-bit integer would make 64 characters. In reality, it can hold a value from 0 - 18446744073709551615 (264 - 1) or a range of 8 characters. Although ASCII only needs 7 bits per character, in practice an extra bit per character is left unused, so each ASCII character effectively consumes 8 bits.
The author uses some concepts as if they were encryption algorithms that can be broken by brute force: PGP, Diffie-Hellman, ZIP, IDEA, and ElGamal. Of these, Diffie-Hellman is a key exchange protocol which allows two parties to establish a shared secret key over an insecure communications channel. ZIP is a file format for data compression. PGP is an e-mail security program which uses the IDEA encryption algorithm, among others. The only two encryption algorithms of the list are IDEA, a symmetric encryption algorithm, and ElGamal, an asymmetric encryption algorithm.
The book also employs invented and undefined encryption technologies such as "mutation strings." Where real terms are used, they are thrown about without regard for their actual meaning. One section describes public-key encryption as using an agreed-upon key phrase, when in fact the defining feature of public-key systems is that they do not require shared secrets.
Towards the end of the book there is a claim that Fat Man, the nuclear bomb dropped on Nagasaki, contained no plutonium but instead was a uranium-238 bomb. While U-238 was present in Fat Man, it was only used as a tamper with the plutonium providing the main nuclear reaction. Uranium-238 cannot be used alone for fission.
At one point, an underground chamber is described as having a 40-by-30 foot video wall at one end, and having been built by excavating 250 metric tons of earth. Assuming the earth to be of average density, the room would be less than 2 metres long.
Contrary to the book's claim, it is not possible to trace the address to which an email is forwarded once it is sent (at least, not without cooperation from the recipient).
Five-character alphanumeric passwords are not considered secure. While an NSA cryptographer might use a weak password under some circumstances, she certainly would be aware of its weakness, and not be especially surprised if someone broke it.
Once a file has been downloaded, changing the contents of the file at the website will not normally affect any downloaded copies; this makes Strathmore's plan unworkable.
Image:SevillaGiralda.jpg Much of the depiction of Seville regarding places, buildings and population is also written under artistic licence. In reality the Giralda has ramps, not dangerous stairs; Plaza de España does not have the city hall but rather the Government Delegation, Subdelegation and other public buildings; punkers are scarce in Seville; Christopher Columbus is not venerated as a saint in Spain and his remains (which consist of skeletal pieces, the scrotum disappears in a cadaver 5-6 years after death) are buried intact in the Seville cathedral. Practically all the sentences about customs, religion, health care, telecommunications, transport, crime fighting and politics in Spain are inaccurate. The book is full of strange affirmations, for example that the typical Spanish drink is cranberry juice with vodka, or all the roma women of Seville are red-haired prostitutes "with a sexy latin accent". Brown also confuses, on a number of occasions, the Guardia Civil with the Spanish Urban Police and depicts all its agents as highly corrupt and violent.
Even the time of construction and artistic style of several monuments in Seville are wrong. For example, the book claims that the Giralda is a moorish tower from the 15th century with a height of 419 ft (140 m.), when it is actually an ancient almohad minaret of 320 ft (97.5 m.) built in 1184. The Seville cathedral, depicted as a 11th century gothic structure, was built between 1433 and 1528 over the ruins of a mosque and has several baroque, neoclassic and neogothic parts due to subsequent reforms. The Alcázar Real was started in the year 913 rather than the 15th century. Finally, the Hotel Alfonso XIII is not a small 4-star hotel, but a great 5-star hotel that was built in 1928 with the intention of becoming the most luxurious hotel in Europe.[1]
Unbreakable codes
The book depends upon a number of incredible concepts, not all of them technical. The book credits "anonymous persons" at the NSA that assisted him. While the usual motive for such secrecy is to defend your security clearance and personality safety, in this case the real motive might be more like that these personnel are unreliable or planting useful missionaria protectiva, to borrow a phrase from the Dune universe.
Premise #1 from the book: a large class of ciphers are uncrackable without massive parallelism (which is what the book posits the NSA but nobody else has)
This premise is true in the sense that 56-bit DES continues to be used and the NSA could crack a preselected message with relatively little effort since it has been done in the outside world using the spare cycles of networks of research machines.
Premise #2: There is a Bergovksy principle used in cryptography circles: this turns out to be true: see Reference to Bergofksy principle on matheplanet
Premise #3: You need to be a genius to create an unbreakable code. That just takes computing power and longer keys. Cracking Enigma depended in part on its users not adhering to its procedures (especially an extra codewheel that would have made it much more difficult if not impossible to crack).
Premise #4: The people who "crack" and give away NSA secrets are driven by deep personal conflicts Fact: The main secrets of the NSA are not technological; they're just the extent of its activities.
Premise #5: Part of create a good code is creating a good key management system. Fact #5: The novel at least teaches us that much.
Criticisms
The factual liberties mentioned above have spawned criticism.
The short-attention-span writing style (128 chapters in 429 pages) of the novel has been noted. Some critics have felt that the characters of the novel are not believable, though others hold that suspension of disbelief makes this irrelevant.
Several examples of deus ex machina are present; some critics argue that this too detracts from authenticity.
Spanish reaction
In Spain, the novel has been criticized for depicting the country as having substandard health care, corrupt security forces and poor telecommunications, among other things. Critics argue that this negative depiction of Spain is far from the truth, arguing that Spain's health service is, according to several criteria, one of the very best in the world; that the country does not suffer from high levels of corruption; and that the Spanish telephone infrastructure and public transport is not as unreliable as Brown suggests. The City Council of Seville, refusing to enter polemics, has invited Brown to visit for a first-hand experience of the city.
The Spanish version of the book was released in February 2006 with the title Fortaleza Digital. It contains a prologue in which Dan Brown claims that Seville is his favourite city in the world and the place where he was inspired to write The Da Vinci Code. Ironically, the polemical and 'dreamy' description of the city helped the book to become a best-seller in Seville during its first month on sale (a similar event occurred in 2005 in Uruguay with the Steven Seagal's film Submerged). [2]
Code solution
The code that appears in the end of the book
128-10-93-85-10-128-98-112-6-6-25-126-39-1-68-78
is decrypted by looking at the first letter of the chapter for each number. For example, chapter 128 starts 'When Susan awoke'. The resulting text is
WECGEWHYAAIORTNU
Decryption is performed using a columnar transposition cipher, termed a "Caesar Square" cipher in the book (this is unrelated to the Caesar cipher). The letters are arranged into a square:
WECG EWHY AAIO RTNU
and read from the top down.
WEAREWATCHINGYOU
Add spaces and you get the plaintext,
"We are watching you"
a reference to the NSA's monitoring systems.
External links
- Digital Fortress page at Mathematical Fiction Alex Kasman's site includes a forum, critique of the math/computing, and his solution to the code.
- (Spanish) Criticism in the Spanish-language Epoca of the book's description of locations in Seville
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