Dan Brown - Digital Fortress book
Andre Amorim decouk at gmail.com
Wed Jan 14 17:12:07 CET 2009
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>concept of rotating-cleartext ever existed.[1]
>Charly Avital
Thanks Charly Avital for explanations.
I know, I'd had read his others books firstly... and yes... I read
like Dan as who is reading comics books, no worrys.
The thing that really catch my attention was the concept of
rotating-cleartext thing.
But I think the book is good in the sense that it's encourage those
who are not expert in the subject to know more about. Thats why I'm
here asking.
[s]
-AA
2009/1/14 Charly Avital <shavital at mac.com>:
> Andre Amorim wrote the following on 1/14/09 9:49 AM:
>> Hi all,
>>
>> Anyone knows what's is fact (real) and what is fiction in Dan Brown
>> novel, Digital Fortress ?
>>
>> Kind Regards,
>> [s]
>
>
> I read it years ago. I believe it's the worst book ever written by Dan
> Brown.
>
> Some excerpts from: <http://en.wikipedia.org/wiki/Digital_Fortress>. I
> believe the following list of Mr. Brown's errors (or delusions) is not
> exclusive, to say the least.
>
> Still, it's my opinion, only.
>
> Charly
>
> ----------
> "Although the book's website cites reviews lauding Digital Fortress for
> being extremely realistic, the book contains a number of technical
> errors and misunderstandings in computers, math and technology.
>
> * Brown mentions a Hungarian mathematician, Josef Harne, who in 1987
> proposed an encryption algorithm that, in addition to encrypting,
> shifted decrypted cleartext over a time variant. However, neither Harne
> nor the concept of rotating-cleartext ever existed.[1]
> * Brown says the atomic bomb dropped on Nagasaki was fueled by the
> uranium isotope U-238. The Fat Man bomb dropped on Nagasaki was fueled
> by plutonium 239, and U-238 is not an easily fissionable isotope of
> uranium (needing a fusion reaction to initiate fission in the U-238).
> * Brown also inaccurately portrays the leadership of the NSA. As
> part of the Department of Defense, the NSA director - by law - must be a
> three-star Lieutenant General or Vice Admiral.
> * Brown confuses bits with bytes, describing a 64bit string as
> containing 64 alphanumeric characters. In fact it would be just 8
> assuming the most basic 8bit character encoding, each character being a
> byte or 8 bits.
> * Brown suggests that TRANSLTR, a machine capable of breaking a
> 64bit key in 10 minutes would take just an hour to break a 10,000 bit
> key. This is a gross misunderstanding of the relationship between key
> lengths and the time required to brute force them. Such a machine would
> take over 80,000 years to break a 96-bit key and over 350,000 billion
> years (nearly 30,000 times the current age of the universe) to break a
> 128-bit key. The number of years it would take to break a 10,000 bit key
> isn't even practical to write down - it has 2,987 digits.
> * Brown repeatedly confuses storage or processing of data with
> execution. For example, TRANSLTR is threatened because it has tried to
> crack Digital Fortress, which is actually a virus, and the database is
> similarly threatened because Digital Fortress is sent to it by TRANSLTR.
> Databases and password crackers do not execute the information presented
> to them, so it wouldn't matter that Digital Fortress contains harmful
> instructions.
> * Characters who are supposedly experts in cryptography seem to
> think there is no such thing as an unbreakable encryption scheme. See
> one-time pad."
> ----------
>
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For the method I'll be using here, the cleartext should be a square number of letters. For example, one flew over the cuckoo's nest
To prevent the cipher from being too easy to crack, you need to change the cleartext in a reversible manner. My method, rotating it, involves writing the cleartext in columns and then reading it in a spiral. Once done, you can add a random letter at every prime numbered space, or some other pattern that's easy to remember and hard to crack.
In this example I started from the middle of the left side, and reversed direction for the second loop of the spiral
Choose keyword
The most important thing to remember is that the keyword is the security of your message. if you choose one that's too short, it can be cracked extremely easily. However, if you choose one that's too long relative to the cleartext, it can get dicey. Usually a keyword of 6-10 letters is decent. For the sake of the demonstration I'll use abcdefghi as the keyword
Rotating Cleartext
Flaw 1: the rotating cleartext algorithm. There is no such thing. There is an addition to the Vigenère cipher which is called "autokey" and uses the cleartext to expand the key instead of repeating the key. As soon as the key is exhausted it appends the cleartext. But it's breakable too.
If you haven't shared the cleartext in advance, you can tack it on the end of the coded message, but for that you have to hide it. you could do the same thing you did with the cleartext in step 2. Give to a friend who knows the protocol and you're finished
