History PhD Student Reaches out to Cryptographers to Help Break a Civil War Code

http://diarycodebreak.wordpress.com/

by justine • 14 years ago

115 20 14 years ago

diarycodebreak.wordpress.com

lignuist3• 14 years ago

Since he was using very uncommon symbols and the cipher is old, it's not so unlikely, that the author used a simple letter replacement table. Something like:

a -> #,

b -> *,

c -> =,

...

and so on. Unfortunately the handwriting is a bit messy and hard to read, but I'd try to make a frequency table for every symbol and compare that to a frequency table of letters in the english language:

http://en.wikipedia.org/wiki/Letter_frequency

Now try to replace the most frequent symbol with e, the second most frequent symbol with a or t and so on. Try some variations and look, if it makes any sense.

Locke1689• 14 years ago

If those pictures are the only coded messages letter frequency may not have enough ciphertext to run on reliably.

lignuist3• 14 years ago

True, but that's why I'd try some variations.

betawolf334• 14 years ago

A simple substitution cipher is of course a good guess, but I suspect a homophonic one is more likely if the author knew anything about cryptography and thought it might come under attack. It's simple enough to come up with a number of homophones to complicate frequency analysis.

lignuist3• 14 years ago

> I suspect a homophonic one is more likely if the author knew anything about cryptography

How likely is it, that he had a deeper knowledge of cryptography in the 1860ies? But of course, if he had, it's still likely, that he used something more sophisticated.

http://en.wikipedia.org/wiki/History_of_cryptography#Cryptog...

Given the fact, that "12345" is still a common password in 2012, I would at least give it a shot. ;)

larrydag2• 14 years ago

Intresting thought. You could also use the number frequency of letters found in the rest of the journal passages that are not cryptic. That perhaps may be a better indicator for the symbols as it's the writers own tendencies.

indubitably• 14 years ago

It's astonishing to me how little understanding people have of Unicode.

stickfigure• 14 years ago

It will take a major feat of cryptanalysis just to decipher the guy's handwriting, let alone the code parts.

Thanks for reminding me why I work with computers.

freeak• 14 years ago

Is this what is needed?:

1. Assign ascii to the symbols in the code

2. Transcribe the code to ascii

3. Solve the code in ascii using techniques from Snyder and Barzilay

deserted2• 14 years ago

Yes.

madao• 14 years ago

perhaps its a form of shorthand

http://upload.wikimedia.org/wikipedia/commons/thumb/e/ef/Ecl...

deserted2• 14 years ago

Forwarded to a cryptography Professor and some of his students : )

efsavage• 14 years ago

I've somehow been conditioned to think of these Civil War diaries and letters as full of flowery prose and beautiful handwriting. It's actually amazing to me to see someone writing plainly and with handwriting almost as bad as my own.

jerfelix2• 14 years ago

Here's the first four images... ready for parsing by your program:

:::: image 1, left:

s-tac-toe equals minus-dot seven ex comma slash-slash-backslash gamma capital-l lower-j ex slash

:::: image 1, right, downward

capital-t capital-i equals four parallel-lines slash-slash-backslash equals-slash comma s-tac-toe slash-slash-backslash slash-slash-backslash-backslash comma

:::: image 1, left, upper

capital-l divided-by capital-i comma equivalent comma lower-j comma capital-f slash-slash-backslash capital-i squared-capital-n zee slash-slash-backslash-backslash comma divided-by slash-slash comma slash-backslash-backslash slash-slash minus-dot slash-slash-backslash

:::: image 2

plus-dot plus leaning-heart upsidedown-t minus vertical-line ex comma

leaning-heart capital-m capital-i capital-a minus three-peaks comma vertical-line crap capital-b close-bracket plus script-j script-s lower-d comma

u-bar three-peaks capital-i

:::: image 3

capital-l backslash divided-by c-slash-slash capital-i comma capital-i equivalent divided-by slash-slash-backslash-backslash comma capital-i minus-dot three-horizontal-two-vertical ex comma equals zee capital-l

l-in-l 11-over-1 comma y-slash-slash slash-slash-backslash-backslash comma capital-i divided-by comma minus-lower-dot c-omega slash-slash slash-i 11-over-1 slash-slash square-c equals capital-l equivalent slash-slash comma

capital-l slash-slash slash comma l-on-l plus slash-backslash-backslash slash-slash-backslash-backslash comma 1-slash-1 11-over-1 capital-z comma capital-i equals ex comma j divided-by c-slash-slash slash-slash capital-l divided-by slash-slash ex comma

:::: image 4 (repeats image 2)

plus-dot plus leaning-heart upsidedown-t minus vertical-line ex comma

leaning-heart capital-m capital-i capital-a minus three-peaks comma vertical-line crap capital-b close-bracket plus script-j script-s lower-d comma

u-bar three-peaks capital-i

jerfelix2• 14 years ago

Here's a frequency chart of the first 3 images:

(23, 'comma') (10, 'capital-i') (8, 'slash-slash') (7, 'divided-by') (7, 'capital-l') (6, 'ex') (5, 'slash-slash-backslash-backslash') (5, 'slash-slash-backslash') (5, 'equals') (3, 'plus') (3, 'minus-dot') (3, 'equivalent') (3, '11-over-1') (2, 'zee') (2, 'vertical-line') (2, 'three-peaks') (2, 'slash-backslash-backslash') (2, 'slash') (2, 's-tac-toe') (2, 'minus') (2, 'lower-j') (2, 'leaning-heart') (2, 'c-slash-slash') (1, 'y-slash-slash') (1, 'upsidedown-t') (1, 'u-bar') (1, 'three-horizontal-two-vertical') (1, 'squared-capital-n') (1, 'square-c') (1, 'slash-i') (1, 'seven') (1, 'script-s') (1, 'script-j') (1, 'plus-dot') (1, 'parallel-lines') (1, 'minus-lower-dot') (1, 'lower-d') (1, 'l-on-l') (1, 'l-in-l') (1, 'j') (1, 'gamma') (1, 'four') (1, 'equals-slash') (1, 'crap') (1, 'close-bracket') (1, 'capital-z') (1, 'capital-t') (1, 'capital-m') (1, 'capital-f') (1, 'capital-b') (1, 'capital-a') (1, 'c-omega') (1, 'backslash') (1, '1-slash-1')

larrydag2• 14 years ago

There are definitely more symbols then there are letters in the alphabet. So that could mean he has multiple ciphers or that some symbols are substitutes for words, possibly common phrases.

betawolf334• 14 years ago

I did some very rough frequency analysis using this last night, but didn't get very much from it.

The comma symbol is more frequent than any letter usually is in English, but given the small corpus that's not too telling. It could stand for an 'e', or the coded text could be lists and they're just commas.

Someone commented on the article that he suspects the 'divided by' symbol might stand for 'i' due to its placement, which agrees roughly with the position it gets in the frequency table. Someone else has suggested that the language being masked might not be english, which is an intriguing possibility.

The frequencies aren't flat, which seems to suggest it's either not a very good homophonic cipher (he just threw some odd replacments and codeword-symbols in there, basically still a substitution cipher) or it's a very good one (he consciously aimed at misleading symbol frequencies).

The rough nature of the writing (also discussed on the article) suggests that the code was probably memorised, and thus not the result of a very laborous method.

History PhD Student Reaches out to Cryptographers to Help Break a Civil War Code

Related Stories