Enemy Code Broken 137 Years Late

Random Hall writes "Dr. Kent Boklan, a former NSA employee and current Director of Security Research for Razorpoint Security Technologies, has described how he recently deciphered a message encrypted by Confederate Army General Edmund Kirby Smith on 14 September 1862."

Details...

[damaged]

First off, why the hell is this under IT?!?

It would have been nice if the write-up gave a little more detail. It was encrypted using a Vigenere cipher [wikipedia.org] with a key of "BALTIMORE".

For those too lazy to read the article, here's what the message said:

The enemy rapidly concentrating at Louisville and Covington. They are confident of soon crushing my force here it is important out communication with each other should be kept open I shall present a bold front in order to deceive the enemy as long as possible and when compelled I shall fall back upon you. Marshall is still far behind. E.K.S.

Re:It's true what they say...

[kestasjk]

RTFA; the author didn't allow himself to use any methods which weren't available at the time. He didn't use computers, and this message could have been broken in the same way and in the same amount of time as when it was written.

To summarise it was a known plaintext attack. His signature was EKS, and he signed his signature encrypted. The author worked back from there.

Re:Details...

[Vlad_the_Inhaler]

Napoleon's armies used a far better encryption scheme 60 years earlier.

Their system was numbers up to (I think) 1000,

• some of those numbers represented letters, numbers, special characters; several different numbers would map to a single character
• some mapped to names, places, words
• some mapped to nothing at all. They were simply there to confuse the issue.

Sometimes messages were a mixture of clear text and code. One of them (which was meant to be intercepted) ran something like: I am confident of repulsing the enemy's attack if I receive major reinforcements. Obviously only the second part was in code.

The code was eventually cracked in the Peninsula campaign (Spain) by Wellington's army, partially through brilliance on the part of the crackers and partially through mistakes by the French. Some of these mistakes were:

• the code was extended by 200(?) numbers. All of these extras were names, words or places relevant to the Peninsula campaign. The fact that these extras were in a block rather than spread around weakened the code.
• Some of the mixed code/cleartext messages were very poorly thought out
• the sheer volume of intercepted messages. The French were hated and the Guerillas intercepted a *lot* of their communications.
• the French kept to one code sheet far too long

At some late stage in the campaign, an actual codesheet was captured. This was actually bad because the French were forced to adopt a new one, but by then the outcome of the campaign was no longer in doubt.