Monday, December 27, 2010

Explanation of Civil War Message, Decoded 147 Years Later

In the news today, I read about a Civil War message that was found in a bottle and decoded just recently. However the news article wasn't very clear on the how the message was encoded.
With a little trial and error, I too was able to decode the message. The message uses a Vigenère cipher and a key of length 15. After struggling with some transcription and encoding errors in the message, I was able to determine what was the intended coded message:
SEAN WIEUIIUZH DTG CNP LBHXGK OZ BJQB FEQT XZBW JJOY TK FHR TPZWK PVU RYSQ VOUPZXGG OEPH CK UASFKIPW PLVO JIZ HMN NVAEUD XYF DURJ BOVPA SF MLV FYYRDE LVPL MFYSIN XY FQEO NPK M OBPC FYXJFHOHT AS ETOV B OCAJDSVQU M ZTZV TPHY DAU FQTI UTTJ J DOGOAIA FLWHTXTI QLTR SEA LVLFLXFO.
If you repeatedly write the key phrase "Manchester Bluff" above the letters it tells you the offset from the actual letter. A is an offset of zero (the same letter in the plain text). B is an offset of 1, C is 2, etc. The decoded message is:
Gen'l Pemberton, You can expect no help from this side of the river. Let Gen'l Johnston know, if possible, when you can attack the same point on the enemy's line. Inform me also and I will endeavour to make a diversion. I have sent you some caps. I subjoin despatch from Gen Johnston.
After I figured out the key phrase I noticed in the Wikipedia article that the Confederate leadership primarily relied upon three key phrases, "Manchester Bluff", "Complete Victory" and, as the war came to a close, "Come Retribution".

2 comments:

  1. That story has seemed to arouse some interest.
    Did you use the Vigenère cipher generator on the "Dead Confederates" site?

    I suppose the (Minié ball?) was present to sink the vial in case the message had to be ditched.

    The message I would like to see the solution of is T.J. Beales Msg 1. Although, I can see why the initial solver who found the treasure would say nothing.

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  2. I did it by hand using a spreadsheet to deduce the key. It wasn't until afterward that I found out that "Manchester Bluff" was used for quite a few Confederate messages.

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