Can you decipher the word UTEM?

Cryptogram in a message in a bottle

This note, dated July 4th, was found in a bottle near the city of Vicksburg, USA, and is believed to have originated during the American Civil War. The bottle and note are in the Museum of the Confederacy in Richmond. Since the Vigenère encryption was used in the Army of the Southern States at that time, this cryptogram is probably also one of these in this cryptogram. It is known that only four different keywords were used at the time:


The first two words of the cryptogram are probably "SEAN WIEUIIUZN" and you will first decrypt them with each of these key words. So one gets in turn


The keyword "MANCHESTERBLUFF" was used, which means that decryption would be a routine, especially since the spaces between the words were retained. However, the ciphertext letters cannot always be clearly identified, as the last letter of the second word shows. So one can read in the relevant history books that Lieutenant General John Clifford Pemberton (1814 - 1881) defended the city of Vicksburg with an army of the southern states in the summer of 1863, but finally had to surrender to the Union army. The last plaintext letter of this word is therefore an "N", which requires an "H" at this point for the keyword used in the ciphertext. You can now identify this with a little good will.

The parallel passage "SEA" at the beginning and in the last line is also noticeable. If you decipher the last line "SEA LVLFLXFO" also with the key "MANCHESTERBLUFF", you get "GEN JOHNSTON" and find in the history books the information that General Joseph Eggleston Johnston (1807-1891) was one of the highest-ranking generals in the Southern Army and at the time of the Battle of Vicksburg was also Commander-in-Chief of the Mississippi Army led by General Pemberton.

But before the rest of the cryptogram is decrypted, a curiosity should be examined more closely. Towards the end of the first line, the word "FEQT" appears twice in direct succession, which is extremely unlikely for Vigenère encryption with a keyword of length 15. If you try all 15 shifts of the keyword MANCHESTERBLUFF for the sequence "FEQTFEQT", you get


So the decryption of "FEQT" is simply "FROM" and the "ANCH" part of the keyword was used for this. While writing, this word was probably accidentally doubled and can be deleted from the cryptogram. In particular, the following word "XZBW" can be deciphered using the next four letters "ESTE" of the keyword and results in the plain text "THIS".

The following situation arises for the first line of the cryptogram, the letters of the ciphertext that have not yet been identified being indicated by the placeholder "X" and the missing plaintext letters by "?".

GENLPEMBERTON ?????????????????? FROMTHIS ????

In particular, exactly 18 letters are missing in the gap. If you count this back from "FEQT", you notice that the illegible three characters after "WIEUIIUZH" have actually been deleted and must therefore be ignored during decryption.

Now you can try to decipher this missing sequence of 18 letters, using exactly the sequence "FFMANCHESTERBLUFFM" as the key. You might start with the six-letter word "LBNX? K", which is relatively easy to decipher except for the penultimate letter. If you read an "O" for this, you get with the relevant part "HESTER" of the key "EXVEKT", which can best be interpreted as "EXPECT". Then the ciphertext would have to be "LBHXGK" at this point, which is plausible for the penultimate letter "G" (instead of "O") and for the third letter "H" by comparing it with the last bold letter ("H") of the second word now also seems reasonable.

The three-letter word immediately in front of it could now be read as "CHP" or as "CNP". It would have to be decrypted with "ANC" and therefore "CUN" or "CAN", whereby only the second option is useful. The beginning of the plaintext would then be "GENL PEMBERTON ___ CAN EXPECT", which suggests the missing three-letter word "YOU". If you encrypt this with "FFM", you get "DTG", which you can understand by comparing the letters "G" in this and the fifth word.

The key for the last four-letter word in this gap is "UFFM" and the middle ciphertext letters "JQ" are safe to read. The first and last letters may be "E" or "B". In fact, "BJQB" provides the meaningful plaintext word "HELP". This would be the previous plain text in the first line


The last word of the line, apparently "JJOA", but with the associated key "RBLU", delivers "SIDG", which does not make a meaningful word. However, "SIDE" would match the previous plain text and the associated ciphertext would be "JJOY". Since the "Y" is written completely differently in all other places, an encryption error could have occurred at this point. In any case, the probable plaintext results for the first line

Genl. Pemberton, you can expect no help from this side

The next three words "TK FHR TPZWK" can be deciphered with "FFMANCHEST" rather effortlessly to "OF THE RIVER", which is a meaningful continuation of the previous plaintext. Apparently the message was put in a bottle and was to be thrown into the river in the hope that it would be found on the other side by someone who would forward its contents to the Southern Army.

It is just as difficult to reconstruct the complete plain text despite some encryption errors and difficult-to-read letters:

Genl. Pemberton, you can expect no help from this side
of the river. Let Genl. Johnston know if possible when
you can attack the same point of the enemy's line.
Inform me also and I will endeavor to make a diversion.
I have sent you some caps. I subjoin despatch from
Gen. Johnston

Author: Udo Hebisch
Date: 02/24/2017