Cryptology - Unofficial St. Mary's College of California Web Site

10.9. TRANSPOSITION DURING THE CIVIL WAR 203
conduct secret communications with one another. This was, apparently, “the
first telegraphic cipher used for war purposes” [Plum, page 44].
Later George B. McClellan, a recent railroad executive who became a general
of volunteers, asked Stager to prepare a cipher for use during the campaign
in West Virginia. Stager based this new cipher on his previous one. It was afterwords
adopted as the official cipher of the War Department [Weber]. The cipher
was simply a route cipher. As J.E. O’Brien, a former US Military Telegraph
operator, put it [SSA3, vol 1]
The principle of [this] cipher consisted in writing a message with an equal
number of words in each line then copying the words up and down the
columns by various routes, throwing in an extra word at the end of each
column, and substituting other words for important words and meanings.
The cipher information was printed on cards, about 3 by 5 inches in size.
Printed on the cards were the code words, called arbitrary words, the keys,
called commencement words, and the nulls, called check words or blind
words. The route was also indicated on the card.
Successive editions of the ciphers were aided by the practical experience of
the users, both in Washington and in the field. More code words, more nulls,
and variations on the routes were added. Eventually the cards abandoned and
pamphlets were substituted, in pocket-sized editions, the first with 16 pages,
the last with 48 [SSA3].
The genesis of Stager’s system can perhaps be seen in a simple example that
appears in [Myers]:
The enemy has changed his position during the night. Deserters say
that he is retreating. Smith
We put it into a rectangle in the following given order: down column 1, up
column 4, down column 2 and up column 4, and then add a column of nulls.
Column 1 Column 2 Column 3 Column 4 Column 5
The night. Smith the attacking
enemy Deserters retreating during summer
has say is position unchanged
changed that he his him.
The ciphertext can then be read off:
The night. Smith the attacking enemy Deserters retreating during
summer has say is position unchanged changed that he his him.
Notice the use of significant looking insignificant check words – “attacking” and
“unchanged.”