Although espionage in the Civil War era tended to be low on the technical scale, say compared to World War II and our modern era, leaders had to worry about captured or otherwise intercepted correspondence. While telegraph and “wig-wag” communicators often encrypted messages in cypher, to provide a level of security. US Army signal troops used a cipher disk to facilitate such work:
And the Confederates had their own, simpler, version. As with any encryption technique, this added time to the transmission of messages. While fine for daily correspondence, not something a general would want to deal with on a busy battlefield.
Another problem with this disk was security of the cipher itself. Notice the serial number in the reproduction above. These were issued by number and tracked by number to account for each. Not something that every signal operator received. Only those in positions that rated having a cipher.
In the spring of 1864, General P.G.T. Beauregard needed some means to correspond via encrypted messages to subordinates. But some of his subordinates lacked access to the cipher disks, or men with cipher disks. So Beauregard offered his own system:
Hdrs. Dept. of S. Carolina, Georgia, and Florida,
Charleston, S. C., April 7, 1864.
Maj. Gen. Patton Anderson,
General: I inclose you herewith the following simple cipher for future use in important telegrams to these headquarters. For very important telegrams the diplomatic cipher should be used. Please inform me of its reception.
Respectfully, your obedient servant,
G. T. Beauregard,
The inclosed cipher was:
Very simple. Not being a code-breaker myself, I cannot attest to how effective this might be. But I imagine for the intended purpose of encrypting messages sent via telegraph or courier, this would suffice. Not far removed from the “Secret Magic Decoder Ring.”
(Citation from OR, Series I, Volume 35, Part II, Serial 66, pages 406-7.)