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Posted By: Dave Gaddy on: 04/19/2010 21:55:50 EDT
Subject: RE: Breaking the SC code

Message Detail:
Tom,
From the standpoint of the cryptanalyst (="codebreaker"), Morse code (whether American or International) and the Myer visual system for flags and torches are monoalphabetical (simple substitution) ciphers. They yield to the same sort of letter-frequency analysis that Poe featured in "The Gold Bug." Thus when we refer to, say, Morse as "code" we are not using the word in the same sense as the crypt specialist. We are using the word "code" to describe a system, much as "the legal code," "the building code," etc.

The Myer-Alexander system involved both the use of gestures or movements of flag or torch AND the alphabetical letters and numerals those movements equated to. THEY DID NOT use the same code. (Repeat NOT.) (Alexander reversed the left-right motions and "scrambled" the alphabetical and numerical equivalencies that Myer originated pre-war. (I assume Myer also changed at wartime, knowing of Alexander's mastery.) Little thought seems to have been given to enemy interception and exploitation of the traffic.

It seems to have taken close to a year for the two sides to grasp what I just wrote. Prior to that time, the "alphabet" was changed upon evidence of compromise, and both sides quickly lost the letter frequency basis that Myer had originally used (assigning simplest motions to highest frequeny letters). After doing that a few times, both resorted to cryptography for secrecy. Myer introduced his cipher disk around mid-1863 as an "on-line" cipher -- one that could even be changed while sending. The Confeds took the off-line approach. Sensitive messages were enciphered with the Vigenere cipher and then sent using the current version of the signal "code," not particularly caring if the scrambled cipher text could be read, for the security of the underlying cipher was trusted.

Now, to all of the above, introduce the human factor: all of this required dedicated and careful users. It all took extra time and effort. There was little or no monitoring for compliance with the rules and regs, except that imposed on the scene by the signal officer in charge. Human nature being what it is, the easier way, the looser practice, rationalization, often prevailed. (Despite recorded statements to the contrary about "all important messages being sent in cipher [i.e., with the disk]" by Union signalmen, Confederate interceptions claim that they were usually "reading everything." It was the old story -- each side bragging of their prowess against the enemy, each side confident of their own security. (Examples up to the final weeks in Virginia.)

From the standpoint of contemporary usage, when you see refs to learning or reading (or breaking) the enemy's "signal alphabet," read that as the ability to comprehend the underlying plain text (which would imply that the basic "code" had been broken). That would have involved at least the bulk of the alphabet -- numerals didn't lend themselves to frequency analysis and were slower to recover. (A good example in Union analysis dates from Dec 1862 Fredericksburg.)

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