I was researching the US military's DIANA one-time-pad system and came across the following quote purportedly from a former US Special Forces soldier:
Special Forces were one of (if not the only) units in Vietnam to utilize Morse code on a regular basis. We used a method of encryption called the Diana Cryptosystem.
The basis of these one-time pads, is that there were only two matching pads in existence, and they would only be used one time. They were booklets that contained randomly generated groups of 5-letter words, 30 words to a page. The person sending a message would first write the letters to the message, over these random groups of words. Included in the front of each one-time pad was a one-page encryption table. If I wanted to send the letter P, and the letter under the P was an A, then I would send a K. The person listening on the frequency at the other end, would have the other matching pad. They would write the letter they received (a K) over the letter in their one-time pad (an A), and decipher it based on the table, yielding the original letter P.
Wouldn't the use of random words as reported by the soldier rather than groups of random letters diminish the security of the system, as the letters in 5 letter English words are not randomly positioned?
I am aware that "secure" in this context--messages between Special Forces camps during wartime--may just mean keeping messages secure long enough that they are no longer useful even if broken.