million billion. Nobody's going to guess that combination by luck, and no one can possibly think of using force and of trying every possible combination one at a time.
How do you decide on the keyword? One way—not the only way—is to have an agreed-on book (one that is changed periodically) and choose a ten-letter combination at random out of it. You then use a small coding machine to code the message around the keyword and send the keyword itself separately. The keyword can be and sometimes is just a scrawled notation such as 73/12 indicating page 73, line 12. Look up the page and line of the book of the week and the first ten letters, or the last ten letters, or whatever you've agreed on is the key.
Either message might, for some reason, not arrive, but it is in the highest degree frustrating if both messages arrive and yet, even taken together, make no sense. Something of that sort happened in January 1968, and it was fatal.
Here are the essential details. A message came through to Saigon headquarters from an operative in Hue. The agent who sent it was the best we had. He was a Vietnamese, heart and soul on our side, and with an excellent command of English that he ordinarily took care to hide. He actually operated with the Vietcong, so you can imagine the risks he ran.
He kept his coding machine well hidden, of course, and the books he used for determining the keyword. They were British paperback thrillers in rotation, and it was his choice. He liked them. They were literate and he ceaselessly polished his English on them. He was proud of his facility with the language—all this turned up afterward, too late—and on those occasions when he met with our men, he would trot out his full vocabulary, and go out of his way to demonstrate his knowledgability on the matter of synonyms, idioms, ambiguities and so on. Our men, being native to the language, didn't know it nearly as well and, I imagine, listened with impatience or, I strongly suspect, didn't listen at all—a terrible mistake.
The key arrived and seemed perfectly clear. Stripped of the red herrings with which it was routinely surrounded, it read "13 THP/2NDL" which was interpreted, quite reasonably, as the thirteenth page and second line. That was turned to in the book, the first ten letters taken, and fed into the computer. The message was then inserted and what came out was garblement, absolute chaos and meaninglessness.
They were astonished, and I imagine they tried it several times before being satisfied that something was wrong. They decided that, through some error, the agent had used the wrong book. They sent a message back to Hue in order to get a confirmation. That meant the loss of time. When they got back nothing, they sent an army officer and I suppose you can imagine what he found.
The agent had disappeared the morning after the message had been sent out. He has never been heard of again as far as I know, so that we can assume the Vietcong finally discovered the game he had been playing. As I said, it was January 1968, and considering what was about to happen, the enemy must have been highly sensitive to all sorts of things.
Well, then, what to do with the message? It didn't work and it wasn't ever going to work. The people at Saigon were quite convinced on that point.
They were therefore faced with two alternatives. The first was simply to ignore it. If a message were intercepted and you never received it, there was nothing to be done, and operationally this fell into the same category. It might just as well never have been received.
However, it was received. The receipt was on record. And if it carried an important communication—as, in point of fact, it did, though no one knew it at the time— someone would have to be blamed, and whoever made the decision to ignore the matter would be the candidate. The people at Saigon had a healthy resistance to the notion of being scapegoated, and looked for a second alternative.
They found one.
How do you decide on the keyword? One way—not the only way—is to have an agreed-on book (one that is changed periodically) and choose a ten-letter combination at random out of it. You then use a small coding machine to code the message around the keyword and send the keyword itself separately. The keyword can be and sometimes is just a scrawled notation such as 73/12 indicating page 73, line 12. Look up the page and line of the book of the week and the first ten letters, or the last ten letters, or whatever you've agreed on is the key.
Either message might, for some reason, not arrive, but it is in the highest degree frustrating if both messages arrive and yet, even taken together, make no sense. Something of that sort happened in January 1968, and it was fatal.
Here are the essential details. A message came through to Saigon headquarters from an operative in Hue. The agent who sent it was the best we had. He was a Vietnamese, heart and soul on our side, and with an excellent command of English that he ordinarily took care to hide. He actually operated with the Vietcong, so you can imagine the risks he ran.
He kept his coding machine well hidden, of course, and the books he used for determining the keyword. They were British paperback thrillers in rotation, and it was his choice. He liked them. They were literate and he ceaselessly polished his English on them. He was proud of his facility with the language—all this turned up afterward, too late—and on those occasions when he met with our men, he would trot out his full vocabulary, and go out of his way to demonstrate his knowledgability on the matter of synonyms, idioms, ambiguities and so on. Our men, being native to the language, didn't know it nearly as well and, I imagine, listened with impatience or, I strongly suspect, didn't listen at all—a terrible mistake.
The key arrived and seemed perfectly clear. Stripped of the red herrings with which it was routinely surrounded, it read "13 THP/2NDL" which was interpreted, quite reasonably, as the thirteenth page and second line. That was turned to in the book, the first ten letters taken, and fed into the computer. The message was then inserted and what came out was garblement, absolute chaos and meaninglessness.
They were astonished, and I imagine they tried it several times before being satisfied that something was wrong. They decided that, through some error, the agent had used the wrong book. They sent a message back to Hue in order to get a confirmation. That meant the loss of time. When they got back nothing, they sent an army officer and I suppose you can imagine what he found.
The agent had disappeared the morning after the message had been sent out. He has never been heard of again as far as I know, so that we can assume the Vietcong finally discovered the game he had been playing. As I said, it was January 1968, and considering what was about to happen, the enemy must have been highly sensitive to all sorts of things.
Well, then, what to do with the message? It didn't work and it wasn't ever going to work. The people at Saigon were quite convinced on that point.
They were therefore faced with two alternatives. The first was simply to ignore it. If a message were intercepted and you never received it, there was nothing to be done, and operationally this fell into the same category. It might just as well never have been received.
However, it was received. The receipt was on record. And if it carried an important communication—as, in point of fact, it did, though no one knew it at the time— someone would have to be blamed, and whoever made the decision to ignore the matter would be the candidate. The people at Saigon had a healthy resistance to the notion of being scapegoated, and looked for a second alternative.
They found one.
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