Choosing The Key
The main strength of a book cipher is the key. The sender and receiver of encoded messages can agree to use any book or other publication available to both of them as the key to their cipher. Someone intercepting the message and attempting to decode it, unless they are a skilled cryptographer (see Security below), must somehow identify the key from a huge number of possibilities available. In the context of espionage, a book cipher has a considerable advantage for an agent in enemy territory. A conventional codebook, if discovered by the local authorities, instantly incriminates the holder as a spy and gives the authorities the chance of deciphering the code and sending false messages impersonating the agent. On the other hand a book, if chosen carefully to fit with the spy's cover story, would seem entirely innocuous. The drawback to a book cipher is that both parties have to possess an identical copy of the key. The book must not be of the sort that would look out of place in the possession of those using it and it must be of a type likely to contain any words required. Thus, for example, a spy wishing to send information about troop movements and numbers of armaments would be unlikely to find a cookery book or a romantic novel useful keys.
Read more about this topic: Book Cipher
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Famous quotes containing the words choosing the, key and/or choosing:
“Constantly choosing the lesser of two evils is still choosing evil.”
—Jerry Garcia (19421995)
“I cannot tell what I am as much afraid of, as a woman who invariably washes on Monday. It is a kind of key to character; and if her mouth is not puckered and her brow wrinkled, they will be, unless she repents.”
—Jane Grey Swisshelm (18151884)
“Although Ive risen! and my back is bold.
My tongue is brainy, choosing from among
Care, rage, surprise, despair, and choosing care.
Im semi-splendid within what Ive defended.”
—Gwendolyn Brooks (b. 1917)