TheCodeBreakers
mechanical apparatus may be necessary," and not "the key proper."
Kerckhoffs here makes for the first time the distinction, now basic to
cryptology, between the general system and the specific key. Why must
the general system "not require secrecy," as, for example, a codebook
requires it? Why must it be "a process that. . . our neighbors can even
copy and adopt"? Because, Kerckhoffs said, "it is not necessary to
conjure up imaginary phantoms and to suspect the incorruptibility of
employees or subalterns to understand that, if a system requiring
secrecy were in the hands of too large a number of individuals, it could
be compromised at each engagement in which one or another of them
took part." This has proved to be true, and Kerckhoffs' second
requirement has become widely accepted under a form that is sometimes
called the fundamental assumption of military cryptography: that the
enemy knows the general system. But he must still be unable to solve
annaabi.ee 
