| (I) General usage: In mathematics, random means "unpredictable". A
sequence of values is called random if each successive value is
obtained merely by chance and does not depend on the preceding
values of the sequence, and a selected individual value is called
random if each of the values in the total population of
possibilities has equal probability of being selected. [Knuth]
(See: cryptographic key, pseudo-random, random number generator.)
(I) Security usage: In cryptography and other security
applications, random means not only unpredictable, but also
"unguessable". When selecting data values to use for cryptographic
keys, "the requirement is for data that an adversary has a very
low probability of guessing or determining." It is not sufficient
to use data that "only meets traditional statistical tests for
randomness or which is based on limited range sources, such as
clocks. Frequently such random quantities are determinable [i.e.,
guessable] by an adversary searching through an embarrassingly
small space of possibilities." [R1750]
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