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random and unpredictability
random:
uniform distribution 平均分配
independence
unpredictability:
sequence of numbers that appear to be random are generated by some algorithm
Random number
physical noise generator:random and precision
published random numbers:predictable
psedorandom numbers :deterministic not statistically random
psedorandom number:
Xn+1=(aX(n)+c)mod m
m=2^31
three criteria for random number generate
full-period :全部的值都出現過
appear random :generated sequence 是random的
efficiently :implement with 32-bit arithmetic
cyclic encryption:
master key is deduced by several session keys based on earlier keys
ANSI X9.17
one of the strongest psedorandom number generators
Input1:64-bit of data and time
Input2:64-bit of seed value
Keys :K1 and K2 56-bit DES key used for 3 Trible-DES encryption modules
Output:64-bit psedorandom number and 64-bit seed value
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