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, . () F (X) (Y): F: X ↔ Y. X Y: X = { x 1, x 2, xn }, Y = { y 1, y 2, yn }. F p n = | X | = | Y |: xi y p( i ) . , . p(i) , i.
. , : , ( , 'z' 'a'). , "secret" "vhfuhw". (. . 2.3). , .
a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z |
d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z | a | b | c |
. 2.3. . |
. 0 25: a = 0, b = 1, , z = 25. : i i +3 (mod 26), "mod 26" 26.
, , i i + k (mod 26). k.
, . n { a 1, a 2, , an } , ai aj, j = k ⋅ i + l (mod n). n k , (n, k) = 1.
, . . , , . , '', , , '' (, '' '' ), '', '', '' .. : 'E', 'T', 'A', 'I', 'N'. , , , .
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, , . {p1, p2,, p m } - Y (k, i), p i. i - Y (k, i), k .
. . m : k = (k 1, k 2, , km). t = (t1, t2, ) c = (c1, c2, ) : c 1 = t 1 + k 1 (mod 26),
c 2 = t 2 + k 2 (mod 26), .. m k, (m +1)- k 1, .. , , : k 1, k 2,, km, k 1, k 2,, km, k 1, k 2,
, , . m ( ), , ti, tm+i, t 2 m+i, "" ki (i =1, , m).
(.. m), . , . . , .
, . , . , . .
. , . fi i (i ). ti (.. , ) Fi, fi (.. , ), Fi Fj . ti Fi. , , .
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n: , , (XOR): .
: , ( XOR ).
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1) ;
2) ;
3) () , .
, . , .
, . (). .
: gi = a × gi 1 + b (mod m), gi i - ; a, b, m g 0 . 0 m 1, gi gj , : gi +1 = gj +1, gi +2 = gj +2, .. { gi } , m. , , ( m), :
b m ;
a 1 m;
a 1 4, m 4.
:
, i = 0,1,
Å 2, j - , , , .
. .. , n .
. ().
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. 2.4.
. 2.4. . |
. . n , n - . , , 1 . . . .
XOR , 1. .
n - 2 n 1 . , 2 n 1 . ( 2 n 1, , , , .) 2 n 1 , . .
, n - 2 n 1, f (x) = hnxn + hn 1 xn 1 + + h 1 x + 1, 1, . f (x) n , ( ) , x n, f (x).
. , . - , . , .
f (x) = x 4 + x +1. . 2.5 .
[0, 0, 0, 0], . . 2.1 a 0, a 1, a 2, a 3, t [0, 1, 1, 0].
. 2.5. f (x) = x 4 + x +1. |
2.1
16- f (x) = x 4 + x +1
t | a 0 | a 1 | a 2 | a 3 | t | a 0 | a 1 | a 2 | a 3 | |
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0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 0, 1, ¼ 241= 15.
. , , , , , .