4
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4.1
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. . , , 1 (, ), , 2 (). . .
: (. 4.1)
1 ;
2 ;
1() 1;
D 2() - 2;
. 4.1
, 2 . 1, 2 .
:
1 ³ 1 .
2
1 : →
D 2: →
.
2.
. . , , :
1 1 2 , .
2 ³, 1 ,
= 1 ()
3 , 2 ,
= D 2 () = D 2 ( 1 ())
4 , 1 2 , .
5 , 1 , .
4.2
. . Y .
f: → Y
,
y = f (), y Y.
y Y , , f () = y ( , ).
f Y→ .
. P Q,
N = P * Q
.
N = P * Q ( P Q) , N.
. N , , 1≤< N.
ZN:
ZN = {0, 1, 2, , N - 1}.
N
f , N: ZN → ZN,
f, N () = (mod N),
, 1 ≤ ≤ N 1.
, f, N ().
y = , = logA (y). f, N () , .
, N y , ,
(mod N) = y.
, . .
, , . , , , ( , , ). , RSA.
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4.3 RSA
RSA, 1978 . Rivest, Shamir Aldeman, 1977 . RSA , , .
.
RSA 1, 2,
ZN = {0, 1, 2, , N - 1},
N :
N = P * Q.
P Q . P Q .
ZN N N.
³ 1 , :
1 < 1 ≤ φ(N); (1, φ(N)) = 1; φ(N) = (P - 1) (Q - 1),
φ(N) , 1 N, N.
, .
, , 2 , ,
1* 2 ≡ 1(mod φ(N))
1 = 2 -1 ( mod (P-1) (Q -1)).
, P Q φ(N).
³ 1 , 2 .
:
= 1 () = 1 (mod N).
( ) :
= D 2 () = 2 (mod N).
, , RSA. , - . , . .
RSA.
( ).
1 = 3 Q = 11.
2 N = 3 * 11 = 33.
3
φ(N) = φ(33) = ( - 1)(Q - 1) = 2 * 10 = 20.
³ 1 , :
1 < 1 ≤ 20; (1, 20) = 1.
, 1= 7.
4 2 ,
1* 2 ≡ 1(mod φ(N))
2 ≡ 7-1(mod 20) = 3.
5 (N = 33, 1= 7).
6 : 1, 2, 3. 312( 011.001.010),
1 = 3, 2 = 1, 3 = 2.
7 1= 7 N =33 , :
i = i 1 (mod N) = i 7 (mod 33)
1 = (37) (mod 33) = 2187 (mod 33) = 9,
2 = (17) (mod 33) = 1 (mod 33) = 1,
3 = (27) (mod 33) = 128 (mod 33) = 29.
1, 2, 3 = 9, 1, 29.
8 (9, 1, 29) 2= 3:
i = i 2 (mod N) = i 3 (mod 33)
1 = (93) (mod 33) = 729 (mod 33) = 3,
2 = (13) (mod 33) = 1 (mod 33) = 1,
3 = (293) (mod 33) = 24389 (mod 33) = 2.
, .
RSA , , 4-5 .
RSA , . RSA 1000 DES. RSA 100 DES. , 䳿 .
4.4
, .
.
( , ), P G, G < . P G .
X, < . .
Y
Y = GX mod P.
, , , 1< K< (P -1), , K (P -1) .
:
a = GK mod P,
b = YKM mod P.
(a,b) . .
, (a,b),
= b/ aX (mod P),
aX ≡ GKX mod P,
b / aX (mod P) ≡ YKM / aX (mod P) ≡ GKX M / GKX (mod P)≡ M(mod P).
. = 5 .
=11, G = 2, = 8.
Y
Y = G mod P = 28 mod 11 = 256 mod 11 = 3
, Y = 3.
= 9.
, (, -1) =1. ij, (9, 10) =1.
a b:
a = GK mod P = 29 mod 11 = 512 mod 11 = 6,
b = YKM mod P = 39*5 mod 11 = 19683*5 mod 11 = 98415mod 11 = 9
(6, 9) .
. , = 8:
= b/ aX (mod P) = 9/68 mod 11 = 9/1679616 mod 11 = 5,
1679616* ≡ 9 mod 11.
: = 5.
4.5 .
, - .
. , :
, ;
, .
䳿 .
, , .
, . .
, , , .
, , :
1. (, ) Ks.
2. Ks.
3. Ks K K.
4. Ks, .
ij .
5. Ks K K .
6. Ks .
, Ks .
, . , - .
4.1 , .
4.1 - , .
,
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