, , , . . , , . . , .
, , . [9] ( ) RSA, . , 64- 512- RSA, 128- RSA 2300 .
-
2.4 , . , . , , , , . - ( . hash function) , . - 2 :
- - ;
- - .
-
- . - H(x), :
1) ;
2) H(x) ;
3) H(x) ;
4) x x x, H(x)=H(x).
x x: H(x)=H(x) -.
- H(x), 1) 3) - :
5) x x,
H(x)=H(x).
- , . - 1. x, x x , H(x)=H(x). , - , H(x) N, N / 2. - , : 0,63 N .
|
|
-, . E(m,k) m k, v0 . M m1, , mt . H(m) :
h0 = v0, | |
h i = E(h i-1,mi), i = 1t, | (2.24) |
H(m) = h t. |
E(m,k) DES, - - , . , , :
h 0 = v0, | |
h i = E(h i-1,mi)h i-1,i=1t, | (2.25) |
H(m) = h t. | |
- | |
, SHA-1. |
SHA-1
SHA (Secure Hash Algorithm) SHS (Secure Hash Standard), 1993 . , . SHA-1, .
264 , SHA-1 160- (). M , 512 . : - 1, , - , 64 , 512, 64- . , 800 , 801- =1, 960 , 64- 800, 1024- . 2.18. 32- :
A =0x67452301; B =0xEFCDAB89; C =0x98BADCFE; D =0x10325476; E =0xC3D2E1F0.
a0, b0, c0, d0, e0. 512 80 . ft:
ft(X,Y,Z)=(X Y) ((X) Z) t =019;
ft(X,Y,Z)=X Y Z t =2039 t =6079;
ft(X,Y,Z)=(X Y) (X Z) (Y Z) t =4059.
2.18 - SHA-1
:
Kt =0x5A827999 t =019;
Kt =0x6ED9EBA1 t =2039;
Kt =0x8F1BBCDC t =4059;
Kt =0xCA62C1D6 t =6079.
M 16- 32- M0, , M15, Wt: | |
Wt = Mt | t =015; |
Wt =(Wt-3Wt-8Wt-14Wt-16)<<<1 | t =1679. |
<<< X X , + 232.
|
|
512- , a, b, c, d, e A, B, C, D, E , ( a, b, c, d, e , ).
, 160- .
-
- H(k,x) :
- x H(k,x) ;
- ;
- k x H(k,x);
- x
H(k,x), k;
- k, {x, H(k,x)} H(k,x) x x.
(. Message Authentication Code,.MAC).
( ).
- - .
H(x) - . , - H(k,x). :
H(k,x) = H(k|x),
H(k,x) = H(x|k), (2.28) H(k,x) = H(k1|x|k2), k=k1|k2.
| (2.28) , .
- DES. m m1,,mt 64 , - (k ):
c0=0,
ci=DESk(mi ci-1), i=1,,t, H(k,m)= ct