- , . , F IV. - . -, (Message Authentication Code).
- , , - - , - - . - . , - .
64-, , - , .
, - , . , - , .3. :
0 = I, i = A() Å ,Å - 2 ( ); I - ; , , i, i-1, (i Å i-1) .
.3. -
i , .
, , , 64 . 52 , . 12 , - .1.
1 | ||||||||||||||||||||||||||
|
, , .4.
.4.
-, , . , - . , (, ). , .
|
|
MD5
MD5 (Message Digest 5) . MD5 4 32- U, V W:
f(U,V,W)=(U AND V) OR ((NOT U) AND W) g(U,V,W)=(U AND W) OR (V AND (NOT W)) h(U,V,W)=U XOR V XOR W k(U,V,W)=V XOR (U OR (NOT W)).:
- -
- -
HIGHEST_32_BITS(X) 32 X, SIN(j+1) ;
- -
- -
"1". "0", 512 448. , 64- , . 512 .
512- , 16 32- X[0]...X[15], , (H[0],H[1],H[2],H[3]):
(A,B,C,D) = (H[0],H[1],H[2],H[3]) j 0 15 T = (A + f(B,C,D) + x[z[j]] + y[j]) ROL s[j] (A,B,C,D) = (D,B+T,B,C)_ j 16 31 T = (A + g(B,C,D) + x[z[j]] + y[j]) ROL s[j] (A,B,C,D) = (D,B+T,B,C)_ j 32 47 T = (A + h(B,C,D) + x[z[j]] + y[j]) ROL s[j] (A,B,C,D) = (D,B+T,B,C)_ j 48 63 T = (A + k(B,C,D) + x[z[j]] + y[j]) ROL s[j] (A,B,C,D) = (D,B+T,B,C)_(H[0],H[1],H[2],H[3]) = (H[0]+A,H[1]+B,H[2]+C,H[3]+D), 512- , H[0],H[1],H[2],H[3], 128- -.
MD5, MD4, . MD5 MD4. , MD4 48 , MD5 - 64. , MD4 ", " . . MD4, . , 1995 , , .. "-" , , "" (.. ASCII- "" ) - .
|
|