Telekommunikatsiya texnologiyalari fakultеti 931-19 guruhi talabasi Masharipov Saidabdullaning Kiberxavfsizlik asoslari

0	A	11	L	22
W
1	B	12	M	23	X
2	C	13	N	24	Y
3	D	14	O	25	Z
4	E	15	P	26	\
5	F	16	Q	27	/
6	G	17	R	28	{
7	H	18	S	29	}
8	I	19	T	30	[
9	J	20	U	31	$
10	K	21	V	32	#

Axborotni rasshifrovka qilishda quyidagi munosabatdan foydalaniladi:

X(i)=(Y(i))^d (modn).
Misol. so‘zini shifrlash va rasshifrovka qilish talab etilsin. Dastlabki so‘zni shifrlash uchun quyidagi qadamlarni bajarish lozim.
1-qadam. p=3 va q=11 tanlab olinadi.
2-qadam.n=3*11=33 hisoblanadi.
3-qadam. Eyler funksiyasi aniqlanadi.

4-qadam. O‘zaro tub son sifatida d=3 soni tanlab olinadi.
5-qadam. shartini qanoatlantiruvchi e soni tanlanadi. Aytaylik, e=7.
6-qadam. Dastlabki so‘zning alfavitdagi xarflar tartib raqami ketma-ketligiga mos son ekvivalenti aniqlanadi.
Blok uzunligi butun sonlar ichidan shartini qanoatlantiruvchi minimal son sifatida aniqlanadi. n= 33 bo‘lganligi sababli =6.
Demak, dastlabki Saidabdulla matni
X(i) ≤ < 18, 0, 8, 3, 0, 1, 3, 20, 11, 11, 0 >
ketma-ketlik ko‘rinishida ifodalanadi.
7-qadam. X(i) ketma-ketligi ochiq kalit {3,33} yordamida shifrlanadi:
T = SAIDABDULLA
Y(1)=(S) =18^3 (mod 33) = 24 = Y
Y(2)=(A) = 0^3 (mod 33) = 0 = A
Y(3)=(I) = 8^3 (mod 33) = 17 = R
Y(4)=(D) = 3^3 (mod 33) = 27 = /
Y(5)=(A) = 0^3 (mod 33) = 0 = A
Y(6)=(B) = 1^3 (mod 33) = 1 = B
Y(7)=(D) = 3^3 (mod 33) = 27 = /
Y(8)=(U) = 20^3 (mod 33) = 14 = O
Y(9)=(L) = 11^3 (mod 33) = 11 = L
Y(10)=(L) = 11^3 (mod 33) = 11 = L
Y(11)=(A) = 0^3 (mod 33) = 0 = A

T1 = YAR/AB/OLLA

Shifrlangan so‘z Y(i)=< 24, 0, 17, 27, 0, 1, 27, 14, 11, 11, 0>

Shifrlangan so‘zni rasshifrovka qilish maxfiy kalit {7,33} yordamida bajariladi.:
Y(1) = (24^7)(mod 33) = 18
Y(2) = (0^7)(mod 33) = 0
Y(3) = (17^7)(mod 33) = 8
Y(4) = (27^7)(mod 33) = 3
Y(5) = (0^7)(mod 33) = 0
Y(6) = (1^7)(mod 33) = 1
Y(7) = (27^7)(mod 33) = 3
Y(8) = (14^7)(mod 33) = 20
Y(9) = (11^7)(mod 33) = 11
Y(10) = (11^7)(mod 33) = 11
Y(11) = (0^7)(mod 33) = 0

Dastlabki son ketma-ketligi rasshifrovka qilingan

X(i) ≤ < 18, 0, 8, 3, 0, 1, 3, 20, 11, 11, 0 >

ko‘rinishida dastlabki matn <SAIDABDULLA> bilan almashtiriladi.