Kiber-huquq va kiber-etika


Asosiy qism. Simmetrik shifrlash usullarini axborotni himoyalashda ishlatish


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Kiber-huquq va kiber-etika Saidxonov

2. Asosiy qism. Simmetrik shifrlash usullarini axborotni himoyalashda ishlatish.
2.1. A5/1 shifrlash algoritmi haqida (oqimli)
GSM tarmog‘ida ovozli so‘zlashuvlarni shifrlash uchun foydalaniladi.
A5/1 oqimli shifrlash algoritmida 64 bitli 𝐾 kalitdan foydalaniladi.
A5/1 shifrlash algoritmi uchta chiziqli siljitish registorlaridan iborat bo‘lib, kiritilgan kalit 𝐾 ularga bo‘lib yoziladi:
𝑋 registor o‘zida 19 bit (𝑥0,𝑥1,…,𝑥18)
𝑌 registor esa 22 bit (𝑦0,𝑦1,…,𝑦21)
𝑍 registor esa 23 bit (𝑧0,𝑧1,…,𝑧22)
Tasodifiy ketma-ketliklarni generatsiyalash
Berilgan uchta bit 𝑥8,10,𝑧10 asosida 𝑚=𝑚𝑎𝑗(𝑥8,𝑦10,𝑧10 ) funksiya qiymati hisoblanadi.
Masalan, (1,0,0)=0,𝑚𝑎𝑗(1,1,0)=1
Agar 𝑥8=𝑚 ga teng bo‘lsa, 𝑋 siljitiladi:
𝑡=𝑥13⨁𝑥16⨁𝑥17⨁𝑥18
𝑖=18,17,16,…,1 uchun 𝑥i=𝑥(i-1)
𝑥0=𝑡
Agar 𝑦10=𝑚 ga teng bo‘lsa, 𝑌 siljitiladi:
𝑡=𝑦20⨁𝑦21
𝑖=21,20,19,…,1 uchun 𝑦i=𝑦(i-1)
𝑦0=𝑡
Tasodifiy ketma-ketliklarni generatsiyalash
Agar 𝑧10=𝑚 ga teng bo‘lsa, 𝑍 siljitiladi:
𝑡=𝑧7⨁𝑧20⨁𝑧21⨁𝑧22
𝑖=22,21,20,…,1 uchun 𝑧i=𝑧(i-1)
𝑧0=𝑡
Shundan so‘ng tasodifiy ketma-ketlikning bir biti quyidagicha hisoblanadi:
𝑠=𝑥18⨁𝑦21⨁𝑧22
Yuqoridagi ketma-ketlik ochiq matnni uzunligiga teng bitlarni generatsiya qilguncha takrorlanadi.

Bunga misol tariqasida Ismimning bosh harfini shifrlaydigan bo’lsam:
T = E
K = XORAZMIY
T = 0100
K = 0101100001001111010100100100000101011010010011010100100101011001
X: 0101100001001111010
Y: 1001001000001010110100
Z: 10011010100100101011001
1:
maj(0,0,0) = 0
X, Y va Z registorlar suriladi
t = = 1 0 1 0 = 0
t = = 0 0 = 0
t = = 0 0 0 1 = 1
X: 0010110000100111101
Y: 0100100100000101011010
Z: 11001101010010010101100
C = 1 0 0 0 = 1
2:
maj(0,0,0) = 0
X, Y va Z registorlar suriladi
t = = 1 1 0 1 = 1
t = = 1 0 = 1
t = = 1 1 0 0 = 0

X: 1001011000010011110
Y: 1010010010000010101101
Z: 01100110101001001010110
C = 0 1 0 1 = 0
3:
maj(0,0,1) = 0
X, Y registorlar suriladi
t = = 0 1 1 0 = 0
t = = 0 1 = 1
X: 0001011000010011110
Y: 1010010010000010101101
Z: 11001101010010010101100
C = 0 1 0 0 = 1
4:
maj(0,0,0) = 0
X, Y va Z registorlar suriladi
t = = 0 1 1 0 = 0
t = = 0 1 = 1
t = = 1 1 0 0 = 0

X: 0001011000010011110
Y: 1010010010000010101101
Z: 01100110101001001010110
C = 0 1 0 0 = 1
C = 1011

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