Kiberxavfsizlik asoslari

III. Эl-Gamal algoritmi. A tomon o‘zining maxfiy kaliti asosida ochiq kalit juftini hosil qiladi va uni B tomonda yuboradi. Olingan qiymatlar quyidagilar:
g=3; p=31; a=4; y=(g^a)modp=(3^4)mod31=19. Bu erda (p,g,y) – ochiq kalitlar jufti va a maxfiy kalit.
Shifrlash. Bu bosqich A tomonning ochiq kalitlariga эsa B tomondan amalga oshiriladi. Ochiq ma’lumot sifatida M=CDEF (2,3,4,5 –alfavitdani o‘rni) olinib, ЭKUB( , ) =1 shartni qanoatlantiruvchi k=7 tanlandi. Shundan so‘ng quyidagilar hisoblanadi:
r=(g^k)modp=(3^7)mod31=17;
C1=m*y^k=2*(19^7)mod31=14;
C2=m*y^k=3*(19^7)mod31=21;
C3=m*y^k=4*(19^7)mod31=28;
C4=m*y^k=5*(19^7)mod31=4;
Shundan so‘ng C1,C2,C3,C4 lardan iborat S va r A tomonga yuboriladi.
Deshifrlash. Bu jarayon maxfiy kalitga эga bo‘lgan A tomondan amalga oshiriladi va ochiq matn olinadi:
M1=C1*r^(p-1-a)modp=14*17^(31-1-4)mod31=2;
M2=C2*r^(p-1-a)modp=21*17^(31-1-4)mod31=3;
M3=C3*r^(p-1-a)modp=28*17^(31-1-4)mod31=4;
M4=C4*r^(p-1-a)modp=4*17^(31-1-4)mod31=5.

Nazorat savollari

1. 
   Klassik shifirlash algoritimllarini tushintiring?
   
2. 
   Ochiq va yopiq kalit nima?
   
3. 
   Birinchi shifirlash usullaridan biri qaysi hisoblanadi?
   
4. 
   Shifirlash va deshifirlashning farqi nima?
   
5. 
   Yana qanday shifirlash usullarini bilasiz?
   

Adabiyotlar ro‘yhati

1. 
   “Kiberxavfsizlik asoslari” S.K.Ganiyev, A.A.Ganiyev, Z.T.Xudoyqulov “Aloqachi” Toshkent 2020
   
2. 
   Cybersecurity Curricula 2017 – Curriculum Guidelines for Post-Secondary Degree Programs in Cybersecurity (ACM, IEEE-CS, AIS SIGSEC, IFIP WG 11.8) (Crosscutting concepts)
   
3. 
   ISO/IEC 27000 Information technology. Security techniques. Information security management systems. Overview and vocabulary.
   
4. 
   G’aniyev S. K., Karimov M. M., Tashev K. A. “Axborot xavfsizligi”, “Fan va texnologiyalar” nashriyoti, Toshkent 2016
   
5. 
   Mark Stamp. Information security. Principles and Practice. Second edition. A John Wiley& Sons, Inc., publication. Printed in the United States of America. 2011y. 584 p.
   
6. 
   Шангин В.Ф. «Информасионная безопасност компютерных систем и сетей», Учебное пособие. Издателский Дом "ФОРУМ" ИНФРА-М.: 2018 г.