June 16th, 2012, 10:05 AM
Join Date: Jun 2012
Time spent in forums: 22 m 20 sec
Reputation Power: 0
Crypto Algorithm Question - Why use prime and primitive root in Diffie-Hellman Algorithm
Hi guys, I just learned about this PKCS and I have 2 question to ask.....
p = prime number , q = primitive root of p
user A and B share : q and p
user A and B generate a secret key : i and j
user A and B use "q^i/j mod p" to generate exchange key : Xa and Xb
user A and B exchange key and generate session key.
1. Why use prime number and primitive root rather than 2 random number
2. Possible information get by hacker is q, p, Xa and Xb
hacker use brute force attack on Xa^n mod p , the hacker is trying to find out value i or j by keep try
for (n=1;;n+1), so the hacker will get the session key easily if the i and j value is low
SO, what is the minimum value for i and j