ex.-no-2-c-implementation-of-diffie-hellman-key-exchange-algorithm's Introduction

EX.-NO-2-C-IMPLEMENTATION-OF-DIFFIE-HELLMAN-KEY-EXCHANGE-ALGORITHM

AIM:

To implement the Diffie-Hellman Key Exchange algorithm using C language.

ALGORITHM:

STEP-1: Both Alice and Bob shares the same public keys g and p.

STEP-2: Alice selects a random public key a.

STEP-3: Alice computes his secret key A as g a mod p.

STEP-4: Then Alice sends A to Bob.

STEP-5: Similarly Bob also selects a public key b and computes his secret key as B and sends the same back to Alice.

STEP-6: Now both of them compute their common secret key as the other one’s secret key power of a mod p.

PROGRAM:

# Diffie-Hellman Code

def prime_checker(p):
	if p < 1:
		return -1
	elif p > 1:
		if p == 2:
			return 1
		for i in range(2, p):
			if p % i == 0:
				return -1
			return 1


def primitive_check(g, p, L):
	for i in range(1, p):
		L.append(pow(g, i) % p)
	for i in range(1, p):
		if L.count(i) > 1:
			L.clear()
			return -1
		return 1
l = []
while 1:
	P = int(input("Enter P : "))
	if prime_checker(P) == -1:
		print("Number Is Not Prime, Please Enter Again!")
		continue
	break

while 1:
	G = int(input(f"Enter The Primitive Root Of {P} : "))
	if primitive_check(G, P, l) == -1:
		print(f"Number Is Not A Primitive Root Of {P}, Please Try Again!")
		continue
	break

# Private Keys
x1, x2 = int(input("Enter The Private Key Of User 1 : ")), int(
	input("Enter The Private Key Of User 2 : "))
while 1:
	if x1 >= P or x2 >= P:
		print(f"Private Key Of Both The Users Should Be Less Than {P}!")
		continue
	break

# Calculate Public Keys
y1, y2 = pow(G, x1) % P, pow(G, x2) % P

# Generate Secret Keys
k1, k2 = pow(y2, x1) % P, pow(y1, x2) % P

print(f"\nSecret Key For User 1 Is {k1}\nSecret Key For User 2 Is {k2}\n")

if k1 == k2:
	print("Keys Have Been Exchanged Successfully")
else:
	print("Keys Have Not Been Exchanged Successfully")