Diffie-Hellman is cryptography protocol, which allows two users to exchange the key over the public cloud. Mainly VPN uses Diffie-Hellman algorithms to provide reliable and trusted method of key exchanges. The algorithm was being invented by Whitefiled Diffie and Martin Hellman in 1976. During DH exchange both users must agree on two non secret numbers which could be available publically or in the form of any certificate. After this agreement, users exchange their keys and come to know that their and remote user keys are same. After bona fied to each other, they start exchange their data.
In this post, I will explain how the keys values are calculated. First we need to define two public keys which are available through any certificate or via any other method to both users. Let’s assume n and g are public keys for user1 and user2. Value of g should be small and n(take big values) should be prime number.
Both users are having same keys initially.
n=997
g=2
Next step is to use the private keys and compute the value which should be given to remote user.
Private key for user1 is 3 and for user2 is 5.