Appearing in the seminal paper by Diffie and Hellman, the first published public

Question

Appearing in the seminal paper by Diffie and Hellman, the first published public-key algorithm that defined public-key cryptography [DIFF76] is referred to as the Diffie-Hellman key exchange (Stallings & Brown, 2008, p. 641). Define the Diffie-Hellman key exchange? How is this information relevant to you? What is the purpose of the algorithm? Be specific. How does it work? Give an example from personal experience or one that you have read about. What would be an appropriate implementation in an organization for the algorithm? In what types of organizations would this be appropriate?

Explanation / Answer

Purpose: Diffie Hellman algorithm is meant for secure key exchange between two parties.

After exchanging secure key ,then any public key algorithm can be used to encrypt and decrypt based on keys; this is only key exchange algorithm.

The exchange depends on discrete logarithm computation.

Diffie Hellman working process:

Intially both parties agree on prime number P and generator g ,forms a public key

user Alice : chooses private key x; computes : A=gx mod P , sends A to user B (BOB)

user BOB:choose private key y ; computes B=gymod P and sends B to user A(Alice)

now Alice computes K=gxB mod P

Bob computes Kl=gyAmod P;  

Now the computed values of both parties K=Kl are equal.

Thus keys are securely exchanged.

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key exchange can be done in many ways, sending encrypted key on previous key agreement.

By exchanging key via trusted third party . but diffie hellman is secure as it is difficult to find x value in y=gx mod P. even if the values of g,P, Y are public values.

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key exchange algorithms are needed to carry out secure communication; which needs to exchange keys so that both sender and receiver can agree on public key algorithms.

organizations which implement secure session establishment needs this algorithm.To establish secure session between client and server this key exchange is useful.

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