Subject: Mobile Computing

Difficulty: Medium

Marks: 4 Marks

Deffie Hellman Algorithm:

Consider Alice and Bob want to exchange the key

1. Firstly, Alice and Bob agree on two large prime numbers, n and g. These two integers need not be kept secret. Alice and Bob can use an insecure channel to agree to them
2. Alice chooses another large random number x, and calculates A such that : A =$g^{x}$ mod n
3. Alice sends the number A to Bob.
4. Bob independently chooses another large random integer y and calculates B such that: B =$g^{y}$ mod n
5. Bob sends the number B to Alice.
6. A now computers the secret key K1 as follows: K1= $B^{x}$ mod n
7. B now computers the secret key K2 as follows: K2= $A^{y}$ mod n