Diffie-Hillman Key Exchange

1. Alice and Bob agree on two numbers y and p with 0 < y < p. These numbers are not private and can be known by anyone.

2. Alice picks a private number 0 < a and computes α = y^a mod p. Alice sends α to Bob.

3. Meanwhile, Bob picks a private number 0 < b and computes β = y^b mod p. He then sends β to Alice.

4. Alice computes k = β^a mod p and Bob computes k = α^b mod p. Both of them obtain the same number k which can then be used as the private key.