Diffie-Hellman Security relies on the difficulty of computing logarithms in these fields discrete logarithms takes O(e log n loglog n)operations The algorithm two people alice and Bob who wish to exchange some key over an insecure communications channel They select a large prime p( 200 digit), such as(p 1)/2 should also be prime They also select g, a primitive root mod p g is a primitive if for each n from 0 to p-1, there exists some a where ga=n mod p5 Diffie-Hellman • Security relies on the difficulty of computing logarithms in these fields – discrete logarithms takes O(e log n log log n) operations • The algorithm: – two people Alice and Bob who wish to exchange some key over an insecure communications channel. – They select a large prime p (~200 digit), such as (p- 1)/2 should also be prime – They also select g, a primitive root mod p • g is a primitive if for each n from 0 to p-1, there exists some a where ga = n mod p