Creating key pairs for the Diffie-Hellman algorithm

- I'm here in the exercise files, 03_03_DiffieHellman. I've opened it in Excel, and I'm just gonna show you the exact same example that we just walked through. If we look here, on the left hand side, you see the Non-Secret Values. P is a Prime Number. And as you can see, we've selected 17. g, this is the Base. It's a Prime Number, but it is Smaller than P.

Here we've selected 5. On the right we see Secret Values. Alice's random secret integer, which Must be smaller than P. Alice selected 5. Then we see Bob's random secret integer. Must be smaller than P, and he selected 4. You see the calculations that take place, which is first, down again, over on the right hand side. g to the a power is gonna be your Av.

Then on the right hand side, we see the calculations that has taken place. MOD(AV,P) which is achieved by dividing Av by P and keeping the remainder, which gives us our A value. The same thing happens with Bob. He calculates Bv by using g to the b power. That is then incorporated to be MOD(Bv,P).

That value is 13, which is then sent to Alice. Alice then computes the Shared secret part a, by doing B to the a. And then the Shared secret part b, which is achieved by A to the b power. They both come up with the same conclusion. The Shared secret is 13. I hope seeing Diffie Hellman in action was helpful. Now I'd like you to try it. Go to the bottom and select To Try. Now, as you can see here, there's a place where you can put your Secret Values and a friend's Secret Value.

Now keep in mind, the Non-Secret Values over on the left hand side, you'll select two numbers, a Prime Number, and a Base. The Base must be a Prime Number, Smaller than P. Over on the right hand side, you're going to select a random secret integer that is smaller than P. Then your friend will select a secret integer, again smaller than P. It will then calculate the Shared secret, which will be the same.