ASP.NET 2.0 Diffie-Hellman Example

Diffie-Hellman is a standard method of Alice and Bob being able to communicate, and end up with the same secret encryption key. Initially the values of G and N are defined:

Click here first ....

Next Bob and Allice will calculate an X value and a Y value, respectively:

Bob X Value		Alice's Y value
	Next ...
Bob's A value		Alice's B value
	A=G^x mod N		B=G^y mod N

and Bob will send his A value to Alice, and Alice will send her B value to Bob, and they now re-calculate the values to generate the same shared key:


	Finally ...
Bob's Key		Alice's Key
	Key=B^x mod N		Key=A^y mod N

Then, as if by magic Bob and Alice have the same secret key. Obviously this example uses small 64-bit integers, but it shows the principle.

protected void Button3_Click(object sender, EventArgs e)
{
Random val = new Random();

X.Text = Convert.ToString(val.Next(10));
Y.Text = Convert.ToString(val.Next(10));
G.Text=Convert.ToString(val.Next(50));
N.Text=Convert.ToString(val.Next(200)+10);
}

protected void Button1_Click(object sender, EventArgs e)
{
double g, n, x, y;
long a, b;

g = Convert.ToDouble(G.Text);
n = Convert.ToDouble(N.Text);
x = Convert.ToDouble(X.Text);
y = Convert.ToDouble(Y.Text);

a = Convert.ToInt64(Math.Pow(g, x)) % Convert.ToInt64(n);
b = Convert.ToInt64(Math.Pow(g, y)) % Convert.ToInt64(n);

A.Text = Convert.ToString(a);
B.Text = Convert.ToString(b);
}

protected void Button2_Click(object sender, EventArgs e)
{

double g, n, x, y;
long a, b;

g = Convert.ToDouble(G.Text);
n = Convert.ToDouble(N.Text);
x = Convert.ToDouble(X.Text);
y = Convert.ToDouble(Y.Text);
a = Convert.ToInt64(A.Text);
b = Convert.ToInt64(B.Text);

this.BobKey.Text = Convert.ToString(Convert.ToInt64(Math.Pow(b, x)) % Convert.ToInt64(n));
this.AliceKey.Text = Convert.ToString(Convert.ToInt64(Math.Pow(a, y)) % Convert.ToInt64(n));

}

and an example: