Point addition

Let's assume that P and Q are two points on the elliptic curve. P is not equal to Q; they are two distinct points on the curve. Point addition is explained geometrically as follows:

The following steps are performed on the elliptic curve as shown in Figure 2.7 to add two points.

1. Draw a straight line between points P (x1, y1) and Q (x2, y2)
2. The line will intersect the elliptic curve at point R1
3. A reflection of point R1 about the x axis gives point R (x3, y3), which is the result of the addition of P and Q