Laser line and the marker at k·G: what the forge is doing nowThe potato: its scanned width sets a, its height sets bA potato turns on a turntable under a laser line scanner. The cut it makes sets the curve y² = x³ + ax + b on the display, with a from the scanned width and b from the height. Each crank turn adds the generator G once more, so the marker walks to k·G by chord and reflection. The printer takes the same a and b over the prime 2⁶¹ − 1 and prints the x coordinate of k·G as a 16-digit hex key; k, the crank count, is the secret.