The EVVA 3KS (3 Kurven System in German, 3 Curve System in English) was developed in 1993, and still is considered one of the highest-security locks on the market today. There are 3 curves on each side of the key, which control 12 sliders in the lock. The key is reversible.  The curves are cut at 2 different depths. The curve that starts in the middle of the key is deeper than the two that start near the edges. Below is a picture of a 3KS key. The deepest curve is highlighted in green, and the two shallow curves are highlighted in blue. The control dimple is highlighted in red. 

There are also two slider variations; one has two pins and follows the outside waves, and the other has one pin and follows the middle wave. The two pin sliders have 7 variations, and the one pin slider has 9 variations. These springless sliders, once correctly positioned, allow 2 sidebars to drop into a notch on each slider, which allows the plug to rotate. There is one sidebar on each side of the lock. Once the key is turned, a roller drops into the control dimple near the bow of the key, which makes sure the key is kept into the lock until the cylinder is rotated back to it's locked position. Another security feature of the 3KS is the top profile bar. This bar checks the profile that is on the top and bottom (since the key is reversible) of the key. If the profile is not correct, the profile bar will not fall into the notches on the key, and this will block rotation of the plug. Below is a photo of the top profile. 

The 3KS is protected against picking, drilling, plug pulling, pulling off the cylinder, and breaking off the cylinder.