Randomly generated 3D points on sphere surface

I am generating 3D points and process them 3D rotation:

var Points = [] ;
for (var i=0 ; i < 20 ; i++) {
    Points[i] = [
        Math.floor(Math.random()*256),
        Math.floor(Math.random()*256),
        Math.floor(Math.random()*256)
    ] ;
}
Process3DRotation() ;

But how to generate randomly 3D points on a hidden shpere like this: