You got it. Lasers are cheap... electronics are cheap... batteries are cheap... spoofing is cheap.
Really, as an engineer, I can imagine two ways for this thing to work, and it depends on if the projectile spins. Typically, bullets spin so that they act as gyroscopes -- always pointing the same direction (YouTube has videos of guys firing pistols into ice -- ice stops bullet which just sits there and spins like a top).
If the projectile spins, you can, in theory, guide it with a single fin that can extend or retract. You could not use a standard camera as such, because you are spinning wildly. Assume 2000 FPS bullets -- if you want to shoot a mile, you need at least this much. Also assume a 1-in-12 twist (real twists are in the range of 1-in-7 to 1-in-14, depending on shape and weights of bullet). That means that the bullet is spinning with a approximate rotation of 2 KHz. I doubt that you could have an effective regular camera spinning like that and still work. A better way would be to have a linear sensor (a line camera) that looks forward and to the side. This could operate. When you see a bright stop, see how far it is from the center. More off-center = kick your fin a bit more. This is simple and straightforward. However, since the bullet is spinning and you do not know when the camera will cross the laser, you probably need to keep the laser on full time. This is probably the easiest and cheapest way to accomplish this, but should be easily spoofed. You could maybe put a crypto on the laser signal by changing the intensity of the signal without turning it off, but it would have to be a much lower frequency than 2 KHz because that is your effective sample rate. If you assume 500 Hz signal (four-times oversampling), you would only get about 500 bits of data before you hit your target (assuming a target 2000 feet away). Is that enough to actually apply crypto? I am not sure...
On the other hand, if the bullet is NOT spinning, you can use a regular camera and regular fins to control it. In that case, it is entirely reasonable to embed some sort of cryptographic modulation on the signal. In any case, the existence of a 2-D sensor makes the bullet more expensive, and increases the amount of processing that needs to be done. It should, however, be more feasible to put crypto, but at greater cost.