overengineered? you do realise that fixed point integer math done with CPUs is how all games did shit before GPUs, before FPUs how would you distribute a file. let me see. oh yes! HTTP!

seriously though. did i say anything about the network protocol part of this? nope. i was just saying, you can make a scale operation, that can be repeated by any other holder of the original, attested, and the small version distributed, with relay hints (blossom hints?) to where you can get the original... IF YOU MUST. the only "complicated" part is the algorithm should be deterministic so that anyone with the original, can create the same scaled down version, and so that anyone who knows the origin of the original (eg, the artist/photographer) can see that bob, charlie and dave all saw this same image with this same hash and that they also performed this cheap scaling operation one time and then signed on a document saying so. doesn't take that many of these to be strongly confirmed. i'm not sure what you were expecting, that's really simple, and only marginally difficult to do right now if you just use a few image libraries.