If trickery is the goal then you could for example hash a seed using a strong hash function. Output the hash bytes and feed the hash back in. You have random lo

If trickery is the goal then you could for example hash a seed using a strong hash function. Output the hash bytes and feed the hash back in. You have random looking data that should pass statistical tests (dieharder et al). This question arises with hardware RNGs - could some of them just output random looking data that the dark-powers know the seed of?