This is not impossible. 2^600 is approximately 1e19. Considering there are 92 strands of DNA in a single cell, and around 37 trillion cells in a human body, a quick calculation means you need to dig up around 3000 bodies. Of course, this isn't exact (I haven't taken soft tissue decay into account, for instance), but the job is made somewhat easier by being able to piece together broken strands of DNA