Madara can achieve the rinnegan through the sharingan alone.. Just cause he is the shit & mastered the true power of sharingan..But if Tobi was Madara, then why did he need to implant Nagato's rinnegan instead of just transforming his sharingan. If he was Madara, then he should be able to do it too..Only makes sense..& Obito cant be Tobi because of two things.(1)Obito's whole right side was crushed by massive boulders, so his whole right side of his body/face had to be f#@$ up. But when you look at Konan & Tobi's fight, Tobi's mask crumbles & reveals a chunk of his right face. which didnt look like a boulder crushed it.(2) When Minato fought the masked man, they were the same age. While deceased tobi had to at least be 13.. I just wanted to punch a slight whole through the Madara & Obito theories because I just read blogs on it.