The Rings of Power
Obi-Gandalf Olorin

At the time of the forging of the Rings of Power, Sauron cast a fair image of himself to allow him to get in close and learn the Elvish secrets, but also he gave gifts of knowledge which helped Celebrimbor to creat the rings. Noone knew of his true nature until he placed the One upon his finger. If Celebrimbor had been aware that he was dealing with the same Maia who had been Morgoth's chief lieutenant, he quite possibly would never have created the Rings for his people or others. The Nine and Seven Sauron tainted with his power so that they would fall easily under his dominion, once agian presenting them as gifts (to the dwarves, the promise of wealth, to Men great power of command and sourcery), and only the Nine actually came under his control, as of the Seven, they were either consumed or gathered to him. the dwarves were too resilient to bend to his will, or why else would he have seized the dwarven Ring that Thorin's grandfather possessed when he was a prisoner in Dol Guldur? Only the Three were untouched by Sauron, purely because Celebrimbor wished to create them by himself and he did doubt Sauron. Obviously, he realised Sauron's treachery early enough to hide the Three, but he was not able to escape when Sauron appeared at Eregion with an army.