[Overtaxed]

It's in The Silmarillion chapter "Of the Rings of Power and the Third Age (I don't have ROTK with me at work today...it could be in the Appendices somewhere.) Sauron is in disguise as Annatar, Lord of Gifts:

In those days the smiths of Ost-in-Edhil surpassed all that they had contrived before; and they took thought, and they made Rings of Power. But Sauron guided their labours, and he was aware of all that they did; for his desire was to set a bond upon the Elves and to bring them under his vigilance.

Now the Elves made many rings; but secretly Sauron made One Ring to rule all the others, and their power was bound up with it, to be subject wholly to it and to last only so long as it too should last

[Penny1]

....ah-hah, it must have been the "Sauron guided their labors" that made me think that he helped them develop the "ring technology."

Thanks for looking that up, OT....