The quest Unfathomable Depths , given by the Argonian From-Deepest-Fathoms in Riften, gives you a perk named Ancient Knowledge. It gives you a permanent 25% bonus to armor when wearing a full set of Dwarven armor, the perk also allows blacksmithing to increase at a 15% faster rate. At legendary quality a full set of Dwarven armor with the perk is equal to, if not slightly above maxed Daedric, seeing as how it has no armor bonuses compared to Dwarven.
Source:- http://elderscrolls.wikia.com/wiki/Dwarven_Armor_%28Skyrim%29
BUT
The Ancient Knowledge perk is currently bugged; The bonus to Dwarven Armor does not work as listed, instead seeming to enhance armor rating from ALL heavy AND light armor, rather than only dwarven; This commonly leads to the assumption that the effect doesn't work at all, since the way one would expect to see it change is by comparing armor rating before and after equipping. Also, instead of making the Blacksmithing skill increase 15% faster, it actually fortifies Blacksmithing.
Source:- http://elderscrolls.wikia.com/wiki/Unfathomable_Depths