The rules for auras are actually a little complicated, see the whole 303.4 rule for more. what you're asking for is:

303.4a An Aura spell requires a target, which is restricted by its enchant ability.

702.5a Enchant is a static ability, written "Enchant [object or player]." The enchant ability restricts what an Aura spell can target and what an Aura can enchant.

For equipments, there is the rule for equip:

702.6a Equip is an activated ability of Equipment cards. "Equip [cost]" means "[Cost]: Attach this Equipment to target creature you control. Activate this ability only any time you could cast a sorcery."

The next thing is that only spells and abilities can have targets. I didn't find that explicitly, but this is also good:

113.9a Just because an object or player is being affected by a spell or ability doesn't make that object or player a target of that spell or ability. Unless that object or player is identified by the word "target" in the text of that spell or ability, or the rule for that keyword ability, it is not a target.

To sum everything up, it's like that: Only spells and abilities have targets, permanents don't. However, the enchant keyword lays restrictions on the enchanted object much like with targeting. that's why no white aura grants protection from white. Shroud only disallows targeting and does therefore not influence the pacifism.