Go to Venus. Wait for the pack of wolves at ember caves. Hit them fast and hard(Use the scorch cannon from the first wave. Shoot at the floor below incoming ships, let it charge and release when the enemies drop.). Kill all the wolves. There are 4 chest locations. Learn them. Loot your chest as many times as possible(can be done 2-4 times, depends on chest location and how fast you found it). Rush over to the citadel(right next to the ember Caves). Most times the Pack of wolves arrives just as you do, if you were quick enough to dispatch the ones at ember caves. Dispatch of the pack of wolves. There are four chest locations. Learn them. As soon as you kill the last wolf, stay on high ground and look at the chest locations from there. Loot 2-4 times depending on location and how fast you found it. Go back to Ember Caves. Repeat. Note: To loot more than once. Get on your sparrow and head to adjacent areas(Vault of glass Area, or ember caves, depending on where your chest spawned). As soon as the name of the area pops up on your screen, turn around and go back to the chest. Repeat until your ether key runs out. Also, there are times that the Citadel Pack won't spawn, so if 2 minutes go by at citadel and they don't arrive, go back to Ember Caves. Have your inventory full, when you farm you'll get tons of Special Ammo Synthesis you can't delete. Have a slot with heavy ammo Synth that's not full(Less than 20 at all times). You'll want to keep the heavy Synthesis you get. If you get legendary engrams or keys, and you're full, they are sent to the postmaster. Go get them ASAP. If you keep farming, the goodies will be replaced by blue crap at the postmaster.

Hate to say this but it's just RNG - I've spent 6 hours MAX farming for keys and only got my first at the 5 hour mark - I went and cashed it in right away, naturally. Stopped playing that night. Came on this morning and got a Treasure Key in my first chest opened. That said I do think they could do something like have one awarded with the Nightfall every week, atleast 1 chance to open the Treasure Chest a week.

I would love a new easier way to get treasure keys. I hate this key farming. Hopefully those bounties or a side chest will give me one this week.

I've seen people get keys from the chest that open up when you complete a HoW bounty

I've seen people get keys from the chest that open up when you complete a HoW bounty