How to hide your valuables in Minecraft?

People are always stealing my diamonds and other hard-to-find items. How can I hide them well enough to be sure no-one would steal them while I'm exploring? I've seen some ideas but none of them seemed to work. Are there any traps or other stuff that might help?

Edit: It's a vanilla server without any OPs (except the admin of course).

Solution 1:

Place your valuables in an Ender Chest. Each player has their own Ender Chest space, so if someone would look in the Ender Chest you've put your diamonds in, they only see their own stuff they have put in an Ender Chest.

Solution 2:

Another suggestion is to have an underground base, and store your items in droppers. This makes it hard to find your base for people with hacks like X-ray and chestfinder, which lights up chests. A dropper is moderately efficient as it has 9 slots and can be crafted with seven cobblestone plus one redstone dust.