MEGA removes 3D gun design: ok but how?

The news:

http://www.pcworld.idg.com.au/article/461634/legal_fog_kim_dotcom_removes_3d_gun_design/

Rather than going into a discussion if this is right or wrong, I would like to understand how MEGA can remove some files when they claim that everything is encrypted (and therefore they should not be able to see what is stored in users' accounts).

any idea?

 

Every file is connected to a download link, so it seems to me if they know the link they can delete the file, even if they can't see what it is because it is encrypted, which they could in this case because the decryption key is public:

 

Ok but in this way I guess they can just detect the first step of sharing.
If, for example, I have that file and I share myself with my contacts (thus changing the decryption keys with my own ones) it's should not be possible to track it any longer.

 

I recall Steve Gibson from Security Now saying that there was pretty much no security on Mega. While they offer a massive amount of storage, I wouldn't trust it or use it.

 

Because MEGA isn't stupid enough to risk going through what they already have and have made damned sure they can CYA themselves. MEGA is not as secure as many believe, and it's also under the microscope of the U.S and everyone else interested in making sure Kim doesn't get out of hand again.

As to the design? Too late. It's on the internet, and it won't leave the internet. You cannot remove every instance of a file you don't like from every nook and cranny of the web. Anyone opposed to 3D printing of "bad things" knew good and well that this sort of thing would happen, so really there's not much room for complaining. It happens with every new advance in technology and you can't tell technology that it can only be used in such and such ways. Technology doesn't care what you think.