The title looks strange but it is to deal with this situation.
The data we have should only be accessible by our end user and data administrators, not anyone else. Ideally, each user should have different encryption key.
Even with administrators, I wish only when two of them agrees, then they could access the data by join two pieces of the key. I could think of doing this by breaking up the key into two half, and each one of them holds half the key.
Is there such a cryptography can achieve this? So the file could be decrypted by more than one key. Or any other recommendations?