SciDB's security


Hello all!
How the security is realized in SciDB? I want to make some algorithm, in which each SciDB user have some level of security. And I want, that this user can read and write data accordingly his security level. I think, that all array or it’s part has security level.
So, 1 - top secret, 2 - secret, 3 - not secret.
So, if user user1 has security level 2 (secret), he can read and write arrays of data with security level 2 and 3.

And one more question: can we make some authorization system like in PostgreSQL on pg_hba?

Thank you for answers.