Encrypt Amazon RDS

I want to create a RDS with MySQL on it, and I want it to be encrypted.

I am using the Ruby API, and I've looked into the RDS client API, and I saw that there are params that can be given:

tde_credential_arn
tde_credential_password

but both are related to oracle DB (Encrypting Amazon RDS Resources). I've also tried to use key storage_encryped and give it a true value, but the key wasn't a valid one (also I've seen it here: CreateDBInstance).

So, how can i do it with MySQL RDS ?