This paper proposes a conceptually simple but practical management of outsourced data for provably secure duplicate elimination with efficient storage utilization. We focus on cutting off dependency of encryption key on underlying plain data, making data owners relieved from information leakage as long as their keys are kept secret. Rather than forcing data owners for the same content to share the same key, we restrict storage space in which duplicate identification and elimination occur in order to increase (de)duplication ratio. This allows data owners to choose their own keys with no restriction, and eventually the security of the proposed approach would not be affected by other data owners as well as inside and/or outside adversaries. Our approach can be adaptively applied to existing remote storage systems according to storage capacity and security requirements.