Cloud security is one of the most important issues in practice of cloud computing. In this paper, the authors proposed a crypto cloud infrastructure which is inherently constructed using asymmetric cryptography. Different to the prevalent Public Key Infrastructure (PKI) system, the crypto cloud is based on a self-authentication key system. Every component in the crypto-cloud has its own identity for data encryption and decryption. Such cipher functions can be provided to users as a service, or crypto as a service.