SCB: Flexible and Efficient Asymmetric Computations Utilizing Symmetric Cryptosystems Implemented with Intel SGX

The wide spread of cloud computing and the rapid growth of online activities raise the demand for privacy enhancing cryptography, such as identity-based encryption (IBE), attribute-based encryption (ABE), and group/ring signature, which are mostly asymmetric. However, implementing a practical asymmetric cryptosystem with privacy enhancing functionalities faces the big challenge of large computing overhead that stems from the hard mathematical problems they are based on, which in reality hinders the further deployment of such cryptosystems.In this paper, we propose "SGX Cipher Box" (SCB), a method of constructing flexible and efficient asymmetric computations by encapsulating symmetric algorithms into Intel SGX enclaves. Two types of enclaves are designed for serving computations with the public key and the private key, respectively. The security assumptions of asymmetric algorithms can be achieved in SCB based on guarantees offered by SGX. SCB is of great flexibility that it facilitates implementing various asymmetric computations with limited enclaves. We present four SCB-based cryptosystems, provisioning asymmetric primitives, IBE, ABE, and ring signature, respectively. The four prototype cryptosystems are implemented and benchmarked in terms of computing efficiency. Experimental results show that SCB surpasses conventional asymmetric cryptosystem implementations in performance.