Secure Outsourcing of Boneh-Franklin Identity-Based Encryption Scheme

In recent years pairing-based cryptographic protocols have attracted so much attention. Meanwhile identity-based cryptography based on bilinear pairings has received particular attention. The IEEE, IETF, and ISO organizations have been working on standardization of pairing-based cryptographic schemes. The Boneh-Franklin identity-based encryption is the most well-known identity-based scheme that has been standardized. So far, various schemes have been proposed to reduce the computational cost of pairing operations. All these schemes are trying to outsource pairing operations in a secure manner. But in addition to pairing operations, there are other basic and costly operations in pairing-based cryptography and identity-based schemes, including scalar multiplication on elliptic curves. In this research, we outsource the Boneh-Franklin encryption in a more secure and efficient (in terms of computational and communication complexity) way than existing schemes. The proposed scheme is secure in the OMTUP model. Also, unlike previous schemes, we considered communication channels insecure. Moreover, compared with the trivial solution which outsources every single operation (such as pairing, scalar multiplication and modular exponentiation) as a separate subroutine, our scheme offers less complexity by seamlessly outsourcing the whole encryption scheme for the first time.