ExpSOS: Secure and Verifiable Outsourcing of Exponentiation Operations for Mobile Cloud Computing
This addresses the challenge of resource limitations in mobile cloud computing by enabling efficient and verifiable cryptographic computations, though it appears incremental as it builds on existing outsourcing schemes.
The paper tackles the problem of securely outsourcing expensive exponentiation operations to an untrusted server for mobile devices, achieving significant computational gains with a verification scheme that ensures valid results with probability approximately 1.
Discrete exponential operation, such as modular exponentiation and scalar multiplication on elliptic curves, is a basic operation of many public-key cryptosystems. However, the exponential operations are considered prohibitively expensive for resource-constrained mobile devices. In this paper, we address the problem of secure outsourcing of exponentiation operations to one single untrusted server. Our proposed scheme (ExpSOS) only requires very limited number of modular multiplications at local mobile environment thus it can achieve impressive computational gain. ExpSOS also provides a secure verification scheme with probability approximately 1 to ensure that the mobile end-users can always receive valid results. The comprehensive analysis as well as the simulation results in real mobile device demonstrates that our proposed ExpSOS can significantly improve the existing schemes in efficiency, security and result verifiability. We apply ExpSOS to securely outsource several cryptographic protocols to show that ExpSOS is widely applicable to many cryptographic computations.