Optimizing public-key encryption for wireless clients

Providing acceptable levels of security imposes significant computational requirements on wireless clients, servers, and network elements. These requirements are often beyond the modest processing capabilities and energy (battery) resources available on wireless clients. The relatively small sizes of wireless data transactions imply that public-key encryption algorithms dominate the security processing requirements. In this work, we propose techniques to improve the computational efficiency of public-key encryption algorithms. We focus on modular exponentiation based encryption/decryption, which is employed in many popular public key algorithms (e.g., RSA, El Gamal, Diffie-Hellman etc.). We study an extensive suite of algorithmic optimizations to the basic modular exponentiation algorithm, including known optimizations such as Chinese Remainder Theorem, Montgomery Multiplication, etc., and new advanced techniques such as input block size selection, computation re-use through algorithm-level caching, etc. The proposed algorithmic optimizations lead to an “algorithm design space”, across which performance varies significantly (over an order-of-magnitude). We evaluated the proposed algorithmic optimization techniques by obtaining processing times for the SSL handshake protocol on a state-of-the-art embedded processor, when using the optimal algorithm configuration as well as a popular conventional algorithm configuration. The results demonstrate that the optimum algorithm configuration leads to a 5.7X improvement in SSL handshake protocol processing times. The proposed techniques are complementary to, and can be applied in conjunction with, improvements in security mechanisms and protocols, new hardware architectures, and improvements in silicon technologies.