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Smart cards are vulnerable to both invasive and non-invasive attacks. Specifically, non-invasive attacks using power and timing measurements to extract the cryptographic key has drawn a lot of negative publicity for smart card usage. The power measurement techniques rely on the data-dependent energy behavior of the underlying system. Further, power analysis can be used to identify the specific portions of the program being executed to induce timing glitches that may in turn help to bypass key checking. Thus, it is important to mask the energy consumption when executing the encryption algorithms.In this work, we augment the instruction set architecture of a simple five-stage pipelined smart card processor with secure instructions to mask the energy differences due to key-related datadependent computations in DES encryption. The secure versions operate on the normal and complementary versions of the operands simultaneously to mask the energy variations due to value dependent operations. However, this incurs the penalty of increased overall energy consumption in the data-path components. Consequently, we employ secure versions of instructions only for critical operations; that is we use secure instructions selectively, as directed by an optimizing compiler. Using a cycle-accurate energy simulator, we demonstrate the effectiveness of this enhancement. Our approach achieves the energy masking of critical operations consuming 83% less energy as compared to existing approaches employing dual rail circuits.

Silicon technology advances have made it possible to pack millions of transistors -switching at high clock speeds -on a single chip. While these advances bring unprecedented performance to electronic products, they pose difficult power/energy consumption problems. For example, large number of transistors in dense onchip cache memories consume significant static (leakage) power even if the cache is not used by the current computation. While previous compiler research studied code and data restructuring for improving data cache performance, to our knowledge, there is no compiler-based study that targets data cache leakage power consumption. In this paper, we present code restructuring techniques for array-based and pointer-intensive applications for reducing data cache energy consumption. The idea is to let the compiler to analyze the code and insert instructions that turn off cache lines that keep variables not used by the current computation. This turning off does not destroy contents of a cache line, and waking up the cache line incurs very little overhead. Due to data locality, we find that at a given time only a small portion of the data cache needs to be active; the remaining part can be placed into a leakage-saving mode (state); i.e., they can be turned off. Our preliminary results indicate that the proposed strategy reduces the cache energy consumption significantly. We also show that several compiler optimizations increase the effectiveness of our strategy.

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