Modern embedded systems manage sensitive data increasingly often through cryptographic primitives. In this context, side-channel attacks, such as power analysis, represent a concrete threat, regardless of the mathematical strength of a cipher. Evaluating the resistance against power analysis of cryptographic implementations and preventing it, are tasks usually ascribed to the expertise of the system designer. This paper introduces a new security-oriented data-flow analysis assessing the vulnerability level of a cipher with bit-level accuracy. A general and extensible compiler-based tool was implemented to assess the instruction resistance against power-based side-channels. The tool automatically instantiates the essential masking countermeasures, yielding a ×2.5 performance speedup w.r.t. protecting the entire code.

Security has been identified as a critical dimension in the design of embedded systems for almost a decade. A wellrecognised critical threat against the security of embedded systems is represented by 'side-channel attacks (SCAs)', which mandate the application of specially tailored countermeasures. These countermeasures are significantly demanding in terms of computation effort, and have traditionally been applied by hand. The recent introduction of a methodology to gauge the security margins provided by software cipher implementations, allows the integration of the automated application of countermeasures into platform-based system-level design methodologies. The authors introduce in the design space of block cipher implementations a new metric concerning the resistance against SCAs, provide a systematic method for the selection of the most appropriate cipher given the security and performance trade-offs, and point out the performance requirements for the random number generator. Moreover, they discuss the implications of the design space extension on system runtime adaptivity. The experimental evaluation demonstrates that a single cipher does not cover optimally a range of convenient operating points and that ciphers like a Serpent, which are considered slow in non-protected implementations, can outperform primitives like the Advanced Encryption Standard when implementations with equal security guarantees against SCAs are considered.