Timing side-channels are arguably one of the main sources of vulnerabilities in cryptographic implementations. One effective mitigation against timing side-channels is to write programs that do not perform secret-dependent branches and memory accesses. This mitigation, known as “cryptographic constant-time”, is adopted by several popular cryptographic libraries.
This paper focuses on compilation of cryptographic constant-time programs, and more specifically on the following question: is the code generated by a realistic compiler for a constant-time source program itself provably constant-time? Surprisingly, we answer the question positively for a mildly modified version of the CompCert compiler, a formally verified and moderately optimizing compiler for C. Concretely, we modify the CompCert compiler to eliminate sources of potential leakage. Then, we instrument the operational semantics of CompCert intermediate languages so as to be able to capture cryptographic constant-time. Finally, we prove that the modified CompCert compiler preserves constant-time. Our mechanization maximizes reuse of the CompCert correctness proof, through the use of new proof techniques for proving preservation of constant-time. These techniques achieve complementary trade-offs between generality and tractability of proof effort, and are of independent interest.
Fri 24 Jan
|15:35 - 15:56|
Gilles BartheMPI for Security and Privacy (MPI-SP) and IMDEA Software Institute, Sandrine BlazyUniv Rennes- IRISA, Benjamin GregoireINRIA, Rémi HutinIRISA / ENS Rennes, Vincent LaporteInria, David PichardieUniv Rennes, ENS Rennes, IRISA, Alix TrieuAarhus UniversityLink to publication DOI Media Attached File Attached
|15:56 - 16:18|
Youngju SongSeoul National University, Minki ChoSeoul National University, Dongjoo KimSeoul National University, Yonghyun KimSeoul National University, South Korea, Jeehoon KangKAIST, Chung-Kil HurSeoul National UniversityLink to publication DOI Media Attached File Attached
|16:18 - 16:40|
Timothy BourkeInria / École normale supérieure, Lélio BrunENS/Inria, Marc PouzetÉcole normale supérieureLink to publication DOI Media Attached File Attached