Verifiable Side-Channel Security of Cryptographic Implementations: Constant-Time MEE-CBC
Autor: | José B. Almeida, François Dupressoir, Manuel Barbosa, Gilles Barthe |
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Rok vydání: | 2016 |
Předmět: |
0301 basic medicine
Provable security Correctness Computer science business.industry Distributed computing Cryptography 0102 computer and information sciences Adversary Computer security computer.software_genre 01 natural sciences Software development process 03 medical and health sciences Timing attack 030104 developmental biology Countermeasure 010201 computation theory & mathematics Side channel attack Software verification and validation business computer Formal verification Implementation Block cipher |
Zdroj: | Fast Software Encryption ISBN: 9783662529928 FSE |
Popis: | We provide further evidence that implementing software countermeasures against timing attacks is a non-trivial task and requires domain-specific software development processes: we report an implementation bug in the s2n library, recently released by AWS Labs. This bug now fixed allowed bypassing the balancing countermeasures against timing attacks deployed in the implementation of the MAC-then-Encode-then-CBC-Encrypt MEE-CBC component, creating a timing side-channel similar to that exploited by Lucky 13. Although such an attack could only be launched when the MEE-CBC component is used in isolation --- Albrecht and Paterson recently confirmed in independent work that s2n's second line of defence, once reinforced, provides adequate mitigation against current adversary capabilities --- its existence serves as further evidence to the fact that conventional software validation processes are not effective in the study and validation of security properties. To solve this problem, we define a methodology for proving security of implementations in the presence of timing attackers: first, prove black-box security of an algorithmic description of a cryptographic construction; then, establish functional correctness of an implementation with respect to the algorithmic description; and finally, prove that the implementation is leakage secure. We present a proof-of-concept application of our methodology to MEE-CBC, bringing together three different formal verification tools to produce an assembly implementation of this construction that is verifiably secure against adversaries with access to some timing leakage. Our methodology subsumes previous work connecting provable security and side-channel analysis at the implementation level, and supports the verification of a much larger case study. Our case study itself provides the first provable security validation of complex timing countermeasures deployed, for example, in OpenSSL. |
Databáze: | OpenAIRE |
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