An In-Depth Evaluation of Externally Amplified Coupling (EAC) Attacks - A Concrete Threat for Masked Cryptographic Implementations

Ofek Gur, Tomer Gross, Davide Bellizia, Francois Xavier Standaert, Itamar Levi

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Masking is a systematic countermeasure to achieve side-channel security for cryptographic algorithms. However, its secure implementation relies on an independence assumption that can be violated by signal coupling. It has been established that coupling induced within a device can be detrimental. It was demonstrated on a 1st -order secure design (i.e., with two shares) that an adversary who can manipulate the design's power-measurement setup can externally induce significant coupling. It can thus concretely reduce the 'effective-security-order', i.e., make 1st -order leakages as significant as 2nd -order ones with fewer measurements. This paper explores the impact of such external amplification phenomena on fabricated hardware test cases for the first time. We designed a dedicated ASIC to extend the empirical results for demonstrating impact up to the 4th order. We have systematically evaluate d factors related to adversarial control, e.g., the external measurement resistance. We also investigate d their relative influence compared to intra-design ones, i.e., internal power-grid resistance and transistors' inherent resistance. Our study demonstrates that externally amplified coupling scale s up to concrete masked hardware designs with various amounts of shares and is not very sensitive to intra-design parameters. Therefore, providing experimental evidence that such coupling should be considered during masking validation.

Original languageEnglish
Pages (from-to)783-796
Number of pages14
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Issue number2
StatePublished - 1 Feb 2023

Bibliographical note

Publisher Copyright:
© 2004-2012 IEEE.


  • Coupling
  • EAC
  • effective security order
  • externally-amplified-coupling
  • masking
  • side-channel analysis


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