In a development that addresses a long-standing theoretical tension in hardware security, researchers Francesco Berti of the Royal Military Academy and Itamar Levi of Bar-Ilan University have released a new research paper titled "Privacy with Leakage from Falsifiable Assumptions." Published as Paper 2026\/2551 on the Cryptology ePrint Archive, the work introduces a novel approach to evaluating the privacy of cryptographic schemes under side-channel attacks. By replacing complex simulatability requirements with a direct, practically falsifiable security experiment, the authors provide the first privacy proof for encryption schemes\u2014such as the well-known PSV scheme\u2014that relies strictly on falsifiable assumptions without necessitating the traditional, costly premise that a protected component is entirely leak-free.<\/p>\n
To understand the significance of Berti and Levi\u2019s contribution, one must look at how modern cryptography establishes trust. An inherent challenge across the discipline is finding models and assumptions that are both realistic and meaningful. Crucially, foundational security assumptions must be falsifiable\u2014meaning there must be a well-defined, practical way to test and potentially disprove them. <\/p>\n
For symmetric-key cryptography operating in the standard model, where adversaries interact with systems only through black-box inputs and outputs without extracting physical leakage, the cryptographic community largely agrees that the right assumptions have been identified. These are anchored in pseudorandom functions (PRFs) and pseudorandom permutations (PRPs), which serve as the bedrock for modern symmetric encryption, message authentication codes, and related primitives.<\/p>\n
However, the landscape shifts dramatically when moving from the abstract standard model to the physical world of side-channel attacks (SCAs). Side-channel attacks exploit physical emissions from electronic systems\u2014such as power consumption, electromagnetic radiation, or acoustic emanations\u2014during cryptographic computations. In this leakage-aware setting, designing secure systems becomes significantly more complex, and the traditional requirements for ensuring data integrity and privacy diverge.<\/p>\n
When evaluating data integrity in the presence of side-channel leakage, cryptographic engineering has made substantial theoretical and practical progress. Thanks to advances in what researchers call the unbounded leakage model, achieving robust integrity has become relatively straightforward. Under this model, it is sufficient to claim and prove integrity based exclusively on black-box properties by carefully instantiating a single strongly unpredictable-with-leakage primitive, such as a tweakable block cipher.<\/p>\n
Privacy, on the other hand, has proven to be a much more stubborn problem. For a system to maintain privacy against side-channel analysis, unauthorized observers must not be able to deduce the secret key or plaintext from the physical traces emitted by the device. To formalize this requirement, cryptographers previously turned to the concept of simulatability.<\/p>\n
Originally proposed by Yu and Standaert at CRYPTO 2013, the simulatability approach dictates that a cryptographic scheme is private if an independent simulator can accurately mimic the physical leakage traces of the hardware device without having access to the underlying secret key. If a simulator can generate traces that are computationally indistinguishable from real physical executions, the system is deemed secure. <\/p>\n
While elegant in theory, simulatability has encountered severe roadblocks in practice. Simulating the complex physical behavior of modern electronic systems\u2014complete with noise, non-linear power profiles, and intricate hardware-software interactions\u2014and rigorously arguing that distinguishing simulation from reality is computationally hard has proven to be an exceptionally difficult task. Prominent cryptographic works, such as those by Galea et al. at ASIACRYPT 2014 and more recently by Deperz et al. at Cascade 2026, have highlighted the immense barriers and fragility associated with proving simulatability for complex hardware implementations.<\/p>\n
Seeking a way out of the simulatability dilemma, Berti and Levi propose a new model and a distinct set of security assumptions in their 2026 paper. Rather than attempting to model and simulate entire physical systems, the researchers isolate a single, critical component of leakage-resilient cryptography: the key-refreshing process.<\/p>\n
The key-refreshing process is a mechanism used in side-channel countermeasures where secret keys are periodically updated or randomized to prevent attackers from accumulating enough physical leakage to mount a successful differential power analysis or related attack. Berti and Levi formulate a rigorous security definition for this isolated process, which they term "secure refreshing."<\/p>\n
Crucially, like simulatability, this new assumption is designed to capture the security of the key-refreshing process. However, instead of relying on an abstract simulator whose accuracy is notoriously difficult to verify, the authors formalize security through a direct refreshing experiment. This experiment is structured so that it can be practically falsified by evaluation laboratories. By grounding the security definition in an experiment that labs can actually run, test, and potentially disprove, the approach avoids many of the concrete problems and conceptual vulnerabilities that have plagued previous simulation-based models.<\/p>\n
Building upon this foundational model, and aiming to provide an additional layer of security assurance for strongly SCA-protected leak-free components, the researchers introduce a second concept: strongly protected secure refreshing. <\/p>\n
To demonstrate the real-world utility of their new framework, Berti and Levi apply their assumptions to a concrete cryptographic construction. Using their newly introduced models, they successfully prove the privacy of the well-known PSV encryption scheme.<\/p>\n
This result marks a notable milestone in side-channel cryptography. It provides the first-ever privacy proof for the scheme that relies exclusively on falsifiable assumptions. More importantly, the proof achieves this without assuming that the strongly protected component of the hardware is entirely leak-free\u2014an idealized and often unrealistic assumption that has long been a point of contention in hardware security evaluations.<\/p>\n
In practical terms, dropping the strict requirement for a perfectly leak-free component can translate to significant computational and implementation cost reductions. Hardware designers are frequently forced to implement excessive, power-hungry, and silicon-expensive countermeasures to ensure that a core component meets the theoretical standard of being completely leak-free. By demonstrating that robust privacy can be proven under realistic, falsifiable assumptions even when minor leakage is permitted in protected regions, Berti and Levi\u2019s work opens the door to more efficient, cost-effective, and verifiable cryptographic hardware designs.<\/p>\n
The complete research paper, along with formal definitions, proofs, and associated BibTeX references for academic citation, is publicly available on the Cryptology ePrint Archive under paper identifier 2026\/2551, providing researchers and evaluation laboratories with the mathematical framework needed to begin testing and implementing these new standards.<\/p>\n","protected":false},"excerpt":{"rendered":"
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