Non-Linear LDO Cascades for Crypto Side-Channel Suppression
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Solution Overview
Problem
Conventional power regulator-based techniques provide insufficient resistance against side-channel attacks in the frequency-domain, as they induce linear transformations that can be easily exposed through methods like fast Fourier transform, failing to effectively boost the minimum traces to disclose (MTD) in cryptographic devices.
Innovation Solution
A cascaded implementation of a non-linear low-dropout regulator (NL-LDO) and cryptographic engines augmented with arithmetic transformations, which randomizes control loop parameters and provides a wide-dynamic-range, high-bandwidth response to mask power consumption variations, achieving significant boosts in both time and frequency-domain MTD with minimal area overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If linear transformations are used in power regulators, then device complexity is reduced, but frequency-domain security deteriorates
Solution Approach 1:
The patent modifies the regulator's transfer function parameter from linear to non-linear, creating a system where the relationship between input and output power changes dynamically with operating conditions. This non-linear parameter change maintains relative device simplicity while dramatically improving frequency-domain security against side-channel attacks.
2Measurement precision
If non-linear LDO with arithmetic transformations is implemented, then frequency-domain MTD is improved, but device complexity increases
Solution Approach 1:
The patent merges the non-linear LDO power regulator with cryptographic arithmetic transformation blocks into an integrated circuit. This consolidation achieves frequency-domain MTD improvement through non-linear transformations while managing device complexity by integrating multiple functions into a unified structure rather than adding separate components.
Solution Approach 2:
The integrated circuit performs multiple functions: power regulation, cryptographic operations, and non-linear transformations for side-channel protection. This multi-functionality reduces overall system complexity by combining what would otherwise be separate components into a single universal block that handles all these tasks.
Data Source
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AI summary
Apparatus and method for resisting side-channel attacks on cryptographic engines are described herein. An apparatus embodiment includes a cryptographic block coupled to a non-linear low-dropout voltage regulator (NL-LDO). The NL-LDO includes a scalable power train to provide a variable load current to the cryptographic block, randomization circuitry to generate randomized values for setting a plurality of parameters, and a controller to adjust the variable load current provided to the cryptographic block based on the parameters and the current voltage of the cryptographic block. The controller to cause a decrease in the variable load current when the current voltage is above a high voltage threshold, an increase in the variable load current when the current voltage is below a low voltage threshold; and a maximization of the variable load current when the current voltage is below an undervoltage threshold. The cryptographic block may be implemented with arithmetic transformations.