Switched-Capacitor Charge Withholding for DPA Security
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing countermeasures against differential power analysis (DPA) attacks consume significant dynamic power to hide or mask load power information, and can be neutralized by machine-learning-based attacks that synchronize with the switching frequency of on-chip voltage converters.
Innovation Solution
The charge-withheld converter-reshuffling technique uses pseudorandom number generators to control the charging and discharging of switched capacitor stages, withholding a random amount of charge for a random time period, thereby decorrelating input and output power and preventing accurate load power information acquisition even if the attacker synchronizes with the sampling frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If converter-reshuffling technique is used to randomly reshuffle converter stages, then power efficiency is improved and noise is inserted to prevent DPA attacks, but the total number of activated phases still correlates with dynamic power consumption allowing ML-based attacks to succeed
Solution Approach 1:
The patent applies preliminary action by pre-charging flying capacitors in converter stages before the actual power conversion operation. This pre-charging phase stores energy in the capacitors, which is then released during the conversion process. By separating the charging action from the conversion action and introducing random delays, the patent decouples the correlation between activated phases and instantaneous power consumption, preventing attackers from inferring workload information from power traces.
Solution Approach 2:
The patent implements dynamics by introducing random time delays in the activation of converter stages. Instead of a fixed deterministic sequence, the activation timing becomes dynamic and unpredictable. The system randomly selects which stages to activate and when to activate them, creating a dynamic power consumption profile that does not directly correlate with the computational workload, thereby securing against DPA attacks while maintaining power efficiency.
2Measurement precision
If machine-learning attacks synchronize with switching frequency, then attacker can unscramble power data and neutralize CoRe technique, but this requires precise frequency matching and timing synchronization
Solution Approach 1:
The patent applies preliminary action by pre-charging flying capacitors in converter stages before the actual power conversion operation. This pre-charging phase stores energy in the capacitors, which is then released during the conversion process. By separating the charging action from the conversion action and introducing random delays, the patent decouples the correlation between activated phases and instantaneous power consumption, preventing attackers from inferring workload information from power traces.
Solution Approach 2:
The patent implements dynamics by introducing random time delays in the activation of converter stages. Instead of a fixed deterministic sequence, the activation timing becomes dynamic and unpredictable. The system randomly selects which stages to activate and when to activate them, creating a dynamic power consumption profile that does not directly correlate with the computational workload, thereby securing against DPA attacks while maintaining power efficiency.
3Reliability
If charge is withheld for random time period, then power trace entropy increases by 46.1% and zero power trace entropy is eliminated, but additional control complexity is introduced
Solution Approach 1:
The patent applies segmentation by dividing the converter system into multiple independent stages, each with its own flying capacitor that can be charged and discharged independently. The charging controller segments the control logic into separate charging and discharging control units, each managing specific stages. This segmentation allows the system to withhold charge in a distributed manner across multiple stages, increasing power trace entropy while keeping individual controller units relatively simple and manageable.
Data Source
AI summary
Methods and systems are provided for a charge withholding converter reshuffling technique that decorrelates input power of a multi-phase switched capacitor (SC) voltage converter relative to the output power provided to a load. The load may be a cryptographic device. The technique provides a countermeasure against power analysis attacks. A controller including a first random number generator coupled to the stages of the SC voltage converter controls gating for charging a first subset of the stages. A controller including a second random number generator coupled the stages of the SC voltage converter controls gating for discharging a second subset the stages. A number of the switched capacitor stages maintain their charge beyond the switch period in which they are charged. The SC voltage converter withholds a random portion of input charge and delivers this charge to the load after a random time period.