Protecting smart cards from power analysis with detachable power supplies
First Claim
1. A method of protecting a smart card including a smart card chip which performs computation from cryptanalytic attacks based on power analysis, in which during at least part of computation being performed, furnishing power to the smart card chip from a discharging capacitor contained in the smart card, and during some different part of the computation being performed, charging the capacitor from an external power supply.
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Accused Products
Abstract
A method and apparatus for protecting smart cards against simple and differential power attacks when they are inserted into card readers controlled by other entities. The technique is particularly useful in financial applications such as ATM cards, credit cards, and electronic wallets, in which cards have to be inserted into card readers which may be specifically manufactured or modified to perform undetectable measurements of the power supplied to the card during its normal operation. The basic technique is to use two capacitors embedded in the smart card in such a way that at any given time one of them is charged by the external power supply and the other one is discharged by powering the smart card chip. The roles of the two capacitors alternate rapidly, and the power supply is detached from the smart card chip in the sense that external power measurements do not reveal information about its internal operations.
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Citations
27 Claims
- 1. A method of protecting a smart card including a smart card chip which performs computation from cryptanalytic attacks based on power analysis, in which during at least part of computation being performed, furnishing power to the smart card chip from a discharging capacitor contained in the smart card, and during some different part of the computation being performed, charging the capacitor from an external power supply.
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11. A method comprising the steps of:
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a) powering a smart card including a chip for performing computations by a discharging capacitor connected to the chip while it is performing at least part of its computations, b) changing the connections to the capacitor to disconnect it from the chip and enable its charging, and c) charging the capacitor while it is disconnected from the chip. - View Dependent Claims (12, 13, 14, 15)
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16. Apparatus comprising:
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a) a smart card containing a smart card chip for performing calculations, b) a capacitor, c) contacts for connecting an external power supply to the capacitor, and d) switchover logic for alternately connecting the capacitor to power the smart card chip and to be charged by the external power supply. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification