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<P><JC><B>Introduction to Differential Power Analysis and Related Attacks</B>
<P><JC>By: By Paul Kocher, Joshua Jaffe, and Benjamin Jun
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<P>As part of Cryptography Research's ongoing cryptosystem research activities, we have been analyzing how to improve security of portable cryptographic tokens, including smart cards. Over the past year and a half, we have been working with the smart card vendor community to address attacks we have developed including Simple Power Analysis, Differential Power Analysis, High-Order Differential Power Analysis, and other related techniques. These are technically sophisticated and extremely powerful analysis tools that can be used by a cryptanalyist to extract secret keys from cryptographic devices. 
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<P>These are not theoretical attacks. Cryptography Research has successfully used these attacks to analyze a large number of smart card products. While some products can withstand simple power analysis, we have not found any commercially-available products that resist DPA. (It is expected that a few systems currently being engineered using techniques licensed by Cryptography Research will be resistant to power analysis attacks.)
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<P>These analysis techniques are of considerable concern, since the attacks can be mounted quickly and can be implemented using readily-available hardware costing only a few hundred to a few thousand dollars. The amount of time required for the attack and analysis depends on the type of attack (DPA, SPA, etc.) and varies somewhat by device. SPA attacks typically take a few seconds per card, while DPA attacks can take several hours.