Round Reduction Using Faults

Abstract

This paper presents a practical implementation of a fault attack implemented on a Silvercard (a freely available smart card based on a PIC16F877 produced by Microchip). The aim of the fault attack is to effectively reduce the number of rounds of a secret key algorithm. The simplest case of reducing the number of rounds to one was chosen to facilitate subsequent cryptanalysis. The fault injection method used is a glitch on the power supplied to the smart card. The manner in which this changes the functioning of the smart card is described, followed by how this effect can then be used to produce the desired result. A description of how this was applied to an AES implementation is given. Lastly, Various generic countermeasures are discussed to show how this type of attack can be prevented.