Patent ID: 9544132
Date: 2017-01-10
CPC Classifications: G06F,H04L

Claim:
1. A method to protect a key hardware register against fault attack, this register being inside a hardware block cipher BC embedded inside an electronic component, said component containing, stored inside a memory area, a cryptographic key Kram, the method comprises: A. loading the key Kram inside said register, B. determining a value X wherein the value X is uniquely defined such that application of the block cipher to the value X using the key K, the resulting cipher text has exactly a value equal to the key K, i.e., K=BC(K,X), wherein key K is the key Kram loaded inside said register, C. after at least one sensitive operation, computing a value V such as V=BC(K,X), D. comparing the value V with the key Kram value stored in the memory area, E. if the value V is not equal to the key Kram, raising an error that a fault has occurred.