Cryptography Reference
In-Depth Information
Fig. 2.
References dispersion for different number of traces: (1.a) 100 traces,(1.b) 1000
traces, (1.c) 10000 traces, (1.d) 81000 traces
represents a global description of the leakage without the need of more detailed
knowledge about the encryption process. The idea is that, if the key guess is
correct, PCA applied to the different partitions should be able to explain a big
proportion of the variance with only a few components. On the opposite, if the
key guess is wrong, the power traces are sorted randomly, and PCA will need
more components to explain the same proportion of variance. Thus, a reduced
form of the indicator
F
k
j
is deduced from equation (2) and defined as follows:
m
Red F
CS
k
j
=
(
λ
m
)
.
m
=1
This indicator can be used for Dual rail Precharge Logic (DPL) architectures,
like WDDL [10], which aim at making the activity of the cryptographic process
constant independently from the manipulated data. Statistically, the idea behind
DPL is to force all references to have the same statistic and probabilistic fea-
tures, for all made partitions. However, in the real life application, an ideal DPL
implementation could not exist. In that sense, the reduced indicator
Red F
CS
k
j
can exploit the leaked information without the knowledge of the position factor.
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