Anais - Engenharia de Redes de Comunicação - UnB

• This configuration is not possible.
STEP 3: Determination of the bits on the left side of the central column.
Assume the following notation.
(
α β
δ x
)
=
(
a
t−1
i−1
a t i−1
a t−1
i
x
)
One can easily see that there are 8 different possibilities for the bits {α, β, δ}. Basing
on equation 1, an adversary in possession of the bits {α, β, δ} can determine the bit a t−1
i−2
without applying any fault into the register.
We shall now analyze these 8 possibilities.
Configuration 3.1
(
a
t−1
i−2
a t−1
i−1
a t−1
i
x a t i−1 x
)
=
(
a
t−1
i−2 0 0
x 0 x
)
• This configuration is only possible for a t−1
i−2 = 0.
Configuration 3.2
(
a
t−1
i−2
a t−1
i−1
a t−1
i
x a t i−1 x
)
=
(
a
t−1
i−2 0 0
x 1 x
)
• This configuration is only possible for a t−1
i−2 = 1.
Configuration 3.3
(
a
t−1
i−2
a t−1
i−1
a t−1
i
x a t i−1 x
)
=
(
a
t−1
i−2 1 0
x 0 x
)
• This configuration is only possible for a t−1
i−2 = 1 .
Configuration 3.4
(
a
t−1
i−2
a t−1
i−1
a t−1
i
x a t i−1 x
)
=
(
a
t−1
i−2 1 0
x 1 x
)
• This configuration is only possible for a t−1
i−2 = 0.
Configuration 3.5
(
a
t−1
i−2
a t−1
i−1
a t−1
i
x a t i−1 x
)
=
(
a
t−1
i−2 0 1
x 0 x
)
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