Breaking Trivium Stream Cipher Implemented in ASIC Using Experimental Attacks and DFA

. 2020 Dec 3;20(23):6909. doi: 10.3390/s20236909

Algorithm 2: Backward Trivium.

Require: Number of clock cycles $n = 1153 + X + t_{800}$ .
for $i = {1}$ do
if $S_{93} = S_{66} ⨁ S_{171} ⨁ S_{91} \cdot S_{92}$ then
$S_{92}^{'} \leftarrow 1$ else $S_{92}^{'} \leftarrow 0$
end if
if $S_{177} = S_{162} ⨁ S_{264} ⨁ S_{175} \cdot S_{176}$ then
$S_{176}^{'} \leftarrow 1$ else $S_{176}^{'} \leftarrow 0$
end if
if $S_{0} = S_{243} ⨁ S_{69} ⨁ S_{286} \cdot S_{287}$ then
$S_{287}^{'} \leftarrow 1$ else $S_{287}^{'} \leftarrow 0$
end if
$(S_{0}, S_{1}, \dots, S_{92}) \leftarrow (S_{1}, S_{92}, \dots, S_{92}^{'})$
$(S_{93}, S_{94}, \dots, S_{176}) \leftarrow (S_{94}, S_{176}, \dots, S_{176}^{'})$
$(S_{177}, S_{178}, \dots, S_{287}) \leftarrow (S_{178}, S_{287}, \dots, S_{287}^{'})$
end for