LoRa-Based Physical Layer Key Generation for Secure V2V/V2I Communications

. 2020 Jan 26;20(3):682. doi: 10.3390/s20030682

Algorithm 2: Level-crossing algorithm.

Require:

{\hat{\underline{h}}}_{a}

and

{\hat{\underline{h}}}_{b}

Ensure: Alice and Bob’s

K_{a}

and

K_{b}

Alice:

for $i = 1$ $t o$ $l e n g t h ({\hat{\underline{h}}}_{a}) - m$ do
if $Q ({\hat{h}}_{a} [i]) = Q ({\hat{h}}_{a} [i + 1]) \dots = Q (({\hat{h}}_{a} [i + m - 1]))$ then
$i_{e n d} \leftarrow l a s t i n d e x i n e x c u r s i o n$
$L^{'} \leftarrow [L^{'}; ⌊\frac{i + i_{e n d}}{2}⌋]$
$i \leftarrow i_{e n d} + 1$
else
$i \leftarrow i + 1$
end if
end for
$L = R a n d o m s u b s e t o f L^{'}$
Alice send L to Bob PUBLIC_CHANNEL

Bob:

for $l \in L$ do
if $Q ({\hat{h}}_{b} [l - ⌊\frac{m - 2}{2}⌋]) = \dots = Q ({\hat{h}}_{b} [l + ⌈\frac{m - 2}{2}⌉])$ then
$\tilde{L} \leftarrow [\tilde{L}; l]$
end if
end for
$K_{b} = Q ({\hat{h}}_{b} (\tilde{L}))$
Bob send $\tilde{L}$ to Alice on PUBLIC_CHANNEL

Alice:

K_{a} = Q ({\hat{h}}_{a} (\tilde{L}))