Perf: optimize BLS24-317 final exp #356
Merged
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The seed
x
of BLS24-317 is even. Givenz ∈ Fp24
, we can re-usez^2
to computez^x
(Expt) by having a function that computesz^(x/2)
(ExptHalf). This saves the last cyclotomic square. Also, there are 4 Expt in a row in the hard part which we can compute using 4 ExptHalf and then do 4 Karabina cyclotomic squares (instead of Granger-Scott) with a single decompression (inverse).