Fix: append final carry after wnaf_form loop#83
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Summary
Fixes
wnaf_formdropping a final carry after processing the last input bit.For window size
w, a negative digit setscarry = 1. If that carry remains afterpos >= bit_len, the previous code terminates without emitting it, so the produced WNAF digits reconstructed a different scalar.For example, with
window = 4,[0xff]encoded as[-1, 0, 0, 0, 0, 0, 0, 0], which evaluates to-1instead of255.This appends the final carry when present and adds a regression test for
[0xff], whose correct WNAF is[-1, 0, 0, 0, 0, 0, 0, 0, 1].Test
cargo test wnaf_form_keeps_final_carry