What should we do if s in the ecdsa signature is greater than n/2? As we all know, in the ECDSA signature of Ethernum, the output s must be smaller than n/2, where s is the signature output and n is the ECC group order. If s>n/2, we have two choices:
- Should we just re-choose a k, then re-sign the message to make s
- Or just make $v\oplus 1$ in the signature to make r -> (x,-y)?
What Ethernum ECDSA really do?