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We know unlike ecrecover, it is impossible to get to public key given schnorr signature = (r,s) since rG = sG-eP . So, would like to understand what are the security risks,

if we say signature=F(r,s,e)

and get to publicKey at the verification? something like this P = (rG-sG)/e

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There are no security risks to this since e is public anyway. Depending on how you are using it you probably want to make sure that e is consistent with R afterwards i.e. recompute e from P and R and m to make sure it is correct. However, it makes more sense to me to just include P directly instead of e.

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  • Okay, thank you @LLFourn. But my point/question is to derive publicKey from signature. Mar 30, 2022 at 16:44
  • But it's the same amount of data to just include P. Why can't extracting the trailing 32 bytes count as deriving?
    – LLFourn
    Apr 1, 2022 at 4:52

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