> Op 6 jul. 2018, om 20:08 heeft Pieter Wuille via bitcoin-dev 
> <bitcoin-dev@lists.linuxfoundation.org> het volgende geschreven:
> 
> Hello everyone,
> 
> Here is a proposed BIP for 64-byte elliptic curve Schnorr signatures,
> over the same curve as is currently used in ECDSA:
> https://github.com/sipa/bips/blob/bip-schnorr/bip-schnorr.mediawiki

The power of simplification at work, thanks Pieter!

Questions:

Regarding verification: why does bytes(P) use compressed key serialization 
rather than the implicit Y coordinate used for signing? I understand space 
savings don't matter since these values don't end up on the blockchain. Is it 
just easier to implement or is it faster?

Regarding rationale for choosing (e,s) vs. (R,s), you say that (e,s) "avoids 
the difficulty of encoding a point R in the signature". But since e = H(sG - eP 
|| m) also involves converting a point to some byte encoding in order to hash 
it, how much difficulty is actually avoided? Is that, like for previous 
question, because you could get away with compressed keys rather than implicit 
Y coordinates?

Regarding batch verification: "randomly generated independently for each batch 
of verifications" - by whom? I assume randomly picked by the verifier?

Regarding random number used for signing. The suggested (?) deterministic 
algorithm to derive secret key ''k'' from the private key ''d''  seems similar 
to RFC6979. Maybe it's useful to briefly explain the difference, as well as 
your rationale for not making it mandatory (presumably the same as why RFC6979 
isn't mandatory although most (?) wallets use it).

Nits:

* Motivation: "signatures ... These are standardized", but the "standardized" 
link points to the secp256k1 curve parameters, not to anything signature 
related afaik
* "message m: an array of 32 bytes", maybe add "typically the sha256 hash of 
the transaction components commited to by SIGHASH_TYPE”
* I left a few even smaller nits as a PR: https://github.com/sipa/bips/pull/10

Cheers,

Sjors

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