Update reference code and test vectors

[jonasnick]

Probably not final because we may want to make synthetic nonces the default (bitcoin#886) and change where to put the additional randomness (#195).

[jonasnick]

Should be up to date now with #199. I'm cross-checking the test vectors with the libsecp implementation.

[jonasnick]

Test vectors pass in my (locally) updated libsecp schnorrsig branch. Pr is ready for review.

[elichai]

FWIW the "int-wise" and "byte-wise" xor should be equivalent, so if they're both ints you can just do seckey ^ aux_rand.
This also applies to the "Default signing" protocol ie Let t be the byte-wise xor of bytes(d) and HBIP340/aux(a)[12].

[sipa]

Sure, but seckey is a byte array, not an integer in the BIP, and we haven't defined an xor operation for either. You could write it as convert to int, xor, and convert back to bytes... but that would be very far removed from how things get implemented in non-prototyping code.

[elichai]

Sure, but seckey is a byte array, not an integer in the BIP, and we haven't defined an xor operation for either. You could write it as convert to int, xor, and convert back to bytes... but that would be very far removed from how things get implemented in non-prototyping code.

Yeah, in any non-python enviroment you'll obviously do it by bytes. I was just confused a bit because of the wording "be the byte-wise xor", it made me think for a second that that's a distinct thing.

[sipa]

ACK

[real-or-random]

ACK except nit

[real-or-random]

Suggested change

	# For historic reasons (pubkey tiebreaker was squareness and not evenness)
	# For historical reasons (pubkey tiebreaker was squareness and not evenness)

[real-or-random]

@sipa Feel free to merge, I can fix the nit in my PR.