Analysis of the C library's schnorrsig_sign showed three key differences:
1. C takes a pre-computed keypair (no pubkey derivation during signing)
2. C does NOT self-verify the signature after signing
3. C does 1 EC multiplication total; we were doing 3
Changes:
- signSchnorrInternal: extracted core signing logic without pubkey derivation
or self-verification. Does exactly 1 mulG (for R = k·G) matching the C library.
- signSchnorr: convenience overload that derives pubkey then calls internal.
Now ~2x faster since self-verify is removed.
- signSchnorrWithPubKey: fast path accepting a 33-byte compressed pubkey
(includes y-parity in the 02/03 prefix). Skips the pubkey G multiplication
entirely. ~4.8x faster than the previous signSchnorr.
- Secp256k1Instance: added signSchnorrWithPubKey forwarding method.
- Benchmark: added "signSchnorr (cached pk)" test comparing both paths.
The self-verify removal is safe: the BIP-340 test vectors (which include
the exact expected signatures) validate correctness, and the C reference
library does not self-verify either.
Benchmark:
signSchnorr: 1,516 → 2,915 ops/s (1.9x faster, 17x → 9.5x)
signSchnorr (cached pk): N/A → 7,261 ops/s (3.9x vs native — new!)
https://claude.ai/code/session_01BhU63WUe9AhikZxRdw3Lpg
Claude
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