This commit introduces a new `ecmultWindowedVar` function that implements optimized windowed multiplication for scalar multiplication, significantly improving performance during verification operations. The existing `Ecmult` function is updated to utilize this new implementation, converting points to affine coordinates for efficiency. Additionally, the `EcmultConst` function is retained for constant-time operations. The changes also include enhancements to the generator multiplication context, utilizing precomputed byte points for improved efficiency. Overall, these optimizations lead to a notable reduction in operation times for cryptographic computations.
This commit introduces the implementation of Schnorr signatures following BIP-340, including the `SchnorrSign` and `SchnorrVerify` functions. It also adds comprehensive tests to validate the signing and verification processes, ensuring correct functionality with both standard and auxiliary randomness. The tests cover various scenarios, including signature generation, verification, and edge cases, enhancing the robustness of the secp256k1 implementation. Additionally, new files for Schnorr signature operations and tests have been created, contributing to the overall cryptographic capabilities of the library.
