Instance Method

add(_:format:)

Creates a new P256K.Signing.PublicKey by computing public_key' = public_key + G × tweak via secp256k1_ec_pubkey_tweak_add, where G is the secp256k1 generator point.

iOS 13.0+
macCatalyst 13.0+
macOS 10.15+
tvOS 13.0+
visionOS 1.0+
watchOS 6.0+

func add(_ tweak: [UInt8], format: P256K.Format = .compressed) throws -> P256K.Signing.PublicKey

Parameters

tweak: A 32-byte tweak scalar; must not produce the point at infinity.
format: The serialization format of the returned P256K.Signing.PublicKey; defaults to .compressed.

Return Value

A new P256K.Signing.PublicKey equal to the original key plus the tweak times the generator.

Discussion

The public-key counterpart to add(_:) — applying the same 32-byte tweak to both forms yields a valid (sk', pk') pair. Used by BIP-32 unhardened public-key-only derivation (watch-only wallets) when the parent private key is not available.

Throws

secp256k1Error.underlyingCryptoError if the tweak is invalid or the result is the point at infinity.