P256K.Format

Compressed (33-byte) and uncompressed (65-byte) serialization formats for secp256k1 public keys, passed as flags to secp256k1_ec_pubkey_serialize.

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

enum Format

Mentioned In

Working with Keys

Overview

Use P256K.Format.compressed for standard secp256k1 key storage and transmission in Bitcoin and Nostr contexts — this has been the default since Bitcoin Core 0.6 (2012) and saves 32 bytes per key on the wire. Use P256K.Format.uncompressed when interoperating with systems that require the full (x, y) curve point, including legacy Bitcoin addresses, some OpenSSL wire formats, and non-Bitcoin ECDSA consumers that have not adopted the point-compression optimization.

Schnorr / BIP-340 / Taproot workflows use a third representation (x-only, 32 bytes) which is modeled separately via P256K.Schnorr.XonlyKey and is not a Format case.

Topics

Cases

Serialization Details

var length: Int
The serialized byte length of the public key: 33 bytes for P256K.Format.compressed, 65 bytes for P256K.Format.uncompressed.
var rawValue: UInt32
The secp256k1_ec_pubkey_serialize format flag: SECP256K1_EC_COMPRESSED for P256K.Format.compressed, SECP256K1_EC_UNCOMPRESSED for P256K.Format.uncompressed.

Initializers

init?(rawValue: UInt32)