Swift package with elliptic curve public key cryptography, ECDSA, Schnorr Signatures for Bitcoin and C bindings from libsecp256k1.
Long-term goals are:
- Lightweight ECDSA & Schnorr Signatures functionality
- Built for simple or advance usage with things like BIP340
- Exposed C bindings to take full control of the secp256k1 implementation
- Familiar API design by modeling after Swift Crypto
- Automatic updates for Swift and libsecp256k1
- Availability for Linux and Apple platform ecosystems
This repository primarily uses Swift package manager as its build tool, so we recommend using that as well. Xcode comes with built-in support for Swift packages. From the menu bar, goto: File > Add Packages... If you manage packages via a Package.swift file, simply add secp256k1.swift as a dependencies' clause in your Swift manifest:
.package(name: "secp256k1.swift", url: "https://github.com/GigaBitcoin/secp256k1.swift.git", exact: "0.15.0"),Include secp256k1 as a dependency for your executable target:
.target(name: "<target>", dependencies: [
.product(name: "secp256k1", package: "secp256k1.swift")
]),Try in a playground using the SPI Playgrounds app or 🏟 Arena
arena GigaBitcoin/secp256k1.swiftimport secp256k1
// Private key
let privateBytes = try! "14E4A74438858920D8A35FB2D88677580B6A2EE9BE4E711AE34EC6B396D87B5C".bytes
let privateKey = try! secp256k1.Signing.PrivateKey(rawRepresentation: privateBytes)
// Public key
print(String(bytes: privateKey.publicKey.rawRepresentation))
// ECDSA
let messageData = "We're all Satoshi.".data(using: .utf8)!
let signature = try! privateKey.signature(for: messageData)
// DER signature
print(try! signature.derRepresentation.base64EncodedString())// Strict BIP340 mode is disabled by default for Schnorr signatures with variable length messages
let privateKey = try! secp256k1.Schnorr.PrivateKey()
// Extra params for custom signing
var auxRand = try! "C87AA53824B4D7AE2EB035A2B5BBBCCC080E76CDC6D1692C4B0B62D798E6D906".bytes
var messageDigest = try! "7E2D58D8B3BCDF1ABADEC7829054F90DDA9805AAB56C77333024B9D0A508B75C".bytes
// API allows for signing variable length messages
let signature = try! privateKey.signature(message: &messageDigest, auxiliaryRand: &auxRand)let privateKey = try! secp256k1.Signing.PrivateKey()
// Adding a tweak to the private key and public key
let tweak = try! "5f0da318c6e02f653a789950e55756ade9f194e1ec228d7f368de1bd821322b6".bytes
let tweakedPrivateKey = try! privateKey.add(tweak)
let tweakedPublicKeyKey = try! privateKey.publicKey.add(tweak)let privateKey = try! secp256k1.KeyAgreement.PrivateKey()
let publicKey = try! secp256k1.KeyAgreement.PrivateKey().publicKey
// Create a compressed shared secret with a private key from only a public key
let sharedSecret = try! privateKey.sharedSecretFromKeyAgreement(with: publicKey, format: .compressed)
// By default, libsecp256k1 hashes the x-coordinate with version information.
let symmetricKey = SHA256.hash(data: sharedSecret.bytes)let privateSign1 = try! secp256k1.Signing.PrivateKey()
let privateSign2 = try! secp256k1.Signing.PrivateKey()
let privateKey1 = try! secp256k1.KeyAgreement.PrivateKey(rawRepresentation: privateSign1.rawRepresentation)
let privateKey2 = try! secp256k1.KeyAgreement.PrivateKey(rawRepresentation: privateSign2.rawRepresentation)
let sharedSecret1 = try! privateKey1.sharedSecretFromKeyAgreement(with: privateKey2.publicKey)
let sharedSecret2 = try! privateKey2.sharedSecretFromKeyAgreement(with: privateKey1.publicKey)
let sharedSecretSign1 = try! secp256k1.Signing.PrivateKey(rawRepresentation: sharedSecret1.bytes)
let sharedSecretSign2 = try! secp256k1.Signing.PrivateKey(rawRepresentation: sharedSecret2.bytes)
// Payable Silent Payment public key
let xonlyTweak2 = try! sharedSecretSign2.publicKey.xonly.add(privateSign1.publicKey.xonly.bytes)
// Spendable Silent Payment private key
let privateTweak1 = try! sharedSecretSign1.add(xonly: privateSign1.publicKey.xonly.bytes)let privateKey = try! secp256k1.Recovery.PrivateKey()
let messageData = "We're all Satoshi.".data(using: .utf8)!
// Create a recoverable ECDSA signature
let recoverySignature = try! privateKey.signature(for: messageData)
// Recover an ECDSA public key from a signature
let publicKey = try! secp256k1.Recovery.PublicKey(messageData, signature: recoverySignature)
// Convert a recoverable signature into a normal signature
let signature = try! recoverySignature.normalizelet privateKey = try! secp256k1.Signing.PrivateKey()
let publicKey = try! secp256k1.Signing.PrivateKey().public
// The Combine API arguments are an array of PublicKey objects and an optional format
publicKey.combine([privateKey.publicKey], format: .uncompressed)let privateKeyString = """
-----BEGIN EC PRIVATE KEY-----
MHQCAQEEIBXwHPDpec6b07GeLbnwetT0dvWzp0nV3MR+4pPKXIc7oAcGBSuBBAAK
oUQDQgAEt2uDn+2GqqYs/fmkBr5+rCQ3oiFSIJMAcjHIrTDS6HEELgguOatmFBOp
2wU4P2TAl/0Ihiq+nMkrAIV69m2W8g==
-----END EC PRIVATE KEY-----
"""
// Import keys generated from OpenSSL
let privateKey = try! secp256k1.Signing.PrivateKey(pemRepresentation: privateKeyString)These APIs should not be considered stable and may change at any time.