Swift cryptography library for Bitcoin and Nostr. ECDSA, Schnorr Signatures, Elliptic Curve Diffie-Hellman, and zero-knowledge proofs. Uses Swift's C interoperability with libsecp256k1.
🌐 Project page · 📚 Documentation
- Provide lightweight ECDSA & Schnorr Signatures functionality
- Support simple and advanced usage, including BIP-327 and BIP-340
- Expose libsecp256k1 bindings for full control of the implementation
- Offer a familiar API design inspired by Swift Crypto
- Maintain automatic updates for Swift and libsecp256k1
- Ensure availability for Linux and Apple platform ecosystems
This package uses Swift Package Manager. To add it to your project:
- Go to
File > Add Packages... - Enter the package URL:
https://github.com/21-DOT-DEV/swift-secp256k1 - Select the desired version
Add the following to your Package.swift file:
.package(url: "https://github.com/21-DOT-DEV/swift-secp256k1", from: "0.23.0"),Warning
This package is pre-1.0 (SemVer major version zero). The public API should not be considered stable and may change with any release. Pin a version using exact: to avoid unexpected breaking changes.
Then, include P256K as a dependency in your target:
.target(name: "<target>", dependencies: [
.product(name: "P256K", package: "swift-secp256k1")
]),Using CocoaPods (version history)
Add the following to your Podfile:
pod 'swift-secp256k1', '0.23.0'Note
Swift Package Manager is the recommended way to add this package. CocoaPods support may be deprecated in a future release.
Use Arena to try the package in a playground:
arena 21-DOT-DEV/swift-secp256k1
This package uses SE-0450 Package Traits (Swift 6.1+) to enable fine-grained module selection. By default, the following traits are enabled: ecdh, musig, recovery, and schnorrsig.
To use only specific modules, specify traits in your dependency:
.package(
url: "https://github.com/21-DOT-DEV/swift-secp256k1",
from: "0.23.0",
traits: ["schnorrsig"]
),To enable all ZKP modules, use the zkp bundle trait:
.package(
url: "https://github.com/21-DOT-DEV/swift-secp256k1",
from: "0.23.0",
traits: ["zkp"]
),To use the UInt256 and Int256 fixed-width integer types, enable the uint256 trait:
.package(
url: "https://github.com/21-DOT-DEV/swift-secp256k1",
from: "0.23.0",
traits: ["uint256"]
),Note
The uint256 trait is opt-in and not enabled by default. The UInt256 and Int256 types require macOS 15, iOS 18, macCatalyst 18, watchOS 11, tvOS 18, or visionOS 2 and later.
Available traits: ecdh, ellswift, musig, recovery, schnorrsig, uint256, bppp, ecdsaAdaptor, ecdsaS2C, generator, rangeproof, schnorrsigHalfagg, surjectionproof, whitelist, zkp.
Note
Xcode does not currently resolve SwiftPM package trait conditions for Swift settings. As a workaround, all optional modules are compiled when building in Xcode. Package traits are fully supported when building with swift build from the command line.
| swift-secp256k1 | Minimum Swift Version | Minimum Xcode Version |
|---|---|---|
0.1.0 ..< 0.4.0 |
5.0 | 10.2 |
0.4.0 ..< 0.5.0 |
5.1 | 11.0 |
0.5.0 ..< 0.8.0 |
5.5 | 13.0 |
0.8.0 ..< 0.14.0 |
5.6 | 13.3 |
0.14.0 ..< 0.18.0 |
5.8 | 14.3 |
0.18.0 ..< 0.22.0 |
6.0 | 16.0 |
0.22.0 ... |
6.1 | 16.3 |
import P256K
// Private key
let privateBytes = try! "14E4A74438858920D8A35FB2D88677580B6A2EE9BE4E711AE34EC6B396D87B5C".bytes
let privateKey = try! P256K.Signing.PrivateKey(dataRepresentation: privateBytes)
// Public key
print(String(bytes: privateKey.publicKey.dataRepresentation))
// ECDSA signature
let messageData = "We're all Satoshi.".data(using: .utf8)!
let signature = privateKey.signature(for: messageData)
// DER signature
print(signature.derRepresentation.base64EncodedString())// Strict BIP340 mode is disabled by default for Schnorr signatures with variable length messages
let privateKey = try! P256K.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! P256K.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! P256K.KeyAgreement.PrivateKey()
let publicKey = try! P256K.KeyAgreement.PrivateKey().publicKey
// Create a compressed shared secret with a private key from only a public key
let sharedSecret = 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! P256K.Signing.PrivateKey()
let privateSign2 = try! P256K.Signing.PrivateKey()
let privateKey1 = try! P256K.KeyAgreement.PrivateKey(dataRepresentation: privateSign1.dataRepresentation)
let privateKey2 = try! P256K.KeyAgreement.PrivateKey(dataRepresentation: privateSign2.dataRepresentation)
let sharedSecret1 = privateKey1.sharedSecretFromKeyAgreement(with: privateKey2.publicKey)
let sharedSecret2 = privateKey2.sharedSecretFromKeyAgreement(with: privateKey1.publicKey)
let symmetricKey1 = SHA256.hash(data: sharedSecret1.bytes)
let symmetricKey2 = SHA256.hash(data: sharedSecret2.bytes)
let sharedSecretSign1 = try! P256K.Signing.PrivateKey(dataRepresentation: symmetricKey1.bytes)
let sharedSecretSign2 = try! P256K.Signing.PrivateKey(dataRepresentation: symmetricKey2.bytes)
// Spendable Silent Payment private key
let privateTweak1 = try! sharedSecretSign1.add(privateSign1.publicKey.xonly.bytes)
let publicTweak2 = try! sharedSecretSign2.publicKey.add(privateSign1.publicKey.xonly.bytes)
let schnorrPrivate = try! P256K.Schnorr.PrivateKey(dataRepresentation: sharedSecretSign2.dataRepresentation)
// Payable Silent Payment public key
let xonlyTweak2 = try! schnorrPrivate.xonly.add(privateSign1.publicKey.xonly.bytes)let privateKey = try! P256K.Recovery.PrivateKey()
let messageData = "We're all Satoshi.".data(using: .utf8)!
// Create a recoverable ECDSA signature
let recoverySignature = privateKey.signature(for: messageData)
// Recover an ECDSA public key from a signature
let publicKey = P256K.Recovery.PublicKey(messageData, signature: recoverySignature)
// Convert a recoverable signature into a normal signature
let signature = recoverySignature.normalizelet privateKey = try! P256K.Signing.PrivateKey()
let publicKey = try! P256K.Signing.PrivateKey().publicKey
// 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! P256K.Signing.PrivateKey(pemRepresentation: privateKeyString)// Initialize private keys for two signers
let firstPrivateKey = try! P256K.Schnorr.PrivateKey()
let secondPrivateKey = try! P256K.Schnorr.PrivateKey()
// Aggregate the public keys using MuSig
let aggregateKey = try! P256K.MuSig.aggregate([firstPrivateKey.publicKey, secondPrivateKey.publicKey])
// Message to be signed
let message = "Vires in Numeris.".data(using: .utf8)!
let messageHash = SHA256.hash(data: message)
// Generate nonces for each signer
let firstNonce = try! P256K.MuSig.Nonce.generate(
secretKey: firstPrivateKey,
publicKey: firstPrivateKey.publicKey,
msg32: Array(messageHash)
)
let secondNonce = try! P256K.MuSig.Nonce.generate(
secretKey: secondPrivateKey,
publicKey: secondPrivateKey.publicKey,
msg32: Array(messageHash)
)
// Aggregate nonces
let aggregateNonce = try! P256K.MuSig.Nonce(aggregating: [firstNonce.pubnonce, secondNonce.pubnonce])
// Create partial signatures
let firstPartialSignature = try! firstPrivateKey.partialSignature(
for: messageHash,
pubnonce: firstNonce.pubnonce,
secureNonce: firstNonce.secnonce,
publicNonceAggregate: aggregateNonce,
publicKeyAggregate: aggregateKey
)
let secondPartialSignature = try! secondPrivateKey.partialSignature(
for: messageHash,
pubnonce: secondNonce.pubnonce,
secureNonce: secondNonce.secnonce,
publicNonceAggregate: aggregateNonce,
publicKeyAggregate: aggregateKey
)
// Aggregate partial signatures into a full signature
let aggregateSignature = try! P256K.MuSig.aggregateSignatures([firstPartialSignature, secondPartialSignature])
// Verify the aggregate signature
let isValid = aggregateKey.isValidSignature(
firstPartialSignature,
publicKey: firstPrivateKey.publicKey,
nonce: firstNonce.pubnonce,
for: messageHash
)
print("Is valid MuSig signature: \(isValid)")For information on reporting security vulnerabilities, see SECURITY.md.
Contributions are welcome. Please read CONTRIBUTING.md for guidelines on how to get started. For AI-assisted development guidance, see AGENTS.md.
This project is released under the MIT License. See LICENSE for details.