Swift APIs for MuSig2 (#560)

* Initial Swift APIs for MuSig2

* Refactoring

* Added test for MuSig APIs

* Unit test passing

* Making secnonce non-Copyable

* Updating documentation

* Enable MuSig APIs in base library

* Bumping Swift version

* README updates

Exhaustive/Package/Dockerfile

@@ -1,5 +1,5 @@
 # Use an official Swift runtime image
-FROM swift:5.8.0
+FROM swift:6.0.1
 
 # Copies the root directory of the repository into the image's filesystem at `/LinuxTests`
 ADD . /LinuxTests

Exhaustive/Package/Package.swift

@@ -1,17 +1,17 @@
-// swift-tools-version: 5.6
+// swift-tools-version: 6.0
 
 import PackageDescription
 
 let package = Package(
     name: "Package",
     dependencies: [
-        .package(name: "secp256k1.swift", path: "../..")
+        .package(name: "swift-secp256k1", path: "../..")
     ],
     targets: [
         .testTarget(
             name: "secp256k1Tests",
             dependencies: [
-                .product(name: "secp256k1", package: "secp256k1.swift")
+                .product(name: "secp256k1", package: "swift-secp256k1")
             ]
         )
     ]

Package.swift

@@ -1,9 +1,9 @@
-// swift-tools-version:5.8
+// swift-tools-version: 6.0
 
 import PackageDescription
 
 let package = Package(
-    name: "secp256k1.swift",
+    name: "swift-secp256k1",
     products: [
         // WARNING: These APIs should not be considered stable and may change at any time.
         .library(name: "secp256k1", targets: ["secp256k1"]),
@@ -20,36 +20,16 @@ let package = Package(
         .target(name: "zkp", dependencies: ["zkp_bindings"]),
         .target(
             name: "secp256k1_bindings",
-            cSettings: [
-                // Basic config values that are universal and require no dependencies.
-                .define("ECMULT_GEN_PREC_BITS", to: "4"),
-                .define("ECMULT_WINDOW_SIZE", to: "15"),
-                // Enabling additional secp256k1 modules.
-                .define("ENABLE_MODULE_ECDH"),
-                .define("ENABLE_MODULE_ELLSWIFT"),
-                .define("ENABLE_MODULE_EXTRAKEYS"),
-                .define("ENABLE_MODULE_RECOVERY"),
-                .define("ENABLE_MODULE_SCHNORRSIG")
-            ]
+            cSettings: PackageDescription.CSetting.baseSettings
         ),
         .target(
             name: "zkp_bindings",
-            cSettings: [
-                // Basic config values that are universal and require no dependencies.
-                .define("ECMULT_GEN_PREC_BITS", to: "4"),
-                .define("ECMULT_WINDOW_SIZE", to: "15"),
-                // Enabling additional secp256k1-zkp modules.
+            cSettings: PackageDescription.CSetting.baseSettings + [
                 .define("ENABLE_MODULE_BPPP"),
-                .define("ENABLE_MODULE_ECDH"),
                 .define("ENABLE_MODULE_ECDSA_ADAPTOR"),
                 .define("ENABLE_MODULE_ECDSA_S2C"),
-                .define("ENABLE_MODULE_ELLSWIFT"),
-                .define("ENABLE_MODULE_EXTRAKEYS"),
                 .define("ENABLE_MODULE_GENERATOR"),
-                .define("ENABLE_MODULE_MUSIG"),
                 .define("ENABLE_MODULE_RANGEPROOF"),
-                .define("ENABLE_MODULE_RECOVERY"),
-                .define("ENABLE_MODULE_SCHNORRSIG"),
                 .define("ENABLE_MODULE_SCHNORRSIG_HALFAGG"),
                 .define("ENABLE_MODULE_SURJECTIONPROOF"),
                 .define("ENABLE_MODULE_WHITELIST"),
@@ -60,6 +40,21 @@ let package = Package(
         ),
         .testTarget(name: "zkpTests", dependencies: ["zkp"])
     ],
-    swiftLanguageVersions: [.v5],
+    swiftLanguageModes: [.v5],
     cLanguageStandard: .c89
 )
+
+extension PackageDescription.CSetting {
+    static let baseSettings: [Self] = [
+        // Basic config values that are universal and require no dependencies.
+        .define("ECMULT_GEN_PREC_BITS", to: "4"),
+        .define("ECMULT_WINDOW_SIZE", to: "15"),
+        // Enabling additional secp256k1 modules.
+        .define("ENABLE_MODULE_ECDH"),
+        .define("ENABLE_MODULE_ELLSWIFT"),
+        .define("ENABLE_MODULE_EXTRAKEYS"),
+        .define("ENABLE_MODULE_MUSIG"),
+        .define("ENABLE_MODULE_RECOVERY"),
+        .define("ENABLE_MODULE_SCHNORRSIG")
+    ]
+}

README.md

@@ -1,67 +1,77 @@
-[![Build Status](https://app.bitrise.io/app/18c18db60fc4fddf/status.svg?token=nczB4mTPCrlTfDQnXH_8Pw&branch=main)](https://app.bitrise.io/app/18c18db60fc4fddf) [![Build Status](https://app.bitrise.io/app/f1bbbdfeff08cd5c/status.svg?token=ONB3exCALsB-_ayi6KsXFQ&branch=main)](https://app.bitrise.io/app/f1bbbdfeff08cd5c) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FGigaBitcoin%2Fsecp256k1.swift%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/GigaBitcoin/secp256k1.swift) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2FGigaBitcoin%2Fsecp256k1.swift%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/GigaBitcoin/secp256k1.swift)
+[![Build Status](https://app.bitrise.io/app/18c18db60fc4fddf/status.svg?token=nczB4mTPCrlTfDQnXH_8Pw&branch=main)](https://app.bitrise.io/app/18c18db60fc4fddf) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2F21-DOT-DEV%2Fswift-secp256k1%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/21-DOT-DEV/swift-secp256k1) [![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2F21-DOT-DEV%2Fswift-secp256k1%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/21-DOT-DEV/swift-secp256k1)
 
-# 🔐 secp256k1.swift
-Swift package with elliptic curve public key cryptography, ECDSA, Schnorr Signatures for Bitcoin and C bindings from [libsecp256k1](https://github.com/bitcoin-core/secp256k1).
+# 🔐 swift-secp256k1
 
+Swift package for elliptic curve public key cryptography, ECDSA, and Schnorr Signatures for Bitcoin, with C bindings from [libsecp256k1](https://github.com/bitcoin-core/secp256k1).
 
-# Objectives
+## Objectives
 
-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](https://github.com/apple/swift-crypto)
- - Automatic updates for Swift and libsecp256k1
- - Availability for Linux and Apple platform ecosystems
+- Provide lightweight ECDSA & Schnorr Signatures functionality
+- Support simple and advanced usage, including BIP-327 and BIP-340
+- Expose C bindings for full control of the secp256k1 implementation
+- Offer a familiar API design inspired by [Swift Crypto](https://github.com/apple/swift-crypto)
+- Maintain automatic updates for Swift and libsecp256k1
+- Ensure availability for Linux and Apple platform ecosystems
 
+## Installation
 
-# Getting Started
+This package uses Swift Package Manager. To add it to your project:
 
-This repository primarily uses Swift package manager as its build tool, so we recommend using that as well. Xcode comes with [built-in support](https://developer.apple.com/documentation/xcode/adding-package-dependencies-to-your-app) 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:
+### Using Xcode
+
+1. Go to `File > Add Packages...`
+2. Enter the package URL: `https://github.com/21-DOT-DEV/swift-secp256k1`
+3. Select the desired version
+
+### Using Package.swift
+
+Add the following to your `Package.swift` file:
 
 ```swift
-.package(name: "secp256k1.swift", url: "https://github.com/GigaBitcoin/secp256k1.swift.git", exact: "0.15.0"),
+.package(name: "swift-secp256k1", url: "https://github.com/21-DOT-DEV/swift-secp256k1", exact: "0.18.0"),
 ```
 
-Include `secp256k1` as a dependency for your executable target:
+Then, include `secp256k1` as a dependency in your target:
 
 ```swift
 .target(name: "<target>", dependencies: [
-    .product(name: "secp256k1", package: "secp256k1.swift")
+    .product(name: "secp256k1", package: "swift-secp256k1")
 ]),
 ```
 
-Try in a [playground](spi-playgrounds://open?dependencies=GigaBitcoin/secp256k1.swift) using the [SPI Playgrounds app](https://swiftpackageindex.com/try-in-a-playground) or 🏟 [Arena](https://github.com/finestructure/arena)
+> [!WARNING]  
+> These APIs are not considered stable and may change with any update. Specify a version using `exact:` to avoid breaking changes.
 
-```swift
-arena GigaBitcoin/secp256k1.swift
-```
+### Try it out
 
+Use [SPI Playgrounds app](https://swiftpackageindex.com/try-in-a-playground):
 
-# Example Usage
+```swift
+arena 21-DOT-DEV/swift-secp256k1
+```
 
-## ECDSA
+## Usage Examples
 
+### ECDSA
 ```swift
 import secp256k1
 
-//  Private key
+// Private key
 let privateBytes = try! "14E4A74438858920D8A35FB2D88677580B6A2EE9BE4E711AE34EC6B396D87B5C".bytes
 let privateKey = try! secp256k1.Signing.PrivateKey(rawRepresentation: privateBytes)
 
-//  Public key
+// Public key
 print(String(bytes: privateKey.publicKey.rawRepresentation))
 
-// ECDSA
+// ECDSA signature
 let messageData = "We're all Satoshi.".data(using: .utf8)!
 let signature = try! privateKey.signature(for: messageData)
 
-//  DER signature
+// DER signature
 print(try! signature.derRepresentation.base64EncodedString())
 ```
 
-## Schnorr
-
+### Schnorr
 ```swift
 // Strict BIP340 mode is disabled by default for Schnorr signatures with variable length messages
 let privateKey = try! secp256k1.Schnorr.PrivateKey()
@@ -161,7 +171,63 @@ oUQDQgAEt2uDn+2GqqYs/fmkBr5+rCQ3oiFSIJMAcjHIrTDS6HEELgguOatmFBOp
 let privateKey = try! secp256k1.Signing.PrivateKey(pemRepresentation: privateKeyString)
 ```
 
+## MuSig2
 
-# Danger
-These APIs should not be considered stable and may change at any time.
-
+```swift
+// Initialize private keys for two signers
+let firstPrivateKey = try secp256k1.Schnorr.PrivateKey()
+let secondPrivateKey = try secp256k1.Schnorr.PrivateKey()
+
+// Aggregate the public keys using MuSig
+let aggregateKey = try secp256k1.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 secp256k1.MuSig.Nonce.generate(
+    secretKey: firstPrivateKey,
+    publicKey: firstPrivateKey.publicKey,
+    msg32: Array(messageHash)
+)
+
+let secondNonce = try secp256k1.MuSig.Nonce.generate(
+    secretKey: secondPrivateKey,
+    publicKey: secondPrivateKey.publicKey,
+    msg32: Array(messageHash)
+)
+
+// Aggregate nonces
+let aggregateNonce = try secp256k1.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 secp256k1.MuSig.aggregateSignatures([firstPartialSignature, secondPartialSignature])
+
+// Verify the aggregate signature
+let isValid = aggregateKey.isValidSignature(
+    aggregateSignature,
+    publicKey: firstPublicKey,
+    nonce: firstNonce.pubnonce,
+    for: messageHash
+)
+
+print("Is valid MuSig signature: \(isValid)")
+```

Sources/secp256k1/MuSig.swift

@@ -0,0 +1 @@
+../zkp/MuSig.swift

Sources/secp256k1/Nonces.swift

@@ -0,0 +1 @@
+../zkp/Nonces.swift

Sources/secp256k1_bindings/include/secp256k1_musig.h

@@ -0,0 +1 @@
+../../../Submodules/secp256k1/include/secp256k1_musig.h

Sources/secp256k1_bindings/src/modules/musig/keyagg.h

@@ -0,0 +1 @@
+../../../../../Submodules/secp256k1/src/modules/musig/keyagg.h

Sources/secp256k1_bindings/src/modules/musig/keyagg_impl.h

@@ -0,0 +1 @@
+../../../../../Submodules/secp256k1/src/modules/musig/keyagg_impl.h

Sources/secp256k1_bindings/src/modules/musig/main_impl.h

@@ -0,0 +1 @@
+../../../../../Submodules/secp256k1/src/modules/musig/main_impl.h

Sources/secp256k1_bindings/src/modules/musig/session.h

@@ -0,0 +1 @@
+../../../../../Submodules/secp256k1/src/modules/musig/session.h

Sources/secp256k1_bindings/src/modules/musig/session_impl.h

@@ -0,0 +1 @@
+../../../../../Submodules/secp256k1/src/modules/musig/session_impl.h

Sources/zkp/Asymmetric.swift

@@ -249,7 +249,7 @@ public extension secp256k1 {
             /// - Parameter data: A data representation of the x-only public key.
             /// - Parameter keyParity: The key parity as an `Int32`.
             public init<D: ContiguousBytes>(dataRepresentation data: D, keyParity: Int32) {
-                self.baseKey = XonlyKeyImplementation(dataRepresentation: data, keyParity: keyParity)
+                self.baseKey = XonlyKeyImplementation(dataRepresentation: data.bytes, keyParity: keyParity)
             }
         }
     }

Sources/zkp/Combine.swift

@@ -23,38 +23,12 @@ public extension secp256k1.Signing.PublicKey {
         var combinedKey = secp256k1_pubkey()
         var combinedBytes = [UInt8](repeating: 0, count: pubKeyLen)
 
-        guard withUnsafePointersToPubKeys(allPubKeys.map { $0.rawRepresentation }, { ptrsToCombine in
-            secp256k1_ec_pubkey_combine(context, &combinedKey, ptrsToCombine, ptrsToCombine.count).boolValue
+        guard PointerArrayUtility.withUnsafePointerArray(allPubKeys.map { $0.rawRepresentation }, { pointers in
+            secp256k1_ec_pubkey_combine(context, &combinedKey, pointers, pointers.count).boolValue
         }), secp256k1_ec_pubkey_serialize(context, &combinedBytes, &pubKeyLen, &combinedKey, format.rawValue).boolValue else {
             throw secp256k1Error.underlyingCryptoError
         }
 
         return try Self(dataRepresentation: combinedBytes, format: format)
     }
 }
-
-extension secp256k1.Signing.PublicKey {
-    /// Executes a closure with an array of `UnsafePointer<secp256k1_pubkey>?` for pointer operations on an array of `secp256k1_pubkey`.
-    /// - Parameters:
-    ///   - pubKeys: An array of `secp256k1_pubkey` to be converted to `UnsafePointer<secp256k1_pubkey>?`.
-    ///   - body: A closure that takes an array of `UnsafePointer<secp256k1_pubkey>?` and returns a result of type `Result`.
-    /// - Returns: The result of the closure of type `Result`.
-    func withUnsafePointersToPubKeys<Result>(
-        _ pubKeys: [secp256k1_pubkey],
-        _ body: ([UnsafePointer<secp256k1_pubkey>?]) -> Result
-    ) -> Result {
-        let pointers = pubKeys.map { pubKey -> UnsafePointer<secp256k1_pubkey>? in
-            let mutablePubKey = UnsafeMutablePointer<secp256k1_pubkey>.allocate(capacity: 1)
-            mutablePubKey.initialize(to: pubKey)
-            return UnsafePointer(mutablePubKey)
-        }
-
-        defer {
-            for ptr in pointers {
-                ptr?.deallocate()
-            }
-        }
-
-        return body(pointers)
-    }
-}