From 7c3536b995438bcb0c46596afd1c159e0d17d737 Mon Sep 17 00:00:00 2001
From: Simon McLoughlin <simon.d.mcl@gmail.com>
Date: Thu, 1 Jun 2023 14:14:04 +0100
Subject: [PATCH] add secp256k1 uncompress function + tests

---
 Sources/KukaiCryptoSwift/KeyPair.swift        | 21 +++++++++++++++++-
 .../KukaiCryptoSwiftTests/KeyPairTests.swift  | 22 +++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Sources/KukaiCryptoSwift/KeyPair.swift b/Sources/KukaiCryptoSwift/KeyPair.swift
index cbb0873..1488373 100644
--- a/Sources/KukaiCryptoSwift/KeyPair.swift
+++ b/Sources/KukaiCryptoSwift/KeyPair.swift
@@ -135,7 +135,7 @@ public struct KeyPair {
 	
 	
 	
-	// MARK: - Private Helpers
+	// MARK: - Helpers
 	
 	/// Helper method to take a secp256k1 private key (for a regualr keypair) and use it to create a public key for the same curve
 	public static func secp256k1PublicKey(fromPrivateKeyBytes pkBytes: [UInt8]) -> PublicKey? {
@@ -156,4 +156,23 @@ public struct KeyPair {
 		
 		return PublicKey(publicKeyBytes, signingCurve: .secp256k1)
 	}
+	
+	/// Helper method to uncompress a secp256k1 public key
+	public static func secp256k1PublicKey_uncompressed(fromBytes: [UInt8]) -> [UInt8] {
+		var publicKey = secp256k1_pubkey()
+		var outputLength = 65
+		var outputBytes = [UInt8](repeating: 0, count: outputLength)
+		
+		guard let context = secp256k1_context_create(UInt32(SECP256K1_CONTEXT_SIGN)),
+			  secp256k1_ec_pubkey_parse(context, &publicKey, fromBytes, fromBytes.count) != 0,
+			  secp256k1_ec_pubkey_serialize(context, &outputBytes, &outputLength, &publicKey, UInt32(SECP256K1_EC_UNCOMPRESSED)) != 0 else {
+			return []
+		}
+		
+		defer {
+			secp256k1_context_destroy(context)
+		}
+		
+		return outputBytes
+	}
 }
diff --git a/Tests/KukaiCryptoSwiftTests/KeyPairTests.swift b/Tests/KukaiCryptoSwiftTests/KeyPairTests.swift
index 936d3dd..4b31b39 100644
--- a/Tests/KukaiCryptoSwiftTests/KeyPairTests.swift
+++ b/Tests/KukaiCryptoSwiftTests/KeyPairTests.swift
@@ -102,4 +102,26 @@ final class KeyPairTests: XCTestCase {
 		XCTAssert(EllipticalCurve.fromAddress("tZ1abc123") == .ed25519)
 		XCTAssert(EllipticalCurve.fromAddress("tZ2abc123") == .secp256k1)
 	}
+	
+	func testUncompress() throws {
+		let mnemonic = try Mnemonic(seedPhrase: "gym exact clown can answer hope sample mirror knife twenty powder super imitate lion churn almost shed chalk dust civil gadget pyramid helmet trade")
+		let keyPair1 = KeyPair.regular(fromMnemonic: mnemonic, passphrase: "", andSigningCurve: .secp256k1)
+		
+		let uncompressed = KeyPair.secp256k1PublicKey_uncompressed(fromBytes: keyPair1?.publicKey.bytes ?? [])
+		let data = Data(bytes: uncompressed, count: uncompressed.count)
+		let dataString = data.hexString
+		
+		XCTAssert(dataString.count == 130, dataString.count.description)
+		XCTAssert(dataString == "047b6d7bf2cbb376149211eacab517359cb035b0f0c36f57f7fe923a2453c7a8f1a594260c94501bc7ad63324b42638f768840948d1f1cadf9cb6d1ce456b7c8dc", dataString)
+		
+		
+		let keyPair2 = KeyPair.regular(fromMnemonic: mnemonic, passphrase: "", andSigningCurve: .ed25519)
+		
+		let uncompressed2 = KeyPair.secp256k1PublicKey_uncompressed(fromBytes: keyPair2?.publicKey.bytes ?? [])
+		let data2 = Data(bytes: uncompressed2, count: uncompressed2.count)
+		let dataString2 = data2.hexString
+		
+		XCTAssert(dataString2.count == 0, dataString2.count.description)
+		XCTAssert(dataString2 == "", dataString2)
+	}
 }