From 5d39db9caba42ca0dea978f870e323f23ed8b1a3 Mon Sep 17 00:00:00 2001
From: Matthew Mitchell <mattlmitchell@proton.me>
Date: Fri, 30 Aug 2024 21:38:39 +0100
Subject: [PATCH] Add ECCompressedPublicKey class

---
 coinlib/lib/src/coinlib_base.dart             |  1 +
 .../src/crypto/ec_compressed_public_key.dart  | 31 +++++++++
 .../crypto/ec_compressed_public_key_test.dart | 65 +++++++++++++++++++
 coinlib/test/crypto/ec_public_key_test.dart   | 14 ++--
 coinlib/test/vectors/keys.dart                |  1 +
 5 files changed, 104 insertions(+), 8 deletions(-)
 create mode 100644 coinlib/lib/src/crypto/ec_compressed_public_key.dart
 create mode 100644 coinlib/test/crypto/ec_compressed_public_key_test.dart

diff --git a/coinlib/lib/src/coinlib_base.dart b/coinlib/lib/src/coinlib_base.dart
index 5361a44..bc5c12e 100644
--- a/coinlib/lib/src/coinlib_base.dart
+++ b/coinlib/lib/src/coinlib_base.dart
@@ -4,6 +4,7 @@ export 'package:coinlib/src/common/bytes.dart';
 export 'package:coinlib/src/common/hex.dart';
 export 'package:coinlib/src/common/serial.dart';
 
+export 'package:coinlib/src/crypto/ec_compressed_public_key.dart';
 export 'package:coinlib/src/crypto/ec_private_key.dart';
 export 'package:coinlib/src/crypto/ec_public_key.dart';
 export 'package:coinlib/src/crypto/ecdsa_signature.dart';
diff --git a/coinlib/lib/src/crypto/ec_compressed_public_key.dart b/coinlib/lib/src/crypto/ec_compressed_public_key.dart
new file mode 100644
index 0000000..224bede
--- /dev/null
+++ b/coinlib/lib/src/crypto/ec_compressed_public_key.dart
@@ -0,0 +1,31 @@
+import 'dart:typed_data';
+
+import 'package:coinlib/src/common/hex.dart';
+import 'ec_public_key.dart';
+
+/// Represents an [ECPublicKey] that must be in a compressed format, or else a
+/// [InvalidPublicKey] will be thrown.
+class ECCompressedPublicKey extends ECPublicKey {
+
+  ECCompressedPublicKey(super.data) {
+    if (data.length != 33) throw InvalidPublicKey();
+  }
+  ECCompressedPublicKey.fromHex(String hex) : this(hexToBytes(hex));
+  ECCompressedPublicKey.fromXOnly(super.xcoord) : super.fromXOnly();
+  ECCompressedPublicKey.fromXOnlyHex(super.hex) : super.fromXOnlyHex();
+  ECCompressedPublicKey.fromPubkey(ECPublicKey key) : this(
+    key.compressed
+    ? key.data
+    : Uint8List.fromList([key.yIsEven ? 2 : 3, ...key.x]),
+  );
+
+  @override
+  ECCompressedPublicKey? tweak(Uint8List scalar) {
+    final tweaked = super.tweak(scalar);
+    return tweaked == null ? null : ECCompressedPublicKey.fromPubkey(tweaked);
+  }
+
+  @override
+  ECCompressedPublicKey get xonly => ECCompressedPublicKey.fromXOnly(x);
+
+}
diff --git a/coinlib/test/crypto/ec_compressed_public_key_test.dart b/coinlib/test/crypto/ec_compressed_public_key_test.dart
new file mode 100644
index 0000000..353a714
--- /dev/null
+++ b/coinlib/test/crypto/ec_compressed_public_key_test.dart
@@ -0,0 +1,65 @@
+import 'package:coinlib/coinlib.dart';
+import 'package:test/test.dart';
+import '../vectors/keys.dart';
+
+void main() {
+
+  group("ECCompressedPublicKey", () {
+
+    setUpAll(loadCoinlib);
+
+    test("requires 33 bytes", () {
+
+      for (final failing in [
+        // Too small
+        pubkeyVec.substring(0, 32*2),
+        // Too large
+        longPubkeyVec,
+        "${pubkeyVec}ff",
+      ]) {
+        expect(
+          () => ECCompressedPublicKey.fromHex(failing),
+          throwsA(isA<InvalidPublicKey>()),
+        );
+      }
+
+    });
+
+    test("accepts compressed types", () {
+      for (final vec in validPubKeys) {
+        if (!vec.compressed) continue;
+        final pk = ECCompressedPublicKey.fromHex(vec.hex);
+        expect(pk.hex, vec.hex);
+        expect(pk.compressed, true);
+        expect(pk.yIsEven, vec.evenY);
+      }
+    });
+
+    test(".fromXOnly", () => expect(
+        ECCompressedPublicKey.fromXOnlyHex(xOnlyPubkeyVec).hex,
+        "02$xOnlyPubkeyVec",
+    ),);
+
+    test(".fromPubkey", () {
+
+      void expectCompressedKey(String pubkey, String compressed) => expect(
+        ECCompressedPublicKey.fromPubkey(ECPublicKey.fromHex(pubkey)).hex,
+        compressed,
+      );
+
+      expectCompressedKey(longPubkeyVec, pubkeyVec);
+      expectCompressedKey(pubkeyVec, pubkeyVec);
+      expectCompressedKey(
+        "06ef164284e2c3abc32b310eb62904af0d49196c51087bdf4038998f8818787c882433ae83422904f48ad36dcf351ac9a37e6b00e57cf40b469b650ec850640efe",
+        "02ef164284e2c3abc32b310eb62904af0d49196c51087bdf4038998f8818787c88",
+      );
+      expectCompressedKey(
+        "07576168b540f6f80e4d2a325f8cbd420ceb170ff42cd07e96bffc5e6a4a4ea04b1208f618306fd629cd2972cea45aa81ae7b24a64bf2e86704d7a63d82fd97a8f",
+        "03576168b540f6f80e4d2a325f8cbd420ceb170ff42cd07e96bffc5e6a4a4ea04b",
+      );
+
+    });
+
+  });
+
+}
diff --git a/coinlib/test/crypto/ec_public_key_test.dart b/coinlib/test/crypto/ec_public_key_test.dart
index e4c4b27..4955124 100644
--- a/coinlib/test/crypto/ec_public_key_test.dart
+++ b/coinlib/test/crypto/ec_public_key_test.dart
@@ -14,11 +14,11 @@ void main() {
 
       for (final failing in [
         // Too small
-        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
-        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f",
+        pubkeyVec.substring(0, 32*2),
+        longPubkeyVec.substring(0, 32*2),
         // Too large
-        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f2021",
-        "000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f2021",
+        "${pubkeyVec}ff",
+        "${longPubkeyVec}ff",
       ]) {
         expect(
           () => ECPublicKey.fromHex(failing),
@@ -46,10 +46,8 @@ void main() {
     test(".fromXOnly", () {
 
       expect(
-        ECPublicKey.fromXOnlyHex(
-          "d69c3509bb99e412e68b0fe8544e72837dfa30746d8be2aa65975f29d22dc7b9",
-        ).hex,
-        "02d69c3509bb99e412e68b0fe8544e72837dfa30746d8be2aa65975f29d22dc7b9",
+        ECCompressedPublicKey.fromXOnlyHex(xOnlyPubkeyVec).hex,
+        "02$xOnlyPubkeyVec",
       );
 
       for (final invalid in [
diff --git a/coinlib/test/vectors/keys.dart b/coinlib/test/vectors/keys.dart
index f065900..be39abc 100644
--- a/coinlib/test/vectors/keys.dart
+++ b/coinlib/test/vectors/keys.dart
@@ -20,6 +20,7 @@ class KeyTestVector {
 final pubkeyVec = "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798";
 final longPubkeyVec = "0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8";
 final pubkeyhashVec = "751e76e8199196d454941c45d1b3a323f1433bd6";
+final xOnlyPubkeyVec = "d69c3509bb99e412e68b0fe8544e72837dfa30746d8be2aa65975f29d22dc7b9";
 
 final keyPairVectors = [
   KeyTestVector(