[WIP] Omemo signauture

Component_Tests/Classes/Crypto/Omemo/Test_KeyHelper.cs

@@ -63,5 +63,37 @@ public void Test_SignPreKey()
                 Assert.AreEqual(sigBase64, sigRefBase64);
             }
         }
+
+        [TestCategory("Crypto")]
+        [TestMethod]
+        public void Test_Signing()
+        {
+            ECPrivKeyModel identityPriv = new ECPrivKeyModel(SharedUtils.HexStringToByteArray("1498b5467a63dffa2dc9d9e069caf075d16fc33fdd4c3b01bfadae6433767d93"));
+            ECPubKeyModel identityPub = new ECPubKeyModel(SharedUtils.HexStringToByteArray("05b7a3c12dc0c8c748ab07525b701122b88bd78f600c76342d27f25e5f92444cde"));
+
+            ECPrivKeyModel prePriv = new ECPrivKeyModel(SharedUtils.HexStringToByteArray("181c0ed79c361f2d773f3aa8d5934569395a1c1b4a8514d140a7dcde92688579"));
+            ECPubKeyModel prePub = new ECPubKeyModel(SharedUtils.HexStringToByteArray("05b30aad2471f7186bdb34951747cf81a67245144260e20ffe5bf7748202d6572c"));
+            PreKeyModel preKey = new PreKeyModel(prePriv, prePub, 2);
+
+            byte[] sig = KeyHelper.SignPreKey(preKey, identityPriv);
+            string sig16 = SharedUtils.ToHexString(sig);
+            Assert.IsTrue(KeyHelper.VerifySignature(identityPub, prePub, sig));
+        }
+
+        [TestCategory("Crypto")]
+        [TestMethod]
+        public void Test_VerifySignature()
+        {
+            ECPubKeyModel identityPub = new ECPubKeyModel(SharedUtils.HexStringToByteArray("05b7a3c12dc0c8c748ab07525b701122b88bd78f600c76342d27f25e5f92444cde"));
+            ECPubKeyModel prePub = new ECPubKeyModel(SharedUtils.HexStringToByteArray("05b30aad2471f7186bdb34951747cf81a67245144260e20ffe5bf7748202d6572c"));
+            byte[][] sigs = {
+                SharedUtils.HexStringToByteArray("db0495131504b9acf87696613070088abff5310ad984f3b7623088af6310e2435381f2f726cfcc3edc754549d47e251d873d5b6777dd62a334b5d3fa8afb9f0a")
+            };
+
+            foreach (byte[] sig in sigs)
+            {
+                Assert.IsTrue(KeyHelper.VerifySignature(identityPub, prePub, sig));
+            }
+        }
     }
 }

Component_Tests/Classes/Crypto/Omemo/Test_Xeddsa25519.cs

@@ -0,0 +1,22 @@
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Omemo.Classes.Keys;
+using Omemo.Classes.Xeddsa;
+using Shared.Classes;
+
+namespace Component_Tests.Classes.Crypto.Omemo
+{
+    [TestClass]
+    public class Test_Xeddsa25519
+    {
+        [TestCategory("Crypto")]
+        [TestMethod]
+        public void Test_Signing()
+        {
+            ECPrivKeyModel priv = new ECPrivKeyModel(SharedUtils.HexStringToByteArray("1498b5467a63dffa2dc9d9e069caf075d16fc33fdd4c3b01bfadae6433767d93"));
+            ECPubKeyModel pub = new ECPubKeyModel(SharedUtils.HexStringToByteArray("b7a3c12dc0c8c748ab07525b701122b88bd78f600c76342d27f25e5f92444cde"));
+            IdentityKeyPairModel identityKeyPair = new IdentityKeyPairModel(priv, pub);
+            // Xeddsa25519.Sign(identityKeyPair.privKey, pub new );
+            Xeddsa25519.ToTwistedEdwardsKeyPair(priv);
+        }
+    }
+}

Component_Tests/Component_Tests.csproj

@@ -131,6 +131,7 @@
     <Compile Include="Classes\Crypto\Omemo\InMemmoryOmemoStorage.cs" />
     <Compile Include="Classes\Crypto\Omemo\Test_KeyHelper.cs" />
     <Compile Include="Classes\Crypto\Omemo\Test_Omemo.cs" />
+    <Compile Include="Classes\Crypto\Omemo\Test_Xeddsa25519.cs" />
     <Compile Include="Classes\Crypto\Test_CryptoUtils.cs" />
     <Compile Include="Classes\Misc\Test_DateTimeParserHelper.cs" />
     <Compile Include="Classes\Misc\Test_ConsistentColorGenerator.cs" />

Omemo/Classes/Keys/AbstractECKeyPairModel.cs → Omemo/Classes/Keys/ECKeyPairModel.cs

@@ -6,7 +6,7 @@
 
 namespace Omemo.Classes.Keys
 {
-    public abstract class AbstractECKeyPairModel: AbstractDataTemplate
+    public class ECKeyPairModel: AbstractDataTemplate
     {
         //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
         #region --Attributes--
@@ -38,9 +38,9 @@ public ECPubKeyModel pubKey
         #endregion
         //--------------------------------------------------------Constructor:----------------------------------------------------------------\\
         #region --Constructors--
-        public AbstractECKeyPairModel() { }
+        public ECKeyPairModel() { }
 
-        public AbstractECKeyPairModel(ECPrivKeyModel privKey, ECPubKeyModel pubKey)
+        public ECKeyPairModel(ECPrivKeyModel privKey, ECPubKeyModel pubKey)
         {
             this.privKey = privKey;
             this.pubKey = pubKey;
@@ -86,7 +86,7 @@ private void SetPubKeyProperty(ECPubKeyModel value)
         #region --Misc Methods (Public)--
         public override bool Equals(object obj)
         {
-            return obj is AbstractECKeyPairModel pair && ((pair.privKey is null && privKey is null) || pair.privKey.Equals(privKey)) && ((pair.pubKey is null && pubKey is null) || pair.pubKey.Equals(pubKey));
+            return obj is ECKeyPairModel pair && ((pair.privKey is null && privKey is null) || pair.privKey.Equals(privKey)) && ((pair.pubKey is null && pubKey is null) || pair.pubKey.Equals(pubKey));
         }
 
         public override int GetHashCode()

Omemo/Classes/Keys/ECPrivKeyModel.cs

@@ -16,14 +16,14 @@ public class ECPrivKeyModel: ECKeyModel
         /// </summary>
         public ECPrivKeyModel() { }
 
-        public ECPrivKeyModel(byte[] pubKey) : base(pubKey)
+        public ECPrivKeyModel(byte[] privKey) : base(privKey)
         {
-            if (pubKey.Length == KeyHelper.PUB_KEY_SIZE)
+            if (privKey.Length == KeyHelper.PUB_KEY_SIZE)
             {
                 return;
             }
 
-            throw new OmemoKeyException($"Invalid key length {pubKey.Length} - expected {KeyHelper.PRIV_KEY_SIZE}.");
+            throw new OmemoKeyException($"Invalid key length {privKey.Length} - expected {KeyHelper.PRIV_KEY_SIZE}.");
         }
 
         #endregion

Omemo/Classes/Keys/EphemeralKeyPairModel.cs

@@ -3,7 +3,7 @@
     /// <summary>
     /// Represents a Ed25519 key pair.
     /// </summary>
-    public class EphemeralKeyPairModel: AbstractECKeyPairModel
+    public class EphemeralKeyPairModel: ECKeyPairModel
     {
         //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
         #region --Attributes--

Omemo/Classes/Keys/GenericECKeyPairModel.cs

@@ -3,7 +3,7 @@
     /// <summary>
     /// Represents a generic EC key pair holding a <see cref="ECPubKeyModel"/> and <see cref="ECPrivKeyModel"/>.
     /// </summary>
-    public class GenericECKeyPairModel: AbstractECKeyPairModel
+    public class GenericECKeyPairModel: ECKeyPairModel
     {
         //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
         #region --Attributes--

Omemo/Classes/Keys/IdentityKeyPairModel.cs

@@ -3,7 +3,7 @@
     /// <summary>
     /// Represents a Ed25519 key pair.
     /// </summary>
-    public class IdentityKeyPairModel: AbstractECKeyPairModel
+    public class IdentityKeyPairModel: ECKeyPairModel
     {
         //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
         #region --Attributes--

Omemo/Classes/Keys/PreKeyModel.cs

@@ -3,7 +3,7 @@
 
 namespace Omemo.Classes.Keys
 {
-    public class PreKeyModel: AbstractECKeyPairModel
+    public class PreKeyModel: ECKeyPairModel
     {
         //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
         #region --Attributes--

Omemo/Classes/Xeddsa/ECPoint.cs

@@ -0,0 +1,69 @@
+using Org.BouncyCastle.Math;
+
+namespace Omemo.Classes.Xeddsa
+{
+    public class ECPoint
+    {
+        //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
+        #region --Attributes--
+        public BigInteger y;
+        public bool s;
+
+        #endregion
+        //--------------------------------------------------------Constructor:----------------------------------------------------------------\\
+        #region --Constructors--
+        public ECPoint(byte[] point)
+        {
+            // Decoding described in: https://datatracker.ietf.org/doc/html/rfc8032#section-5.1.3
+            BigInteger tmp = new BigInteger(point);
+            s = ((point[31] & 0x80) >> 7) == 1;
+            y = tmp.ClearBit(255);
+        }
+
+        public ECPoint(BigInteger y, bool s)
+        {
+            this.y = y;
+            this.s = s;
+        }
+
+        #endregion
+        //--------------------------------------------------------Set-, Get- Methods:---------------------------------------------------------\\
+        #region --Set-, Get- Methods--
+
+
+        #endregion
+        //--------------------------------------------------------Misc Methods:---------------------------------------------------------------\\
+        #region --Misc Methods (Public)--
+        public byte[] Encode()
+        {
+            // Encoding described in: https://datatracker.ietf.org/doc/html/rfc8032#section-5.1.2
+            BigInteger point = new BigInteger(y.ToByteArray());
+            if (s)
+            {
+                point.SetBit(255);
+            }
+            else
+            {
+                point.ClearBit(255);
+            }
+            return point.ToByteArray();
+        }
+
+        #endregion
+
+        #region --Misc Methods (Private)--
+
+
+        #endregion
+
+        #region --Misc Methods (Protected)--
+
+
+        #endregion
+        //--------------------------------------------------------Events:---------------------------------------------------------------------\\
+        #region --Events--
+
+
+        #endregion
+    }
+}

Omemo/Classes/Xeddsa/Xeddsa25519.cs

@@ -0,0 +1,114 @@
+using System.Diagnostics;
+using NSec.Cryptography;
+using Omemo.Classes.Keys;
+using Org.BouncyCastle.Math;
+
+namespace Omemo.Classes.Xeddsa
+{
+    /// <summary>
+    /// Notes:
+    /// Curve25519 -> Montgomery
+    /// edwards25519 (Ed25519) -> Twisted Edwards
+    /// Ed25519 is a public-key signature system with several attractive features (https://ed25519.cr.yp.to/)
+    /// Ed25519 as defined in:
+    /// https://tools.ietf.org/html/rfc7748
+    /// https://tools.ietf.org/html/rfc8032
+    /// </summary>
+    public class Xeddsa25519
+    {
+        //--------------------------------------------------------Attributes:-----------------------------------------------------------------\\
+        #region --Attributes--
+        private static readonly BigInteger p = BigInteger.Two.Pow(255).Subtract(BigInteger.ValueOf(19));
+
+        private static readonly byte[] MINUS_ONE = new byte[] {0xec, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58,
+                                    0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14,
+                                    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10};
+
+        #endregion
+        //--------------------------------------------------------Constructor:----------------------------------------------------------------\\
+        #region --Constructors--
+
+
+        #endregion
+        //--------------------------------------------------------Set-, Get- Methods:---------------------------------------------------------\\
+        #region --Set-, Get- Methods--
+
+
+        #endregion
+        //--------------------------------------------------------Misc Methods:---------------------------------------------------------------\\
+        #region --Misc Methods (Public)--
+        /// <summary>
+        /// Signes the given <paramref name="msg"/> and returns the result.
+        /// </summary>
+        /// <param name="privKey">The Curve25519 (Montgomery) private key used for signing.</param>
+        /// <param name="msg">The message that should be signed.</param>
+        /// <param name="random">64 bytes secure random data used for signing.</param>
+        /// <returns>The generated signature for the given <paramref name="msg"/>.</returns>
+        public static byte[] Sign(ECPrivKeyModel privKey, byte[] msg, byte[] random)
+        {
+            Debug.Assert(random.Length == 64);
+            Debug.Assert(msg.Length > 0);
+
+            ECKeyPairModel edKeyPair = ToTwistedEdwardsKeyPair(privKey);
+
+            Key key = Key.Import(SignatureAlgorithm.Ed25519, edKeyPair.privKey.key, KeyBlobFormat.RawPrivateKey);
+            return SignatureAlgorithm.Ed25519.Sign(key, msg);
+        }
+
+        #endregion
+
+        #region --Misc Methods (Private)--
+        public static ECKeyPairModel ToTwistedEdwardsKeyPair(ECPrivKeyModel privKey)
+        {
+            byte[] A = new byte[Org.BouncyCastle.Math.EC.Rfc7748.X25519.PointSize];
+            byte[] A2 = new byte[Org.BouncyCastle.Math.EC.Rfc7748.X25519.PointSize];
+            Org.BouncyCastle.Math.EC.Rfc7748.X25519.ScalarMultBase(privKey.key, 0, A2, 0);
+            byte[] u = Shared.Classes.SharedUtils.HexStringToByteArray("5866666666666666666666666666666666666666666666666666666666666666");
+            Org.BouncyCastle.Math.EC.Rfc7748.X25519.ScalarMult(privKey.key, 0, u, 0, A, 0);
+
+            byte s = (byte)((A[31] & 0x80) >> 7);
+            byte[] a = new byte[Org.BouncyCastle.Math.EC.Rfc7748.X25519.PointSize];
+            privKey.key.CopyTo(a, 0);
+            byte[] aNeg = new byte[Org.BouncyCastle.Math.EC.Rfc7748.X25519.PointSize];
+
+            Org.BouncyCastle.Math.EC.Rfc7748.X25519.ScalarMult(MINUS_ONE, 0, a, 0, aNeg, 0);
+            sc_cmov(a, aNeg, s);
+            A[31] &= 0x7F;
+
+            return new ECKeyPairModel(new ECPrivKeyModel(a), new ECPubKeyModel(A));
+        }
+
+        private static void sc_cmov(byte[] f, byte[] g, byte b)
+        {
+            byte[] x = new byte[32];
+            for (int count = 0; count < 32; count++)
+            {
+                x[count] = (byte)(f[count] ^ g[count]);
+            }
+            b = (byte)-b;
+            for (int count = 0; count < 32; count++)
+            {
+                x[count] &= b;
+            }
+
+            for (int count = 0; count < 32; count++)
+            {
+                f[count] = (byte)(f[count] ^ x[count]);
+            }
+        }
+
+
+        #endregion
+
+        #region --Misc Methods (Protected)--
+
+
+        #endregion
+        //--------------------------------------------------------Events:---------------------------------------------------------------------\\
+        #region --Events--
+
+
+        #endregion
+    }
+}

Omemo/Omemo.csproj

@@ -130,7 +130,7 @@
     <Compile Include="Classes\KeyHelper.cs" />
     <Compile Include="Classes\Keys\Bundle.cs" />
     <Compile Include="Classes\Keys\ECKeyModel.cs" />
-    <Compile Include="Classes\Keys\AbstractECKeyPairModel.cs" />
+    <Compile Include="Classes\Keys\ECKeyPairModel.cs" />
     <Compile Include="Classes\Keys\ECPrivKeyModel.cs" />
     <Compile Include="Classes\Keys\ECPubKeyModel.cs" />
     <Compile Include="Classes\Keys\EphemeralKeyPairModel.cs" />
@@ -150,6 +150,8 @@
     <Compile Include="Classes\SkippedMessageKeyModel.cs" />
     <Compile Include="Classes\SkippedMessageKeyGroupModel.cs" />
     <Compile Include="Classes\SkippedMessageKeyGroupsModel.cs" />
+    <Compile Include="Classes\Xeddsa\ECPoint.cs" />
+    <Compile Include="Classes\Xeddsa\Xeddsa25519.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <EmbeddedResource Include="Properties\Omemo.rd.xml" />
   </ItemGroup>
@@ -182,6 +184,7 @@
       <Name>Visual C++ 2015-2019 UWP Desktop Runtime for native apps</Name>
     </SDKReference>
   </ItemGroup>
+  <ItemGroup />
   <PropertyGroup Condition=" '$(VisualStudioVersion)' == '' or '$(VisualStudioVersion)' &lt; '14.0' ">
     <VisualStudioVersion>14.0</VisualStudioVersion>
   </PropertyGroup>