From c735f9431cd2399465f5328aafc51f5c5ed44676 Mon Sep 17 00:00:00 2001
From: Stefan Rinkes <stefan.rinkes@gmail.com>
Date: Mon, 26 Nov 2018 20:15:25 +0100
Subject: [PATCH] Add Support for ECDSA Host- and Private-Keys

Also known as:
- ecdsa-sha2-nistp256
- ecdsa-sha2-nistp384
- ecdsa-sha2-nistp521

Basically it translate between SSH-Data and Microsoft Crypto API.
---
 .../Renci.SshNet.NET35.csproj                 |  10 +-
 .../Renci.SshNet.Tests.NET35.csproj           |  20 +
 .../Classes/PrivateKeyFileTest.cs             |  66 ++++
 .../Data/Key.ECDSA.Encrypted.txt              |   8 +
 src/Renci.SshNet.Tests/Data/Key.ECDSA.txt     |   5 +
 .../Data/Key.ECDSA384.Encrypted.txt           |   9 +
 src/Renci.SshNet.Tests/Data/Key.ECDSA384.txt  |   6 +
 .../Data/Key.ECDSA521.Encrypted.txt           |  10 +
 src/Renci.SshNet.Tests/Data/Key.ECDSA521.txt  |   7 +
 .../Renci.SshNet.Tests.csproj                 |   8 +
 src/Renci.SshNet/Common/DerData.cs            |  85 ++++-
 src/Renci.SshNet/Common/Extensions.cs         |   9 +
 src/Renci.SshNet/ConnectionInfo.cs            |   6 +-
 src/Renci.SshNet/PrivateKeyFile.cs            |  10 +-
 src/Renci.SshNet/Renci.SshNet.csproj          |   6 +-
 .../Cryptography/EcdsaDigitalSignature.cs     | 176 +++++++++
 .../Security/Cryptography/EcdsaKey.cs         | 360 ++++++++++++++++++
 17 files changed, 786 insertions(+), 15 deletions(-)
 create mode 100644 src/Renci.SshNet.Tests/Data/Key.ECDSA.Encrypted.txt
 create mode 100644 src/Renci.SshNet.Tests/Data/Key.ECDSA.txt
 create mode 100644 src/Renci.SshNet.Tests/Data/Key.ECDSA384.Encrypted.txt
 create mode 100644 src/Renci.SshNet.Tests/Data/Key.ECDSA384.txt
 create mode 100644 src/Renci.SshNet.Tests/Data/Key.ECDSA521.Encrypted.txt
 create mode 100644 src/Renci.SshNet.Tests/Data/Key.ECDSA521.txt
 create mode 100644 src/Renci.SshNet/Security/Cryptography/EcdsaDigitalSignature.cs
 create mode 100644 src/Renci.SshNet/Security/Cryptography/EcdsaKey.cs

diff --git a/src/Renci.SshNet.NET35/Renci.SshNet.NET35.csproj b/src/Renci.SshNet.NET35/Renci.SshNet.NET35.csproj
index a6878d187..64ee419f3 100644
--- a/src/Renci.SshNet.NET35/Renci.SshNet.NET35.csproj
+++ b/src/Renci.SshNet.NET35/Renci.SshNet.NET35.csproj
@@ -18,7 +18,7 @@
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
     <OutputPath>bin\Debug\</OutputPath>
-    <DefineConstants>TRACE;DEBUG;FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_POLL;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII</DefineConstants>
+    <DefineConstants>TRACE;DEBUG;FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_POLL;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII;FEATURE_ECDSA</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
@@ -29,7 +29,7 @@
     <DebugType>none</DebugType>
     <Optimize>true</Optimize>
     <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>TRACE;FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_POLL;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII</DefineConstants>
+    <DefineConstants>TRACE;FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_POLL;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII;FEATURE_ECDSA</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <DocumentationFile>bin\Release\Renci.SshNet.xml</DocumentationFile>
@@ -695,6 +695,12 @@
     <Compile Include="..\Renci.SshNet\Security\Cryptography\Key.cs">
       <Link>Security\Cryptography\Key.cs</Link>
     </Compile>
+    <Compile Include="..\Renci.SshNet\Security\Cryptography\EcdsaDigitalSignature.cs">
+      <Link>Security\Cryptography\EcdsaDigitalSignature.cs</Link>
+    </Compile>
+    <Compile Include="..\Renci.SshNet\Security\Cryptography\EcdsaKey.cs">
+      <Link>Security\Cryptography\EcdsaKey.cs</Link>
+    </Compile>
     <Compile Include="..\Renci.SshNet\Security\Cryptography\RsaDigitalSignature.cs">
       <Link>Security\Cryptography\RsaDigitalSignature.cs</Link>
     </Compile>
diff --git a/src/Renci.SshNet.Tests.NET35/Renci.SshNet.Tests.NET35.csproj b/src/Renci.SshNet.Tests.NET35/Renci.SshNet.Tests.NET35.csproj
index a42cf8ec1..893a6fe0c 100644
--- a/src/Renci.SshNet.Tests.NET35/Renci.SshNet.Tests.NET35.csproj
+++ b/src/Renci.SshNet.Tests.NET35/Renci.SshNet.Tests.NET35.csproj
@@ -1737,6 +1737,26 @@
       <Link>Data\Key.SSH2.RSA.txt</Link>
     </EmbeddedResource>
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="..\Renci.SshNet.Tests\Data\Key.ECDSA.txt">
+      <Link>Data\Key.ECDSA.txt</Link>
+    </EmbeddedResource>
+    <EmbeddedResource Include="..\Renci.SshNet.Tests\Data\Key.ECDSA384.txt">
+      <Link>Data\Key.ECDSA384.txt</Link>
+    </EmbeddedResource>
+    <EmbeddedResource Include="..\Renci.SshNet.Tests\Data\Key.ECDSA521.txt">
+      <Link>Data\Key.ECDSA521.txt</Link>
+    </EmbeddedResource>
+    <EmbeddedResource Include="..\Renci.SshNet.Tests\Data\Key.ECDSA.Encrypted.txt">
+      <Link>Data\Key.ECDSA.Encrypted.txt</Link>
+    </EmbeddedResource>
+    <EmbeddedResource Include="..\Renci.SshNet.Tests\Data\Key.ECDSA384.Encrypted.txt">
+      <Link>Data\Key.ECDSA384.Encrypted.txt</Link>
+    </EmbeddedResource>
+    <EmbeddedResource Include="..\Renci.SshNet.Tests\Data\Key.ECDSA521.Encrypted.txt">
+      <Link>Data\Key.ECDSA521.Encrypted.txt</Link>
+    </EmbeddedResource>
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <ProjectExtensions>
     <VisualStudio>
diff --git a/src/Renci.SshNet.Tests/Classes/PrivateKeyFileTest.cs b/src/Renci.SshNet.Tests/Classes/PrivateKeyFileTest.cs
index 21bd97853..3c944c8d4 100644
--- a/src/Renci.SshNet.Tests/Classes/PrivateKeyFileTest.cs
+++ b/src/Renci.SshNet.Tests/Classes/PrivateKeyFileTest.cs
@@ -319,6 +319,72 @@ public void Test_PrivateKey_RSA_DES_EDE3_CFB()
             }
         }
 
+        [TestMethod]
+        [Owner("darinkes")]
+        [TestCategory("PrivateKey")]
+        public void Test_PrivateKey_ECDSA()
+        {
+            using (var stream = GetData("Key.ECDSA.txt"))
+            {
+                new PrivateKeyFile(stream);
+            }
+        }
+
+        [TestMethod]
+        [Owner("darinkes")]
+        [TestCategory("PrivateKey")]
+        public void Test_PrivateKey_ECDSA384()
+        {
+            using (var stream = GetData("Key.ECDSA384.txt"))
+            {
+                new PrivateKeyFile(stream);
+            }
+        }
+
+        [TestMethod]
+        [Owner("darinkes")]
+        [TestCategory("PrivateKey")]
+        public void Test_PrivateKey_ECDSA521()
+        {
+            using (var stream = GetData("Key.ECDSA521.txt"))
+            {
+                new PrivateKeyFile(stream);
+            }
+        }
+
+        [TestMethod]
+        [Owner("darinkes")]
+        [TestCategory("PrivateKey")]
+        public void Test_PrivateKey_ECDSA_Encrypted()
+        {
+            using (var stream = GetData("Key.ECDSA.Encrypted.txt"))
+            {
+                new PrivateKeyFile(stream, "12345");
+            }
+        }
+
+        [TestMethod]
+        [Owner("darinkes")]
+        [TestCategory("PrivateKey")]
+        public void Test_PrivateKey_ECDSA384_Encrypted()
+        {
+            using (var stream = GetData("Key.ECDSA384.Encrypted.txt"))
+            {
+                new PrivateKeyFile(stream, "12345");
+            }
+        }
+
+        [TestMethod]
+        [Owner("darinkes")]
+        [TestCategory("PrivateKey")]
+        public void Test_PrivateKey_ECDSA521_Encrypted()
+        {
+            using (var stream = GetData("Key.ECDSA521.Encrypted.txt"))
+            {
+                new PrivateKeyFile(stream, "12345");
+            }
+        }
+
         /// <summary>
         ///A test for Dispose
         ///</summary>
diff --git a/src/Renci.SshNet.Tests/Data/Key.ECDSA.Encrypted.txt b/src/Renci.SshNet.Tests/Data/Key.ECDSA.Encrypted.txt
new file mode 100644
index 000000000..f0af5ba7d
--- /dev/null
+++ b/src/Renci.SshNet.Tests/Data/Key.ECDSA.Encrypted.txt
@@ -0,0 +1,8 @@
+-----BEGIN EC PRIVATE KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,54D46F498C989115AAE14FEA21E3AF11
+
+IQdFnndcbzz10d7YQIgEE1TzuzJrm7uYJr4Hvdfz/FshVxMRqxqaqtEgo2vAHHik
+BOcPkm+84ERlTNPslcJqLSkKzCdxb7Rz5hfwHuN3Y6Lf01qGakDlzAUEjEyDor+4
+zQtAne+f+gRUJnBvLLoVhH4xdeQFC55GECNUFQpEmos=
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/src/Renci.SshNet.Tests/Data/Key.ECDSA.txt b/src/Renci.SshNet.Tests/Data/Key.ECDSA.txt
new file mode 100644
index 000000000..13ac9fb49
--- /dev/null
+++ b/src/Renci.SshNet.Tests/Data/Key.ECDSA.txt
@@ -0,0 +1,5 @@
+-----BEGIN EC PRIVATE KEY-----
+MHcCAQEEIEdqaFKgJBIibVjyUh1v7Y35LwIQJrocdTaYFLwl7iB0oAoGCCqGSM49
+AwEHoUQDQgAEQD5MO/n9yqSDTszwzVpApLx5SQFecE5ZfDkgxqVdHQecm1BAPozZ
+4eKGNhKn72hT79mLlp9HXX+oNEcuVT83Hw==
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/src/Renci.SshNet.Tests/Data/Key.ECDSA384.Encrypted.txt b/src/Renci.SshNet.Tests/Data/Key.ECDSA384.Encrypted.txt
new file mode 100644
index 000000000..00072ce24
--- /dev/null
+++ b/src/Renci.SshNet.Tests/Data/Key.ECDSA384.Encrypted.txt
@@ -0,0 +1,9 @@
+-----BEGIN EC PRIVATE KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,1D64653C5E18C2AACB0B17E3FE43C219
+
+lCtRmcvKSeIACwqTtsf/ei1brtCZ386rsk/j7bSXdkZBpvzcmzbeo6w6CYm206Km
+hV9TMl2dIO/I1/ov5/2VIR3ZkaElyDOJD/+Be0e3aus4EZj1H1YM/Dv+4QJId+is
+Cw4ycWjfudYPPejGdiyjzt5qjaIJwrrEvGtMg7sWVAqDpjcAjS9KuaCu5nOgdItL
+s7oHuz+DTGdJQNfUHAlUnz1JaMRWzpP0MwtxdcaRY+w=
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/src/Renci.SshNet.Tests/Data/Key.ECDSA384.txt b/src/Renci.SshNet.Tests/Data/Key.ECDSA384.txt
new file mode 100644
index 000000000..f2d658ea4
--- /dev/null
+++ b/src/Renci.SshNet.Tests/Data/Key.ECDSA384.txt
@@ -0,0 +1,6 @@
+-----BEGIN EC PRIVATE KEY-----
+MIGkAgEBBDCQawHdHLR7NvKa2vPV0sVkbzOE8c0enp95iEysGcGV66RXE1EH//nh
+gu5UzeTR4KigBwYFK4EEACKhZANiAAQUk4rVvoOPI1hQzWpNx09Uo6qG+srGcbvB
+q15eFK0GnK/T0UBKxdbZ2+//KAYI6SeDHM9t3ORF1aX5EpjTEBI4d7ZY/lV9jX6M
+nJ4XuGteJselM2iMmy+p9ZYw83BYB1Y=
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/src/Renci.SshNet.Tests/Data/Key.ECDSA521.Encrypted.txt b/src/Renci.SshNet.Tests/Data/Key.ECDSA521.Encrypted.txt
new file mode 100644
index 000000000..381b30be8
--- /dev/null
+++ b/src/Renci.SshNet.Tests/Data/Key.ECDSA521.Encrypted.txt
@@ -0,0 +1,10 @@
+-----BEGIN EC PRIVATE KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,F995028237EBD79C928530CC6C3E957F
+
+wT+iajbte4MnpCipVy/7W9t2I8OgwbMjNBw9PB5xmXR1NQX+yWa81DXMTgjHi8++
+6tp+Vlftkr7mY1yvZCVo1Sy4VgcvZeMhtpVKtvYdMCmHJC6gaDOTYX3yee8DJ4FL
+fG+IQz0wFyZZ26NFrHiwbufW9z6pXhGNCQZK0KLbFxI9iKwVA0llc7uzTEcmBBpn
+0/Snp0CVvX+i6AP9Xj0bBdrFCsvcoT+ZHzS8YWJUfu3m6cpAJksCAy0PXR3ifvus
+edTfDpkMxd4/b+DtPB6SMekIAjnQyzbyaTwJCujm8iU=
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/src/Renci.SshNet.Tests/Data/Key.ECDSA521.txt b/src/Renci.SshNet.Tests/Data/Key.ECDSA521.txt
new file mode 100644
index 000000000..31abe917a
--- /dev/null
+++ b/src/Renci.SshNet.Tests/Data/Key.ECDSA521.txt
@@ -0,0 +1,7 @@
+-----BEGIN EC PRIVATE KEY-----
+MIHcAgEBBEIBn2DAme7AU8sCA+/sd6s3c2FNW26IiPvulGd3FC8k5q+fjBZ5LUWR
+iJMGrsf2rJLO8hXMGJYoF9tjZEGaabQ8KVagBwYFK4EEACOhgYkDgYYABABrpVjs
+ANqcvqMUo1wo0I1uVCXQ6xrauy4iU86FiOwFmkYRrle4w3oYdRJwniC3TwGMuBuM
+PMIoCTXr0UtUzn1vkQESNR/J/jAxVseLlVe+KDfZHKvsvk2+O4XaSa1qMfLwN3sp
+wlj08+ylKjlO6V3g0hbz4ZaSVwuiRS7Xsv8W2MV6rg==
+-----END EC PRIVATE KEY-----
\ No newline at end of file
diff --git a/src/Renci.SshNet.Tests/Renci.SshNet.Tests.csproj b/src/Renci.SshNet.Tests/Renci.SshNet.Tests.csproj
index d968dd27b..6f64c0048 100644
--- a/src/Renci.SshNet.Tests/Renci.SshNet.Tests.csproj
+++ b/src/Renci.SshNet.Tests/Renci.SshNet.Tests.csproj
@@ -709,6 +709,14 @@
       <Name>Renci.SshNet</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <EmbeddedResource Include="Data\Key.ECDSA.txt" />
+    <EmbeddedResource Include="Data\Key.ECDSA384.txt" />
+    <EmbeddedResource Include="Data\Key.ECDSA521.txt" />
+    <EmbeddedResource Include="Data\Key.ECDSA.Encrypted.txt" />
+    <EmbeddedResource Include="Data\Key.ECDSA384.Encrypted.txt" />
+    <EmbeddedResource Include="Data\Key.ECDSA521.Encrypted.txt" />
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
diff --git a/src/Renci.SshNet/Common/DerData.cs b/src/Renci.SshNet/Common/DerData.cs
index c84c0b176..59c93a11f 100644
--- a/src/Renci.SshNet/Common/DerData.cs
+++ b/src/Renci.SshNet/Common/DerData.cs
@@ -12,7 +12,7 @@ public class DerData
 
         private const byte Boolean = 0x01;
         private const byte Integer = 0x02;
-        //private const byte BITSTRING = 0x03;
+        private const byte BITSTRING = 0x03;
         private const byte Octetstring = 0x04;
         private const byte Null = 0x05;
         private const byte Objectidentifier = 0x06;
@@ -101,7 +101,7 @@ public BigInteger ReadBigInteger()
         {
             var type = ReadByte();
             if (type != Integer)
-                throw new InvalidOperationException("Invalid data type, INTEGER(02) is expected.");
+                throw new InvalidOperationException(string.Format("Invalid data type, INTEGER(02) is expected, got {0}", type));
 
             var length = ReadLength();
 
@@ -118,7 +118,7 @@ public int ReadInteger()
         {
             var type = ReadByte();
             if (type != Integer)
-                throw new InvalidOperationException("Invalid data type, INTEGER(02) is expected.");
+                throw new InvalidOperationException(string.Format("Invalid data type, INTEGER(02) is expected, got {0}", type));
 
             var length = ReadLength();
 
@@ -140,6 +140,36 @@ public int ReadInteger()
             return result;
         }
 
+        /// <summary>
+        /// Reads next octetstring data type from internal buffer.
+        /// </summary>
+        /// <returns>data read.</returns>
+        public byte[] ReadOctetString()
+        {
+            var type = ReadByte();
+            if (type != Octetstring)
+                throw new InvalidOperationException(string.Format("Invalid data type, OCTETSTRING(04) is expected, got {0}", type));
+
+            var length = ReadLength();
+            var data = ReadBytes(length);
+            return data;
+        }
+
+        /// <summary>
+        /// Reads next object data type from internal buffer.
+        /// </summary>
+        /// <returns>data read.</returns>
+        public byte[] ReadObject()
+        {
+            var type = ReadByte();
+            if (type != Objectidentifier)
+                throw new InvalidOperationException(string.Format("Invalid data type, OBJECT(06) is expected, got {0}", type));
+
+            var length = ReadLength();
+            var data = ReadBytes(length);
+            return data;
+        }
+
         /// <summary>
         /// Writes BOOLEAN data into internal buffer.
         /// </summary>
@@ -189,6 +219,18 @@ public void Write(byte[] data)
             WriteBytes(data);
         }
 
+        /// <summary>
+        /// Writes BITSTRING data into internal buffer.
+        /// </summary>
+        /// <param name="data">The data.</param>
+        public void WriteBitstring(byte[] data)
+        {
+            _data.Add(BITSTRING);
+            var length = GetLength(data.Length);
+            WriteBytes(length);
+            WriteBytes(data);
+        }
+
         /// <summary>
         /// Writes OBJECTIDENTIFIER data into internal buffer.
         /// </summary>
@@ -229,6 +271,18 @@ public void Write(ObjectIdentifier identifier)
             WriteBytes(bytes);
         }
 
+        /// <summary>
+        /// Writes OBJECTIDENTIFIER data into internal buffer.
+        /// </summary>
+        /// <param name="bytes">The bytes.</param>
+        public void WriteObjectIdentifier(byte[] bytes)
+        {
+            _data.Add(Objectidentifier);
+            var length = GetLength(bytes.Length);
+            WriteBytes(length);
+            WriteBytes(bytes);
+        }
+
         /// <summary>
         /// Writes NULL data into internal buffer.
         /// </summary>
@@ -270,8 +324,11 @@ private static IEnumerable<byte> GetLength(int length)
             }
             return new[] {(byte) length};
         }
-
-        private int ReadLength()
+        /// <summary>
+        /// Gets Data Length
+        /// </summary>
+        /// <returns>length</returns>
+        public int ReadLength()
         {
             int length = ReadByte();
 
@@ -306,12 +363,19 @@ private int ReadLength()
             return length;
         }
 
-        private void WriteBytes(IEnumerable<byte> data)
+        /// <summary>
+        /// Write Byte data into internal buffer.
+        /// </summary>
+        public void WriteBytes(IEnumerable<byte> data)
         {
             _data.AddRange(data);
         }
 
-        private byte ReadByte()
+        /// <summary>
+        /// Reads Byte data into internal buffer.
+        /// </summary>
+        /// <returns>data read</returns>
+        public byte ReadByte()
         {
             if (_readerIndex > _data.Count)
                 throw new InvalidOperationException("Read out of boundaries.");
@@ -319,7 +383,12 @@ private byte ReadByte()
             return _data[_readerIndex++];
         }
 
-        private byte[] ReadBytes(int length)
+        /// <summary>
+        /// Reads lengths Bytes data into internal buffer.
+        /// </summary>
+        /// <returns>data read</returns>
+        ///  <param name="length">amount of data to read.</param>
+        public byte[] ReadBytes(int length)
         {
             if (_readerIndex + length > _data.Count)
                 throw new InvalidOperationException("Read out of boundaries.");
diff --git a/src/Renci.SshNet/Common/Extensions.cs b/src/Renci.SshNet/Common/Extensions.cs
index 9d163bc96..384687bf3 100644
--- a/src/Renci.SshNet/Common/Extensions.cs
+++ b/src/Renci.SshNet/Common/Extensions.cs
@@ -247,6 +247,15 @@ public static byte[] TrimLeadingZeros(this byte[] value)
             return value;
         }
 
+        public static byte[] Pad(this byte[] data, int length)
+        {
+            if (length <= data.Length)
+                return data;
+            var new_data = new byte[length];
+            Buffer.BlockCopy(data, 0, new_data, new_data.Length - data.Length, data.Length);
+            return new_data;
+        }
+
         public static byte[] Concat(this byte[] first, byte[] second)
         {
             if (first == null || first.Length == 0)
diff --git a/src/Renci.SshNet/ConnectionInfo.cs b/src/Renci.SshNet/ConnectionInfo.cs
index a8317909a..26ca884df 100644
--- a/src/Renci.SshNet/ConnectionInfo.cs
+++ b/src/Renci.SshNet/ConnectionInfo.cs
@@ -378,9 +378,13 @@ public ConnectionInfo(string host, int port, string username, ProxyTypes proxyTy
 
             HostKeyAlgorithms = new Dictionary<string, Func<byte[], KeyHostAlgorithm>>
                 {
+#if FEATURE_ECDSA
+                    {"ecdsa-sha2-nistp256", data => new KeyHostAlgorithm("ecdsa-sha2-nistp256", new EcdsaKey(), data)},
+                    {"ecdsa-sha2-nistp384", data => new KeyHostAlgorithm("ecdsa-sha2-nistp384", new EcdsaKey(), data)},
+                    {"ecdsa-sha2-nistp521", data => new KeyHostAlgorithm("ecdsa-sha2-nistp521", new EcdsaKey(), data)},
+#endif
                     {"ssh-rsa", data => new KeyHostAlgorithm("ssh-rsa", new RsaKey(), data)},
                     {"ssh-dss", data => new KeyHostAlgorithm("ssh-dss", new DsaKey(), data)},
-                    //{"ecdsa-sha2-nistp256 "}
                     //{"x509v3-sign-rsa", () => { ... },
                     //{"x509v3-sign-dss", () => { ... },
                     //{"spki-sign-rsa", () => { ... },
diff --git a/src/Renci.SshNet/PrivateKeyFile.cs b/src/Renci.SshNet/PrivateKeyFile.cs
index f44672347..de3b49a7f 100644
--- a/src/Renci.SshNet/PrivateKeyFile.cs
+++ b/src/Renci.SshNet/PrivateKeyFile.cs
@@ -197,6 +197,12 @@ private void Open(Stream privateKey, string passPhrase)
                     _key = new DsaKey(decryptedData);
                     HostKey = new KeyHostAlgorithm("ssh-dss", _key);
                     break;
+#if FEATURE_ECDSA
+                case "EC":
+                    _key = new EcdsaKey(decryptedData);
+                    HostKey = new KeyHostAlgorithm(_key.ToString(), _key);
+                    break;
+#endif
                 case "SSH2 ENCRYPTED":
                     var reader = new SshDataReader(decryptedData);
                     var magicNumber = reader.ReadUInt32();
@@ -341,7 +347,7 @@ private static byte[] DecryptKey(CipherInfo cipherInfo, byte[] cipherData, strin
             return cipher.Decrypt(cipherData);
         }
 
-        #region IDisposable Members
+#region IDisposable Members
 
         private bool _isDisposed;
 
@@ -385,7 +391,7 @@ protected virtual void Dispose(bool disposing)
             Dispose(false);
         }
 
-        #endregion
+#endregion
 
         private class SshDataReader : SshData
         {
diff --git a/src/Renci.SshNet/Renci.SshNet.csproj b/src/Renci.SshNet/Renci.SshNet.csproj
index 0c3ea524b..e2d94eee7 100644
--- a/src/Renci.SshNet/Renci.SshNet.csproj
+++ b/src/Renci.SshNet/Renci.SshNet.csproj
@@ -18,7 +18,7 @@
     <DebugType>full</DebugType>
     <Optimize>false</Optimize>
     <OutputPath>bin\Debug\</OutputPath>
-    <DefineConstants>TRACE;DEBUG;FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_SELECT;FEATURE_SOCKET_POLL;FEATURE_SOCKET_DISPOSE;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_COUNTDOWNEVENT;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_WAITHANDLE_DISPOSE;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII</DefineConstants>
+    <DefineConstants>TRACE;DEBUG;FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_SELECT;FEATURE_SOCKET_POLL;FEATURE_SOCKET_DISPOSE;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_COUNTDOWNEVENT;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_WAITHANDLE_DISPOSE;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII;FEATURE_ECDSA</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <DocumentationFile>bin\Debug\Renci.SshNet.xml</DocumentationFile>
@@ -29,7 +29,7 @@
     <DebugType>none</DebugType>
     <Optimize>true</Optimize>
     <OutputPath>bin\Release\</OutputPath>
-    <DefineConstants>FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_SELECT;FEATURE_SOCKET_POLL;FEATURE_SOCKET_DISPOSE;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_COUNTDOWNEVENT;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_WAITHANDLE_DISPOSE;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII</DefineConstants>
+    <DefineConstants>FEATURE_REGEX_COMPILE;FEATURE_BINARY_SERIALIZATION;FEATURE_RNG_CREATE;FEATURE_SOCKET_SYNC;FEATURE_SOCKET_EAP;FEATURE_SOCKET_APM;FEATURE_SOCKET_SETSOCKETOPTION;FEATURE_SOCKET_SELECT;FEATURE_SOCKET_POLL;FEATURE_SOCKET_DISPOSE;FEATURE_STREAM_APM;FEATURE_DNS_SYNC;FEATURE_THREAD_COUNTDOWNEVENT;FEATURE_THREAD_THREADPOOL;FEATURE_THREAD_SLEEP;FEATURE_WAITHANDLE_DISPOSE;FEATURE_HASH_MD5;FEATURE_HASH_SHA1_CREATE;FEATURE_HASH_SHA256_CREATE;FEATURE_HASH_SHA384_CREATE;FEATURE_HASH_SHA512_CREATE;FEATURE_HASH_RIPEMD160_CREATE;FEATURE_HMAC_MD5;FEATURE_HMAC_SHA1;FEATURE_HMAC_SHA256;FEATURE_HMAC_SHA384;FEATURE_HMAC_SHA512;FEATURE_HMAC_RIPEMD160;FEATURE_MEMORYSTREAM_GETBUFFER;FEATURE_DIAGNOSTICS_TRACESOURCE;FEATURE_ENCODING_ASCII;FEATURE_ECDSA</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
     <DocumentationFile>bin\Release\Renci.SshNet.xml</DocumentationFile>
@@ -434,6 +434,8 @@
     <Compile Include="Security\Chaos.NaCl\Internal\Sha512Internal.cs" />
     <Compile Include="Security\Chaos.NaCl\MontgomeryCurve25519.cs" />
     <Compile Include="Security\Chaos.NaCl\Sha512.cs" />
+    <Compile Include="Security\Cryptography\EcdsaDigitalSignature.cs" />
+    <Compile Include="Security\Cryptography\EcdsaKey.cs" />
     <Compile Include="Security\Cryptography\HMACMD5.cs" />
     <Compile Include="Security\Cryptography\HMACSHA1.cs" />
     <Compile Include="Security\Cryptography\HMACSHA256.cs" />
diff --git a/src/Renci.SshNet/Security/Cryptography/EcdsaDigitalSignature.cs b/src/Renci.SshNet/Security/Cryptography/EcdsaDigitalSignature.cs
new file mode 100644
index 000000000..4b30b0d70
--- /dev/null
+++ b/src/Renci.SshNet/Security/Cryptography/EcdsaDigitalSignature.cs
@@ -0,0 +1,176 @@
+#if FEATURE_ECDSA
+using System;
+using Renci.SshNet.Common;
+using System.Globalization;
+
+namespace Renci.SshNet.Security.Cryptography
+{
+    /// <summary>
+    /// Implements ECDSA digital signature algorithm.
+    /// </summary>
+    public class EcdsaDigitalSignature : DigitalSignature, IDisposable
+    {
+        private readonly EcdsaKey _key;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EcdsaDigitalSignature" /> class.
+        /// </summary>
+        /// <param name="key">The ECDSA key.</param>
+        /// <exception cref="ArgumentNullException"><paramref name="key"/> is <c>null</c>.</exception>
+        public EcdsaDigitalSignature(EcdsaKey key)
+        {
+            if (key == null)
+                throw new ArgumentNullException("key");
+
+            _key = key;
+        }
+
+        /// <summary>
+        /// Verifies the signature.
+        /// </summary>
+        /// <param name="input">The input.</param>
+        /// <param name="signature">The signature.</param>
+        /// <returns>
+        /// <c>true</c> if signature was successfully verified; otherwise <c>false</c>.
+        /// </returns>
+        public override bool Verify(byte[] input, byte[] signature)
+        {
+            // for 521 sig_size is 132
+            var sig_size = _key.dsa.KeySize == 521 ? 132 : _key.dsa.KeySize / 4;
+            var ssh_data = new SshDataSignature(signature, sig_size);
+            return _key.dsa.VerifyData(input, ssh_data.Signature);
+        }
+
+        /// <summary>
+        /// Creates the signature.
+        /// </summary>
+        /// <param name="input">The input.</param>
+        /// <returns>
+        /// Signed input data.
+        /// </returns>
+        public override byte[] Sign(byte[] input)
+        {
+            var signed = _key.dsa.SignData(input);
+            var ssh_data = new SshDataSignature(signed.Length);
+            ssh_data.Signature = signed;
+            return ssh_data.GetBytes();
+        }
+
+        #region IDisposable Members
+
+        private bool _isDisposed;
+
+        /// <summary>
+        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases unmanaged and - optionally - managed resources
+        /// </summary>
+        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (_isDisposed)
+                return;
+
+            if (disposing)
+            {
+                _isDisposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Releases unmanaged resources and performs other cleanup operations before the
+        /// <see cref="EcdsaDigitalSignature"/> is reclaimed by garbage collection.
+        /// </summary>
+        ~EcdsaDigitalSignature()
+        {
+            Dispose(false);
+        }
+
+        #endregion
+    }
+
+    class SshDataSignature : SshData
+    {
+        private int _signature_size;
+
+        private byte[] _signature_r;
+        private byte[] _signature_s;
+
+        public byte[] Signature
+        {
+            get
+            {
+                var signature = new byte[_signature_size];
+                Buffer.BlockCopy(_signature_r, 0, signature, 0, _signature_r.Length);
+                Buffer.BlockCopy(_signature_s, 0, signature, _signature_r.Length, _signature_s.Length);
+                return signature;
+            }
+            set
+            {
+                var signed_r = new byte[_signature_size / 2];
+                Buffer.BlockCopy(value, 0, signed_r, 0, signed_r.Length);
+                _signature_r = BigInteger.SshFormatBignum2(signed_r).ToByteArray().Reverse();
+
+                var signed_s = new byte[_signature_size / 2];
+                Buffer.BlockCopy(value, signed_r.Length, signed_s, 0, signed_s.Length);
+                _signature_s = BigInteger.SshFormatBignum2(signed_s).ToByteArray().Reverse();
+            }
+        }
+
+        public SshDataSignature(int sig_size)
+        {
+            _signature_size = sig_size;
+        }
+
+        public SshDataSignature(byte[] data, int sig_size)
+        {
+            _signature_size = sig_size;
+            Load(data);
+        }
+
+        protected override void LoadData()
+        {
+            _signature_r = ReadBinary().TrimLeadingZeros().Pad(_signature_size / 2);
+            _signature_s = ReadBinary().TrimLeadingZeros().Pad(_signature_size / 2);
+        }
+
+        protected override void SaveData()
+        {
+            WriteBinaryString(BigInteger.SshFormatBignum2(_signature_r).ToByteArray().Reverse());
+            WriteBinaryString(BigInteger.SshFormatBignum2(_signature_s).ToByteArray().Reverse());
+        }
+
+        public new byte[] ReadBinary()
+        {
+            var length = ReadUInt32();
+
+            if (length > int.MaxValue)
+            {
+                throw new NotSupportedException(string.Format(CultureInfo.CurrentCulture, "Strings longer than {0} is not supported.", int.MaxValue));
+            }
+
+            return ReadBytes((int)length);
+        }
+
+        protected override int BufferCapacity
+        {
+            get
+            {
+                var capacity = base.BufferCapacity;
+                capacity += 4; // r length
+                capacity += _signature_r.Length; // signature r
+                capacity += 4; // s length
+                capacity += _signature_s.Length; // signature s
+                return capacity;
+            }
+        }
+    }
+}
+#endif
\ No newline at end of file
diff --git a/src/Renci.SshNet/Security/Cryptography/EcdsaKey.cs b/src/Renci.SshNet/Security/Cryptography/EcdsaKey.cs
new file mode 100644
index 000000000..4c1f52dda
--- /dev/null
+++ b/src/Renci.SshNet/Security/Cryptography/EcdsaKey.cs
@@ -0,0 +1,360 @@
+#if FEATURE_ECDSA
+using System;
+using System.IO;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
+using Renci.SshNet.Common;
+using Renci.SshNet.Security.Cryptography;
+
+namespace Renci.SshNet.Security
+{
+    /// <summary>
+    /// Contains ECDSA (ecdsa-sha2-nistp{256,384,521}) private and public key
+    /// </summary>
+    public class EcdsaKey : Key, IDisposable
+    {
+        internal enum KeyBlobMagicNumber : int
+        {
+            BCRYPT_ECDSA_PUBLIC_P256_MAGIC = 0x31534345,
+            BCRYPT_ECDSA_PRIVATE_P256_MAGIC = 0x32534345,
+            BCRYPT_ECDSA_PUBLIC_P384_MAGIC = 0x33534345,
+            BCRYPT_ECDSA_PRIVATE_P384_MAGIC = 0x34534345,
+            BCRYPT_ECDSA_PUBLIC_P521_MAGIC = 0x35534345,
+            BCRYPT_ECDSA_PRIVATE_P521_MAGIC = 0x36534345,
+
+            BCRYPT_ECDH_PUBLIC_P256_MAGIC = 0x314B4345,
+            BCRYPT_ECDH_PRIVATE_P256_MAGIC = 0x324B4345,
+            BCRYPT_ECDH_PUBLIC_P384_MAGIC = 0x334B4345,
+            BCRYPT_ECDH_PRIVATE_P384_MAGIC = 0x344B4345,
+            BCRYPT_ECDH_PUBLIC_P521_MAGIC = 0x354B4345,
+            BCRYPT_ECDH_PRIVATE_P521_MAGIC = 0x364B4345,
+
+            BCRYPT_ECDH_PUBLIC_GENERIC_MAGIC = 0x504B4345,
+            BCRYPT_ECDH_PRIVATE_GENERIC_MAGIC = 0x564B4345,
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct BCRYPT_ECCKEY_BLOB
+        {
+            internal KeyBlobMagicNumber Magic;
+            internal int cbKey;
+        }
+
+        /// <summary>
+        /// Gets dsa
+        /// </summary>
+        public ECDsaCng dsa;
+
+        private CngKey key;
+
+        /// <summary>
+        /// Gets the SSH name of the ECDSA Key
+        /// </summary>
+        public override string ToString()
+        {
+            return string.Format("ecdsa-sha2-nistp{0}", KeyLength);
+        }
+
+        /// <summary>
+        /// Gets the length of the key.
+        /// </summary>
+        /// <value>
+        /// The length of the key.
+        /// </value>
+        public override int KeyLength
+        {
+            get
+            {
+                return key.KeySize;
+            }
+        }
+
+        /// <summary>
+        /// Gets the digital signature.
+        /// </summary>
+        protected override DigitalSignature DigitalSignature
+        {
+            get
+            {
+                if (_digitalSignature == null)
+                {
+                    _digitalSignature = new EcdsaDigitalSignature(this);
+                }
+                return _digitalSignature;
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets the public.
+        /// </summary>
+        /// <value>
+        /// The public.
+        /// </value>
+        public override BigInteger[] Public
+        {
+            get
+            {
+                var blob = key.Export(CngKeyBlobFormat.EccPublicBlob);
+
+                byte[] qx;
+                byte[] qy;
+                KeyBlobMagicNumber magic;
+                using (var br = new BinaryReader(new MemoryStream(blob)))
+                {
+                    magic = (KeyBlobMagicNumber)br.ReadInt32();
+                    int cbKey = br.ReadInt32();
+                    qx = br.ReadBytes(cbKey);
+                    qy = br.ReadBytes(cbKey);
+                }
+
+                string curve = "";
+                switch (magic)
+                {
+                    case KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_P256_MAGIC:
+                        curve = "nistp256";
+                        break;
+                    case KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_P384_MAGIC:
+                        curve = "nistp384";
+                        break;
+                    case KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_P521_MAGIC:
+                        curve = "nistp521";
+                        break;
+                    default:
+                        throw new SshException("Unexpected Curve Magic: " + magic);
+                }
+                var curve_bn = new BigInteger(Encoding.ASCII.GetBytes(curve).Reverse());
+
+                // Make ECPoint from x and y
+                // Prepend 04 (uncompressed format) + qx-bytes + qy-bytes
+                var point_bn_bytes = new byte[1 + qx.Length + qy.Length];
+                Buffer.SetByte(point_bn_bytes, 0, 4);
+                Buffer.BlockCopy(qx, 0, point_bn_bytes, 1, qx.Length);
+                Buffer.BlockCopy(qy, 0, point_bn_bytes, qx.Length + 1, qy.Length);
+
+                // returns Curve-Name and x/y as ECPoint
+                return new[] { curve_bn, new BigInteger(point_bn_bytes.Reverse()) };
+            }
+            set
+            {
+                // value[0]:
+                // Curve Name as String
+                // nistp{256,384,521}
+                var value_0 = Encoding.ASCII.GetString(value[0].ToByteArray().Reverse()); // Curve Name as String
+
+                var curve_magic = KeyBlobMagicNumber.BCRYPT_ECDH_PRIVATE_GENERIC_MAGIC;
+                var hash_algo = CngAlgorithm.Sha256;
+                switch (value_0)
+                {
+                    case "nistp256":
+                        curve_magic = KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_P256_MAGIC;
+                        hash_algo = CngAlgorithm.Sha256;
+                        break;
+                    case "nistp384":
+                        curve_magic = KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_P384_MAGIC;
+                        hash_algo = CngAlgorithm.Sha384;
+                        break;
+                    case "nistp521":
+                        curve_magic = KeyBlobMagicNumber.BCRYPT_ECDSA_PUBLIC_P521_MAGIC;
+                        hash_algo = CngAlgorithm.Sha512;
+                        break;
+                    default:
+                        throw new SshException("Unexpected Curve Name: " + value_0);
+                }
+
+                // ECPoint as BigInteger(2)
+                var value_1 = value[1].ToByteArray().Reverse();
+
+                var cord_size = (value_1.Length - 1) / 2;
+                var value_1_x = new byte[cord_size];
+                Buffer.BlockCopy(value_1, 1, value_1_x, 0, value_1_x.Length); // first byte is format. should be checked?
+
+                var value_1_y = new byte[cord_size];
+                Buffer.BlockCopy(value_1, cord_size + 1, value_1_y, 0, value_1_y.Length);
+
+                int headerSize = Marshal.SizeOf(typeof(BCRYPT_ECCKEY_BLOB));
+                int blobSize = headerSize + (2 * cord_size);
+                byte[] blob = new byte[blobSize];
+
+                using (var bw = new BinaryWriter(new MemoryStream(blob)))
+                {
+                    bw.Write((int)curve_magic);
+                    bw.Write(cord_size);
+                    bw.Write(value_1_x); // q.x
+                    bw.Write(value_1_y); // q.y
+                }
+                key = CngKey.Import(blob, CngKeyBlobFormat.EccPublicBlob);
+                dsa = new ECDsaCng(key)
+                {
+                    HashAlgorithm = hash_algo
+                };
+            }
+        }
+
+        private EcdsaDigitalSignature _digitalSignature;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EcdsaKey"/> class.
+        /// </summary>
+        public EcdsaKey()
+        {
+        }
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="EcdsaKey"/> class.
+        /// </summary>
+        /// <param name="data">DER encoded private key data.</param>
+        public EcdsaKey(byte[] data)
+        {
+            var der = new DerData(data);
+            var version = der.ReadBigInteger(); // skip version
+
+            // PrivateKey
+            var privatekey = der.ReadOctetString();
+
+            // Construct
+            var s0 = der.ReadByte();
+            if ((s0 & 0xe0) != 0xa0)
+                throw new SshException(string.Format("UnexpectedDER: wanted constructed tag (0xa0-0xbf), got: {0:X}", s0));
+            var tag = s0 & 0x1f;
+            if (tag != 0)
+                throw new SshException(string.Format("expected tag 0 in DER privkey, got: {0}", tag));
+            der.ReadByte(); // object length
+
+            // curve OID
+            var curve = der.ReadObject();
+
+            var pkcs8_data = PemToPkcs8(privatekey, curve, true);
+            key = ImportPkcs8(pkcs8_data, privatekey);
+            dsa = new ECDsaCng(key);
+
+            switch (dsa.KeySize)
+            {
+                case 256:
+                    dsa.HashAlgorithm = CngAlgorithm.Sha256;
+                    break;
+                case 384:
+                    dsa.HashAlgorithm = CngAlgorithm.Sha384;
+                    break;
+                case 521:
+                    dsa.HashAlgorithm = CngAlgorithm.Sha512;
+                    break;
+                default:
+                    throw new SshException("Unknown KeySize: " + dsa.KeySize);
+            }
+        }
+
+        private CngKey ImportPkcs8(byte[] pkcs8_data, byte[] privatekey)
+        {
+            // There was an issue in older .NET Versions which prevents
+            // the usage our keys. Was fixed with .NET 4.6.1. Workaround:
+            // Change KeyBlobMagicNumber from Key-exchange (ECDH) to Signing (ECDSA)
+            // See: https://stackoverflow.com/a/43982666
+            var key =CngKey.Import(pkcs8_data, CngKeyBlobFormat.Pkcs8PrivateBlob);
+
+            var blob = key.Export(CngKeyBlobFormat.EccPublicBlob);
+            key.Dispose();
+            byte[] qx;
+            byte[] qy;
+            KeyBlobMagicNumber magic;
+            int cbkey;
+            using (var br = new BinaryReader(new MemoryStream(blob)))
+            {
+                magic = (KeyBlobMagicNumber)br.ReadInt32();
+                cbkey = br.ReadInt32();
+                qx = br.ReadBytes(cbkey);
+                qy = br.ReadBytes(cbkey);
+            }
+
+            switch (magic)
+            {
+                case KeyBlobMagicNumber.BCRYPT_ECDH_PUBLIC_P256_MAGIC:
+                    magic = KeyBlobMagicNumber.BCRYPT_ECDSA_PRIVATE_P256_MAGIC;
+                    break;
+                case KeyBlobMagicNumber.BCRYPT_ECDH_PUBLIC_P384_MAGIC:
+                    magic = KeyBlobMagicNumber.BCRYPT_ECDSA_PRIVATE_P384_MAGIC;
+                    break;
+                case KeyBlobMagicNumber.BCRYPT_ECDH_PUBLIC_P521_MAGIC:
+                    magic = KeyBlobMagicNumber.BCRYPT_ECDSA_PRIVATE_P521_MAGIC;
+                    break;
+            }
+
+            int headerSize = Marshal.SizeOf(typeof(BCRYPT_ECCKEY_BLOB));
+            int blobSize = headerSize + qx.Length + qy.Length + privatekey.Length;
+            byte[] new_blob = new byte[blobSize];
+
+            using (var bw = new BinaryWriter(new MemoryStream(new_blob)))
+            {
+                bw.Write((int)magic);
+                bw.Write(cbkey);
+                bw.Write(qx); // q.x
+                bw.Write(qy); // q.y
+                bw.Write(privatekey); // d
+            }
+            return CngKey.Import(new_blob, CngKeyBlobFormat.EccPrivateBlob);
+        }
+
+        // Since Windows Crypto API is unable to parse/read our PEM format directly
+        // we have to convert it to PKCS#8 Format first
+        private byte[] PemToPkcs8(byte[] key, byte[] curve, bool isprivate)
+        {
+            var newdata = new DerData();
+            newdata.Write(new BigInteger(0));
+
+            // Create Infos about Content and our Curve
+            var objdata = new DerData();
+            // 1.2.840.10045.2.1 - ECDSA and ECDH Public Key.
+            var obj = new ObjectIdentifier(1, 2, 840, 10045, 2, 1);
+            objdata.Write(obj);
+            objdata.WriteObjectIdentifier(curve);
+            newdata.WriteBytes(objdata.Encode());
+
+            var keydata = new DerData();
+            keydata.Write(new BigInteger(isprivate ? 1: 0));
+            keydata.Write(key);
+
+            newdata.Write(keydata.Encode());
+
+            return newdata.Encode();
+        }
+        #region IDisposable Members
+
+        private bool _isDisposed;
+
+        /// <summary>
+        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
+        /// </summary>
+        public void Dispose()
+        {
+            Dispose(true);
+            GC.SuppressFinalize(this);
+        }
+
+        /// <summary>
+        /// Releases unmanaged and - optionally - managed resources
+        /// </summary>
+        /// <param name="disposing"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
+        protected virtual void Dispose(bool disposing)
+        {
+            if (_isDisposed)
+                return;
+
+            if (disposing)
+            {
+                _isDisposed = true;
+            }
+        }
+
+        /// <summary>
+        /// Releases unmanaged resources and performs other cleanup operations before the
+        /// <see cref="DsaKey"/> is reclaimed by garbage collection.
+        /// </summary>
+        ~EcdsaKey()
+        {
+            Dispose(false);
+        }
+
+        #endregion
+    }
+}
+#endif
\ No newline at end of file