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Add support for X25519DiffieHellman from BCL on .NET 11.0+ and .NET FW #1833

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Add support for X25519DiffieHellman from BCL on .NET 11.0+ and .NET FW #1833

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d0961a7
Add support for X25519DiffieHellman from BCL on .NET 11.0+ and .NET F…
scott-xu Aug 25, 2026
d4f929a
Update Microsoft.Bcl.Cryptography to 11.0.0
scott-xu Nov 10, 2026
fa7d4b8
Merge branch 'develop' into bcl-x25519dh
scott-xu Nov 10, 2026
7989a2d
Merge branch 'develop' into bcl-x25519dh
scott-xu Nov 15, 2026
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4 changes: 1 addition & 3 deletions Directory.Packages.props
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Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,7 @@
<PackageVersion Include="coverlet.msbuild" Version="10.1.0" />
<PackageVersion Include="GitHubActionsTestLogger" Version="3.0.5" />
<PackageVersion Include="Meziantou.Analyzer" Version="3.0.317" />
<!-- Should stay on LTS .NET releases. -->
<PackageVersion Include="Microsoft.Bcl.Cryptography" Version="10.0.15" />
<PackageVersion Include="Microsoft.Bcl.Cryptography" Version="11.0.0" />
<PackageVersion Include="Microsoft.Extensions.Logging.Abstractions" Version="8.0.3" />
<PackageVersion Include="Microsoft.Extensions.Logging.Console" Version="10.0.15" />
<PackageVersion Include="MSTest" Version="4.5.2" />
Expand All @@ -20,7 +19,6 @@
<PackageVersion Include="PolySharp" Version="1.16.0" />
<PackageVersion Include="SonarAnalyzer.CSharp" Version="10.35.0.4138" />
<PackageVersion Include="StyleCop.Analyzers" Version="1.2.0-beta.556" />
<!-- Should stay on LTS .NET releases. -->
<PackageVersion Include="System.Formats.Asn1" Version="10.0.15" />
<PackageVersion Include="Testcontainers" Version="4.16.0" />
</ItemGroup>
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2 changes: 1 addition & 1 deletion src/Renci.SshNet/Security/KeyExchangeECCurve25519.BclImpl.cs
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@@ -1,4 +1,4 @@
#if NET
#if NET && !NET11_0_OR_GREATER

@Rob-Hague Rob-Hague Nov 14, 2026

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this can be #if NET10_0 after #1837 (same in other places). Can we call it KeyExchangeECCurve25519.net10.cs

@scott-xu scott-xu Nov 15, 2026

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Will update once #1837 is merged.

using System.Security.Cryptography;

namespace Renci.SshNet.Security
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41 changes: 41 additions & 0 deletions src/Renci.SshNet/Security/KeyExchangeECCurve25519.BclImpl2.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,41 @@
#if NETFRAMEWORK || NET11_0_OR_GREATER
using System.Security.Cryptography;

namespace Renci.SshNet.Security
{
internal partial class KeyExchangeECCurve25519
{
protected sealed class BclImpl : Impl
{
private readonly X25519DiffieHellman _clientX25519DH;

public BclImpl()
{
_clientX25519DH = X25519DiffieHellman.GenerateKey();
}

public override byte[] GenerateClientPublicKey()
{
return _clientX25519DH.ExportPublicKey();
}

public override byte[] CalculateAgreement(byte[] serverPublicKey)
{
using var serverX25519DH = X25519DiffieHellman.ImportPublicKey(serverPublicKey);

return _clientX25519DH.DeriveRawSecretAgreement(serverX25519DH.ExportPublicKey());
}

protected override void Dispose(bool disposing)
{
base.Dispose(disposing);

if (disposing)
{
_clientX25519DH.Dispose();
}
}
}
}
}
#endif
14 changes: 10 additions & 4 deletions src/Renci.SshNet/Security/KeyExchangeECCurve25519.cs
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Expand Up @@ -8,10 +8,10 @@ namespace Renci.SshNet.Security
internal partial class KeyExchangeECCurve25519 : KeyExchangeEC
{
#pragma warning disable SA1401 // Fields should be private
#if NET
protected Impl _impl;
#else
#if NETSTANDARD
protected BouncyCastleImpl _impl;
#else
protected Impl _impl;
#endif
#pragma warning restore SA1401 // Fields should be private

Expand All @@ -38,12 +38,18 @@ protected override int HashSize
public override void Start(Session session, KeyExchangeInitMessage message, bool sendClientInitMessage)
{
base.Start(session, message, sendClientInitMessage);
#if NET
#if NET && !NET11_0_OR_GREATER
if (System.OperatingSystem.IsWindowsVersionAtLeast(10))
{
_impl = new BclImpl();
}
else
#elif NETFRAMEWORK || NET11_0_OR_GREATER
if (X25519DiffieHellman.IsSupported)
{
_impl = new BclImpl();
}
else
#endif
{
_impl = new BouncyCastleImpl();
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