Support for TLS System Default Versions included in the .NET Framework 3.5 on Windows 8.1 and Windows Server 2012 R2

Applies to: .NET Framework 3.5 Service Pack 1Windows 8.1Windows Server 2012 R2 Datacenter

The .NET framework version 3.5 SP1 and earlier versions did not provide support for applications to use Transport Layer Security (TLS) System Default Versions as a cryptographic protocol. This update enables the use of TLS v1.2 in the .NET Framework 3.5 SP1.
Note This content has been made available on Windows Update. To obtain the content, scan Windows Update for the latest .NET Framework updates. If your system is fully up to date via Windows Update, you do not need to take further action.


Download information

The following files are available for download from the Microsoft Download Center:

Download Download the x86-based package now.

Download Download the x64-based package now.

We have made the following improvements in this area:

  • The following registry keys can be set to use the operating system defaults for SSL and TLS instead of the hardcoded .NET Framework defaults for a managed application running on the computer.

    • For 64-bit operating systems:

    • For 32-bit operating systems:
    Note If the application has set the ServicePointManager.SecureProtocol in code or through config files to a specific value, or uses the SslStream.AuthenticateAs* APIs to specify a specific SslProtocols enum, the registry setting behavior does not occur.

  • In addition, we have added the SslProtocolsExtensions enumeration that you can use as an option for setting TLS v1.2, TLS v1.1, as well as operating system defaults for the ServicePointManager.SecurityProtocol property when targeting .NET framework version 2.0 SP2. (See the Developer Guidance section for the information on how to use the extensions.)

    Note Windows Vista SP2 and Windows Server 2008 SP2 do not support Transport Layer Security (TLS) protocol versions newer than 1.0. Managed .NET Framework 2.0 SP2 applications running on Windows Vista SP2 or Windows Server 2008 SP2 cannot use TLS 1.2 or TLS 1.1, even if those protocols are set in the ServicePointManager.SecurityProtocol property.

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to obtain Microsoft support files from online services
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Developer Guidance

The definition of the new extensions are in the following files:

  • SecurityProtocolTypeExtensions.cs
    namespace System.Net
    using System.Security.Authentication;
    public static class SecurityProtocolTypeExtensions
    public const SecurityProtocolType Tls12 = (SecurityProtocolType)SslProtocolsExtensions.Tls12;
    public const SecurityProtocolType Tls11 = (SecurityProtocolType)SslProtocolsExtensions.Tls11;
    public const SecurityProtocolType SystemDefault = (SecurityProtocolType)0;
  • SslProtocolsExtensions.cs
    namespace System.Security.Authentication
    public static class SslProtocolsExtensions
    public const SslProtocols Tls12 = (SslProtocols)0x00000C00;
    public const SslProtocols Tls11 = (SslProtocols)0x00000300;
To include the support for TLS v1.2, include the source files in your project and then set the protocol version by using the following methods:

  • Applications that are using ServicePointManager-based APIs can set the protocol using as follows:

    System.Net.ServicePointManager.SecurityProtocol = SecurityProtocolTypeExtensions.Tls12;
  • Applications that are using the SslStream AuthenticateAsClient(String, X509CertificateCollection, SslProtocols, Boolean) overload can set the SslProtocols value as SslProtocolsExtensions.Tls12.
If the registry mentioned in the first paragraph is set and in the application the SslProtocols value is set as SslProtocols.None, then the system default behavior is chosen that will depend on the Windows Operating System version.

Also when you are changing the application code to enable support for TLS v1.2 with .NET Framework 3.5 SP1 you should ensure on computers where this patch is not deployed you handle the following exceptions thrown:

  1. If the hotfix is not installed, ServicePointManager-based APIs (HTTP, FTP, SMTP) will throw "System.NotSupportedException: The requested security protocol is not supported." when the application calls ServicePointManager.SecurityProtocol to set the new value.
  2. If the hotfix is not installed, SslStream-based APIs will throw when calling either of the AuthenticateAs* APIs:
    System.ArgumentException: The specified value is not valid in the 'SslProtocolType' enumeration.
    Parameter name: sslProtocolType
Note For SslStream only, a combination of Tls12, Tls11 with any of the existing Tls, Ssl3, Ssl2 (for example: Tls12 | Tls11 | Tls) will silently downgrade to the existing protocols (for example: Tls) on a system without the patch. It will connect with Tls without throwing the exception.

More Information

To enable TLS v1.1 or v1.2 as operating system defaults, follow the instructions at

Note TLS v1.1 and v1.2 are not available in Windows Vista or Windows Server 2008.

If you have to disable the operating system defaults set by the registry key that is mentioned earlier for specific applications it can be done by adding the following registry key:
<<Full path of the .exe for the file>> DWORD 0
C:\MyApp\MyApp.exe DWORD 0
For more information about TLS v1.2, see Introducing TLS v1.2.

After you enable the SystemDefaultTlsVersions .NET registry key, a different behavior occurs for each version of Windows, as shown in the following table.

Windows versionSSL2 ClientSSL2 ServerSSL3 ClientSSL3 ServerTLS 1.0 ClientTLS 1.0 ServerTLS 1.1 ClientTLS 1.1 ServerTLS 1.2 ClientTLS 1.2 Server
Windows Vista SP2 and Windows Server 2008 SP2OffOnOnOnOnOnN/AN/AN/AN/A
Windows 7 SP1 and Windows Server 2008 R2 SP1OffOnOnOnOnOnOffOffOffOff
Windows Server 2012OffOffOnOnOnOnOnOnOnOn
Windows 8.1 and Windows Server 2012 R2 OffOffOnOnOnOnOnOnOnOn
Windows 10OffOffOnOnOnOnOnOnOnOn
Windows 10 (1511)OffOffOnOnOnOnOnOnOnOn
Windows 10 (1607) and Windows Server 2016N/AN/AOffOffOnOnOnOnOnOn