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Friday, March 23 2018 @ 07:24 AM EDT

How to disable PCT 1.0, SSL 2.0, SSL 3.0, or TLS 1.0 in Internet Information Services

You can use HTTPS to connect to either of the following:

  • Microsoft Internet Information Server (IIS) versions 3.0 and later versions
  • Microsoft Internet Information Services (IIS) 5.0 and later versions

When you do this, the client and the server negotiate a common protocol to help secure the channel. If the server and the client have multiple protocols in common, IIS tries to help secure the channel with one of the protocols that IIS supports. The protocol that IIS uses is selected in the following order of preference:

  1. PCT 1.0
  2. SSL 3.0
  3. SSL 2.0

Sometimes, you may want to disable one or more of these protocols. You can do this if you change the registry.

Microsoft Windows NT Server stores information about different security-enhanced channel protocols that Windows NT Server supports. This information is stored in the following registry key:

HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols

Typically, this key contains the following subkeys:

  • PCT 1.0
  • SSL 2.0
  • SSL 3.0
  • TLS 1.0

Each key holds information about the protocol for the key. Any one of these protocols can be disabled at the server. To do this, you create a new DWORD value in the server subkey of the protocol. You set the DWORD value to "00 00 00 00."

Note By default, PCT is not enabled on Microsoft Windows Server 2003.

To disable the PCT 1.0 protocol so that IIS does not try to negotiate using the PCT 1.0 protocol, follow these steps:

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

322756  ( ) How to back up and restore the registry in Windows.

For information about how to modify the registry, see the "Changing keys and values" Help topic in Registry Editor. Also see the "Add and delete information in the registry" Help topic and the "Edit registry data" Help topic in Registry Editor.
  1. Click Start, click Run, type regedt32 or type regedit, and then click OK.
  2. In Registry Editor, locate the following registry key:

    HKey_Local_Machine\System\CurrentControlSet\Control\SecurityProviders \SCHANNEL\Protocols\PCT 1.0\Server
  3. On the Edit menu, click Add Value.
  4. In the Data Type list, click DWORD.
  5. In the Value Name box, type Enabled, and then click OK.

    Note If this value is present, double-click the value to edit its current value.
  6. Type 00000000 in Binary Editor to set the value of the new key equal to "0".
  7. Click OK. Restart the computer.

This information comes from KB Article 187498.

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