Information
This policy setting determines whether the Transport Layer Security/Secure Sockets Layer (TLS/SSL) Security Provider supports only the TLS_RSA_WITH_3DES_EDE_CBC_SHA cipher suite. Although this policy setting increases security, most public Web sites that are secured with TLS or SSL do not support these algorithms. Client computers that have this policy setting enabled will also be unable to connect to Terminal Services on servers that are not configured to use the FIPS compliant algorithms. Note If you enable this policy setting, computer performance will be slower because the 3DES process is performed on each block of data in the file three times. This policy setting should only be enabled if your organization is required to be FIPS compliant. Important: This setting is recorded in different registry locations depending upon the version of Windows being used. For Windows XP and Windows Server 2003 it is stored at HKLM\System\CurrentControlSet\Control\Lsa\FIPSAlgorithmPolicy, with Windows Vista and later versions of Windows it is stored at HKLM\System\CurrentControlSet\Control\Lsa\FIPSAlgorithmPolicy\Enabled. This means that you must use Windows XP or Windows Server 2003 to edit group policies and security templates which will be applied to computers running Windows XP or Windows Server 2003. However, when editing group policies or security templates which will be applied to computers running Windows Vista or Windows Server 2008 you must use Windows Vista or Windows Server 2008. You can enable this policy setting to ensure that the computer will use the most powerful algorithms that are available for digital encryption, hashing and signing. Use of these algorithms will minimize the risk of compromise of digitally encrypted or signed data by an unauthorized user.
Solution
To implement the recommended configuration state, set the following Group Policy setting to 0.
Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options\System cryptography- Use FIPS compliant algorithms for encryption, hashing, and signing
Impact- Client computers that have this policy setting enabled will be unable to communicate by means of digitally encrypted or signed protocols with servers that do not support these algorithms. Network clients that do not support these algorithms will not be able to use servers that require them for network communications. For example, many Apache-based Web servers are not configured to support TLS. If you enable this setting, you also need to configure Internet Explorer to use TLS. This policy setting also affects the encryption level that is used for the Remote Desktop Protocol (RDP). The Remote Desktop Connection tool uses the RDP protocol to communicate with servers that run Terminal Services and client computers that are configured for remote control; RDP connections will fail if both computers are not configured to use the same encryption algorithms. To enable Internet Explore to use TLS 1. On the Internet Explorer Tools menu, click Internet Options. 2. Click the Advanced tab. 3. Select the Use TLS 1.0 check box. It is also possible to configure this policy setting through Group Policy or by using the Internet Explorer Administrators Kit. Client computers running Windows XP, Windows XP SP1 and Windows XP SP2 that try to connect to a Terminal Services server that has this setting enabled will be unable to communicate with the server until an updated version of the Terminal Services client is installed. This issue could aslo affect Remote Assistance and Remote Desktop connections. For more information about the issue and how to resolve it see 'Remote Assistance connection to Windows Server 2003 with FIPS encryption does not work' at http-//support.microsoft.com/default.aspx?scid=kb;en-us;811770.