TLS/SSL Settings

 

Updated: November 5, 2015

Applies To: Windows Vista, Windows Server 2008, Windows 7, Windows 8.1, Windows Server 2008 R2, Windows Server 2012 R2, Windows Server 2012, Windows 8

This reference topic for the IT professional contains registry setting, Group Policy, and network port information for the Windows implementation of the Transport Layer Security (TLS) protocol and the Secure Sockets Layer (SSL) protocol through the Schannel Security Support Provider (SSP).

This topic is divided into the following sections:

The following registry subkeys and entries can help you administer and troubleshoot the Schannel SSP, specifically the TLS and SSL protocols.

System_CAPS_cautionCaution

This information is provided as a reference to use when you are troubleshooting or verifying that the required settings are applied. We recommend that you do not directly edit the registry unless there is no other alternative. Modifications to the registry are not validated by the Registry Editor or by the Windows operating system before they are applied. As a result, incorrect values can be stored, and this can result in unrecoverable errors in the system. When possible, instead of editing the registry directly, use Group Policy or other Windows tools such as the Microsoft Management Console (MMC) to accomplish tasks. If you must edit the registry, use extreme caution.

This entry does not exist in the registry by default. The default value is that all four certificate mapping methods, listed below, are supported.

When a server application requires client authentication, Schannel automatically attempts to map the certificate that is supplied by the client computer to a user account. You can authenticate users who sign in with a client certificate by creating mappings, which relate the certificate information to a Windows user account. After you create and enable a certificate mapping, each time a client presents a client certificate, your server application automatically associates that user with the appropriate Windows user account.

In most cases, a certificate is mapped to a user account in one of two ways:

  • A single certificate is mapped to a single user account (one-to-one mapping).

  • Multiple certificates are mapped to one user account (many-to-one mapping).

By default, the Schannel provider will use the following four certificate mapping methods, listed in order of preference:

  1. Kerberos service-for-user (S4U) certificate mapping

  2. User principal name mapping

  3. One-to-one mapping (also known as subject/issuer mapping)

  4. Many-to-one mapping

Applicable versions: As designated in the Applies To list that is at the beginning of this topic

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

This entry does not exist in the registry by default. For information about ciphers that are used by the Schannel SSP, see Supported Cipher Suites and Protocols in the Schannel SSP.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

To disable a cipher, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. When you disable any algorithm, you disallow all cipher suites that use that algorithm. To enable the cipher, change the DWORD value to 1.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\CipherSuites

To disable a cipher suite, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. When you disable any algorithm, you disallow all cipher suites that use that algorithm. To enable the cipher suite, change the DWORD value to 1.

For information about cipher suites that are used by the Schannel SSP, see Supported Cipher Suites and Protocols in the Schannel SSP.

This entry controls the amount of time that the operating system takes in milliseconds to expire client-side cache entries. A value of 0 turns off secure-connection caching. This entry does not exist in the registry by default.

The first time a client connects to a server through the Schannel SSP, a full TLS/SSL handshake is performed. When this is complete, the master secret, cipher suite, and certificates are stored in the session cache on the respective client and server.

Applicable versions: See the following default client cache time table.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

Default client cache time

Windows Version

Time

Windows Server 2012 R2 and Windows 8.1

10 hours

Windows Server 2012 and Windows 8

10 hours

Windows Server 2008 R2 and Windows 7

10 hours

Windows Server 2008 and Windows Vista

10 hours

This entry controls Federal Information Processing (FIPS) compliance. The default is 0.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\LSA

Windows Server FIPS cipher suites: See Supported Cipher Suites and Protocols in the Schannel SSP.

This subkey controls use of hash algorithms.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

To disable a hash algorithm, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. When you disable any algorithm, you disallow all cipher suites that use that algorithm. To enable the hash algorithm, change the DWORD value to 1.

Hashes subkey table

Subkey

Description

Default

MD5

Controls the use of MD5 as the hashing algorithm.

Enabled

SHA

Controls the use of SHA1, SHA256, and SHA384 as the hashing algorithm.

Enabled

System_CAPS_noteNote

SHA256 and SHA384 were introduced in Windows Server 2008 R2.

For a list of supported cipher suites and hash algorithms, see Supported Cipher Suites and Protocols in the Schannel SSP.

This entry controls the size of the issuer cache, and it is used with issuer mapping. The Schannel SSP attempts to map all of the issuers in the client’s certificate chain—not only the direct issuer of the client certificate. When the issuers do not map to an account, which is the typical case, the server might attempt to map the same issuer name repeatedly, hundreds of times per second.

To prevent this, the server has a negative cache, so if an issuer name does not map to an account, it is added to the cache and the Schannel SSP will not attempt to map the issuer name again until the cache entry expires. This registry entry specifies the cache size. This entry does not exist in the registry by default. The default value is 100.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

This entry controls the length of the cache timeout interval in milliseconds. The Schannel SSP attempts to map all of the issuers in the client’s certificate chain—not only the direct issuer of the client certificate. In the case where the issuers do not map to an account, which is the typical case, the server might attempt to map the same issuer name repeatedly, hundreds of times per second.

To prevent this, the server has a negative cache, so if an issuer name does not map to an account, it is added to the cache and the Schannel SSP will not attempt to map the issuer name again until the cache entry expires. This cache is kept for performance reasons, so that the system does not continue trying to map the same issuers. This entry does not exist in the registry by default. The default value is 10 minutes.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

This subkey controls the use of key exchange algorithms.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

To disable a key exchange algorithm, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. When you disable any algorithm, you disallow all cipher suites that use that algorithm. To enable the key exchange algorithm, change the DWORD value to 1.

Exchange algorithm subkey table

Subkey

Description

Default

Diffie-Hellman\Enabled

Controls the use of Diffie-Hellman (DH) for key exchange.

Enabled

PKCS

Controls the use of RSA for key exchange.

Enabled

This entry controls the maximum number of cache elements. Setting MaximumCacheSize to 0 disables the server-side session cache and prevents reconnection. Increasing MaximumCacheSize above the default values causes Lsass.exe to consume additional memory. Each session-cache element typically requires 2 to 4 KB of memory. This entry does not exist in the registry by default. The default value is 20,000 elements.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

This subkey controls the use of the Private Communications Transport (PCT) protocol.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

To disable the PCT protocol, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. To enable the protocol, change the DWORD value to 1.

PCT subkey table

Subkey

Description

Default

Client

Controls the use of the PCT protocol on the client

Enabled

Server

Controls the use of the PCT protocol on the server

Enabled

DisabledByDefault

Controls disabling the PCT protocol by default. This entry does not exist in the registry by default.

Enabled

This entry controls the flag that is used when the list of trusted issuers is sent. In the case of servers that trust hundreds of certification authorities for client authentication, there are too many issuers for the server to be able to send them all to the client computer when requesting client authentication. In this situation, this registry key can be set, and instead of sending a partial list, the Schannel SSP will not send any list to the client.

Not sending a list of trusted issuers might impact what the client sends when it is asked for a client certificate. For example, when Internet Explorer receives a request for client authentication, it only displays the client certificates that chain up to one of the certification authorities that is sent by the server. If the server did not send a list, Internet Explorer displays all of the client certificates that are installed on the client.

This behavior might be desirable. For example, when PKI environments include cross certificates, the client and server certificates will not have the same root CA; therefore, Internet Explorer cannot chose a certificate that chains up to one of the server’s CAs. By configuring the server to not send a trusted issuer list, Internet Explorer will send all its certificates.

This entry does not exist in the registry by default. This value is True by default.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

This entry controls the amount of time in milliseconds that the operating system takes to expire server-side cache entries. A value of 0 disables the server-side session cache and prevents reconnection. Increasing ServerCacheTime above the default values causes Lsass.exe to consume additional memory. Each session cache element typically requires 2 to 4 KB of memory. This entry does not exist in the registry by default.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL

Default server cache time: 10 hours

This subkey controls the use of SSL 2.0.

SSL 2.0 is disabled by default on Windows client computers.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic excluding Windows client versions.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

To disable the SSL 2.0 protocol, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. To enable the protocol, change the DWORD value to 1.

SSL 2.0 subkey table

Subkey

Description

Default

Client

Controls the use of SSL 2.0 on the client.

Disabled

Server

Controls the use of SSL 2.0 on the server.

Enabled

DisabledByDefault

Flag to disable SSL 2.0 by default.

Enabled

This subkey controls the use of SSL 3.0.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

To disable the SSL 3.0 protocol, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. To enable the protocol, change the DWORD value to 1.

SSL 3.0 subkey table

Subkey

Description

Default

Client

Controls the use of SSL 3.0 on the client.

Enabled

Server

Controls the use of SSL 3.0 on the server.

Enabled

DisabledByDefault

Flag to disable SSL 3.0 by default.

Enabled

This subkey controls the use of TLS 1.0.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

To disable the TLS 1.0 protocol, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. To enable the protocol, change the DWORD value to 1.

TLS 1.0 subkey table

Subkey

Description

Default

Client

Controls the use of TLS 1.0 on the client.

Enabled

Server

Controls the use of TLS 1.0 on the server.

Enabled

DisabledByDefault

Flag to disable TLS 1.0 by default.

Enabled

This subkey controls the use of TLS 1.1.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic excluding those versions prior to Windows Server 2008 R2 and Windows 7.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

To disable the TLS 1.1 protocol, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. To enable the protocol, change the DWORD value to 1.

TLS 1.1 subkey table

Subkey

Description

Default

Client

Controls the use of TLS 1.1 on the client.

Enabled

Server

Controls the use of TLS 1.1 on the server.

Enabled

DisabledByDefault

Flag to disable TLS 1.1 by default.

Enabled

This subkey controls the use of TLS 1.2.

Note: For TLS 1.2 to be enabled and negotiated on servers that run Windows Server 2008 R2, you MUST create the "DisabledByDefault" entry in the appropriate subkey (Client, Server) and set it to "0". The entry will not be seen in the registry and it is set to "1" by default.

Applicable versions: As designated in the Applies To list that is at the beginning of this topic excluding those versions prior to Windows Server 2008 R2 and Windows 7.

Registry path: HKLM SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

To disable the TLS 1.2 protocol, create an Enabled entry in the appropriate subkey. This entry does not exist in the registry by default. After you have created the entry, change the DWORD value to 0. To enable the protocol, change the DWORD value to 1.

TLS 1.2 subkey table

Subkey

Description

Default

Client

Controls the use of TLS 1.2 on the client.

Enabled

Server

Controls the use of TLS 1.2 on the server.

Enabled

DisabledByDefault

Flag to disable TLS 1.2 by default.

Enabled

The following table lists and describes the Group Policy setting that is associated with the Schannel SSP.

Group Policy setting associated with Schannel SSP

Group Policy Setting

Description

System cryptography: Use FIPS-compliant algorithms for encryption, hashing, and signing.

(This is a Security options Group Policy setting.)

Changes to this setting determine whether the Schannel SSP will support the TLS protocol as a client(or as a server, if applicable), and if it will use only the following algorithms:

  • Triple Data Encryption Algorithm (Triple DES) for the TLS traffic encryption

  • Rivest-Shamir-Adleman (RSA) public key algorithm for the TLS key exchange and authentication

  • Secure Hash Algorithm version 1 (SHA-1) for TLS hashing

The client and the server must support these algorithms and TLS to communicate by using a secure channel application. For example, if you enable this policy setting, you also need to configure Internet Explorer to use TLS (which is Off by default) to connect by using Secure Hypertext Transfer Protocol (HTTPS) to a server with this setting.

For more information about this setting, see System cryptography: Use FIPS compliant algorithms for encryption, hashing, and signing.

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