Microsoft CNG

CNG handles cryptographic primitives and key storage through separate APIs. In both cases a Windows application contacts a router, which forwards the cryptographic operation to the provider that is configured to handle the request. For an illustration of communication between the architecture layers for cryptographic primitives, see the following diagram.

For an illustration of communication between the architecture layers for cryptographic key storage, see the following diagram.

This section lists the National Security Agency (NSA) classified Suite B algorithms supported by the nShield CNG providers.

When an application needs keys that are protected by an Operator Card Set or a Softcard, a user interface is invoked to prompt the application user to insert the smart card and/or enter appropriate passphrases.

There can only be one instance of the agent running (indicated by a blue globe in the Tray Notification area in the toolbar). Attempts to start a second instance will fail with a CreateNamedPipe error. If the agent is not running, attempts to invoke dialogs through it will fail and this is logged in the Windows Event Log. It can be restarted by logging off and on or by explicitly executing either %NFAST_HOME%\bin\nShield_service_agent64.exe or %NFAST_HOME%\bin\nShield_service_agent.exe. On 64 bit platforms either of these can be used irrespective of the bit size of the underlying application.

For more information about auto-loadable card sets and the considerations of silent mode, see the authorisation requests diagram towards the end of this section.

You define key protection and authorization settings with the CNG Configuration Wizard on the Key Protection Setup screen. For more information about the CNG Configuration Wizard, see the User Guide for your HSM.

The options on this screen that are relevant to key protection and authorization are:

If you select Softcard or Operator Card Set protection, you will be offered the choice between selecting an existing protection token and creating a new one on the next page.

The CNG Configuration Wizard can be re-run to change the default protection. Existing keys that were generated with a different protection can still be loaded even if they don’t match the protection that was selected in the wizard.

The key storage providers always respect calls made with the Silent option. Primitive providers never display a user interface.

Applications may have a mechanism to disable silent mode operation, thereby allowing appropriate passphrases to be entered. Ensure that you configure applications to use an appropriate level of key protection. For example, in Microsoft Certificate Services, you must select the Use strong private key protection features provided by the CSP option to disable silent mode operation.

You can configure the CNG provider to count the number of times a key is used. Use this functionality, for example, to retire a key after a set number of uses, or for auditing purposes.

To enable key use counting in the Security World Key Storage Provider, call NCryptSetProperty with NCRYPT_USE_COUNT_ENABLED_PROPERTY on the provider handle. Alternatively, to override the behavior of third-party software that would not otherwise provide the user with the option to enable key use counting, use one of the following methods:

Keys created while the provider has key use counting enabled continue to have their use counts incremented, regardless of the state of the provider’s handle. Key use counts are not recorded for keys created while the NCRYPT_USE_COUNT_ENABLED_PROPERTY is disabled on the provider handle.

Because the key counter is a 64-bit area in a specific module’s NVRAM, the counted keys are specific to a single module. When a key is created you are prompted to specify which module to use, unless there is only one module in the Security World, or preload was used to preload authorization from an ACS on only one module.

The key counter is incremented each time a private key is used to:

To test the performance of keys with counters, run the cngsoak command with the -C option:

To view the current key use count for keys, run the cnglist command with the --list-keys and --verbose options:

We now provide the capability to use keys generated by CAPI in CNG applications. This is provided through the standard NCryptOpenKey CNG API call. Passing either AT_SIGNATURE or AT_KEYEXCHANGE as the dwLegacyKeySpec parameter and the CAPI container name as the pszKeyName parameter will invoke this mode of operation. The CAPI key will be loaded into the CNG provider and will behave as if it was a CNG key. Any key authorization required will be handled with a user interface being invoked to prompt the application user to insert the smart card or enter appropriate passphrases. There is support for Key Usage and Key Counting properties.

The CNG application has to be written such that it calls NCryptOpenKey to open a CAPI key explicitly.

Use the nfkmverify command-line utility to check the security of all stored keys in the Security World. Use nfkminfo, nfkmcheck, and other command-line utilities to assist in this process. For more information about these command-line utilities, see the User Guide for your HSM.

The following table lists the utilities specific to the nShield CNG CSP:

For more information about the command-line utilities, see the User Guide for your HSM.

A set of environment variables are supported for controlling CNG protection options on a per-application basis. These variables are documented here to facilitate more complicated deployments, but it should be noted that they are liable to change between releases.