Domain-joined Device Public Key Authentication
Applies to: Windows Server 2022, Windows Server 2019, Windows Server 2016, Windows 10
Kerberos added support for domain-joined devices to sign-in using a certificate beginning with Windows Server 2012 and Windows 8. This change allows 3rd party vendors to create solutions to provision and initialize certificates for domain-joined devices to use for domain authentication.
Automatic public key provisioning
Beginning with Windows 10 version 1507 and Windows Server 2016, domain-joined devices automatically provision a bound public key to a Windows Server 2016 domain controller (DC). Once a key is provisioned, then Windows can use public key authentication to the domain.
If the device is running Credential Guard, then a public/private key pair is created protected by Credential Guard.
If Credential Guard is not available and a TPM is, then a public/private key pair is created protected by the TPM.
If neither is available, then a key pair is not generated and the device can only authenticate using password.
Provisioning computer account public key
When Windows starts up, it checks if a public key is provisioned for its computer account. If not, then it generates a bound public key and configures it for its account in AD using a Windows Server 2016 or higher DC. If all the DCs are down-level, then no key is provisioned.
Configuring device to only use public key
If the Group Policy setting Support for device authentication using certificate is set to Force, then the device needs to find a DC that runs Windows Server 2016 or later to authenticate. The setting is under Administrative Templates > System > Kerberos.
Configuring device to only use password
If the Group Policy setting Support for device authentication using certificate is disabled, then password is always used. The setting is under Administrative Templates > System > Kerberos.
Domain-joined device authentication using public key
When Windows has a certificate for the domain-joined device, Kerberos first authenticates using the certificate and on failure retries with password. This allows the device to authenticate to down-level DCs.
Since the automatically provisioned public keys have a self-signed certificate, certificate validation fails on domain controllers that do not support Key Trust account mapping. By default, Windows retries authentication using the device's domain password.
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