A single weak hash algorithm hiding inside Kerberos certificate authentication can quietly undo years of identity hardening.
Kerberos supports certificate based authentication through PKINIT, the mechanism behind smart cards and Windows Hello for Business certificate trust. Behind the scenes, cryptographic hash algorithms bind the certificate to the authentication ticket, and not all of those algorithms are equally trustworthy.
Attackers who understand legacy cryptography know that outdated hash algorithms such as MD5 or SHA1 can be exploited to forge, collide, or manipulate authentication data, turning a passwordless authentication method into an unexpected attack surface.
The PKInitHashAlgorithmConfiguration setting lets Windows restrict which hash algorithms the Kerberos client is permitted to use during certificate based logon, explicitly rejecting weaker algorithms in favor of modern, strong ones.
Enforcing this through Microsoft Intune matters because it removes guesswork and manual registry edits from the equation, applying the same cryptographic baseline to every managed endpoint regardless of who provisioned the device.
The result is an environment where Kerberos certificate authentication only trusts cryptography strong enough to resist forgery attempts.
Why This Policy Matters
Kerberos remains the backbone authentication protocol in Active Directory and hybrid environments, and certificate based authentication is expanding rapidly through passwordless initiatives. Attackers know that authentication protocols are only as strong as their weakest accepted algorithm.
Without explicit restriction, Windows may continue to accept legacy hash algorithms for backward compatibility, leaving a quiet gap for downgrade or collision based attacks against PKINIT.
Without this policy:
- Legacy hash algorithms like MD5 or SHA1 remain accepted, enabling collision based certificate forgery attempts.
- Attackers can attempt to downgrade PKINIT negotiation to a weaker algorithm without detection.
- Smart card and Windows Hello for Business deployments may rely on inconsistent hash strength across the fleet.
- Without centralized enforcement, configuration drift and untracked exceptions accumulate silently.
With this setting enforced through Intune:
- Certificate based Kerberos authentication only accepts modern, strong hash algorithms.
- Downgrade attempts to weaker algorithms are rejected at the client before authentication completes.
- Every managed device applies the same hash algorithm policy, with no manual configuration required.
- The attack surface for credential theft techniques targeting Kerberos certificate authentication is measurably reduced.
This configuration aligns with modern security principles such as defense in depth, endpoint hardening, proactive threat detection, and Zero Trust architecture.
Security Governance
Security governance ensures that hardening controls are consistently applied, monitored, and aligned with organizational standards.
Without centralized governance, settings such as this one can drift across devices, leaving blind spots that attackers can exploit.
Managing the Configure hash algorithms for certificate logon setting through Microsoft Intune brings several governance benefits:
- Centralized enforcement of the control across all managed Windows endpoints
- Consistent configuration aligned with corporate security baselines
- Clear visibility into deployment status and configuration compliance
- Defined ownership and accountability through scope tags and role-based administration
- An auditable policy lifecycle from creation to enforcement and validation
This level of governance ensures that the control is handled in a controlled and transparent manner, reinforcing compliance with internal security policies and regulatory frameworks.
Windows CSP Overview
This section explains how the setting is exposed at the operating system level and how Microsoft Intune interacts with it. The configuration is powered by the Windows Policy Configuration Service Provider (CSP) framework, specifically the Kerberos area.
| Scope | Editions | Applicable OS |
|---|---|---|
| ✅ Device ❌ User | ✅ Pro ✅ Enterprise ✅ Education ✅ IoT Enterprise / IoT Enterprise LTSC | ✅ Windows 11, version 22H2 [10.0.22621] and later |
This policy setting controls hash or checksum algorithms used by the Kerberos client when performing certificate authentication; if enabled, algorithm states can be configured, and if disabled or not configured, each algorithm assumes the Default state.
Description Framework Properties
This section defines how the configuration behaves at a technical level within the CSP framework.
| Property name | Property value |
|---|---|
| Format | int |
| Access Type | Add, Delete, Get, Replace |
| Default Value | 0 |
Allowed Values
This section defines the valid configuration values supported by the setting. It accepts the following options:
| Value | Description |
|---|---|
| 0 (Default) (Default) | Disabled / Not Configured. |
| 1 | Enabled. |
Group Policy Mapping
For organizations operating in hybrid environments, this CSP setting maps to a corresponding Group Policy configuration.
| Name | Value |
|---|---|
| Name | PKInitHashAlgorithmConfiguration |
| Friendly Name | Configure hash algorithms for certificate logon |
| Location | Computer Configuration |
| Path | System > Kerberos |
| Registry Key Name | Software\Microsoft\Windows\CurrentVersion\Policies\System\Kerberos\Parameters |
| ADMX File Name | Kerberos.admx |
Security Considerations
Before enabling this policy, administrators should understand how it behaves and plan for its impact.
- Confirm the certificate authority templates issue certificates signed with SHA-256 or stronger before restricting weaker algorithms, since existing certificates may otherwise fail authentication.
- Test thoroughly with smart card and Windows Hello for Business certificate trust deployments, since a hash mismatch can cause unexpected logon failures at scale.
- This setting applies only to Windows 11, version 22H2 and later, so mixed fleets with older builds need supplemental compensating controls.
- Coordinate the rollout window with helpdesk and identity teams, since abrupt enforcement can lock out users relying on legacy certificates.
A phased, pilot-first deployment is recommended to validate the behavior in a controlled group and avoid unexpected impact before rolling the setting out across production devices.
How to Configure hash algorithms for certificate logon Using Intune (Settings Catalog)
You can enforce this policy centrally using the Intune Settings Catalog, ensuring that only approved, cryptographically strong hash algorithms are used during Kerberos certificate authentication is applied consistently across all managed Windows devices.
To begin, sign in to the Microsoft Intune admin center and follow the steps below, as illustrated in the screenshots.
Create the Configuration Profile
In the Microsoft Intune admin center:
- Navigate to Devices › Windows › Configuration
- Select + Create policy
In the Create a profile pane:
- Platform: Windows 10 and later
- Profile type: Settings catalog
Click Create to continue.
At this stage, you have created the foundation of a Settings Catalog policy. In the next steps, you will search for and configure the setting that restricts Kerberos PKINIT certificate authentication to approved hash algorithms.
Define Basic Profile Details
After clicking Create, the next step is to define the basic details of the configuration profile. This stage is essential for long-term management, clarity, and governance within Microsoft Intune, especially in environments with multiple endpoint hardening policies and security baselines.
Providing a clear Name and a concise but meaningful Description ensures that the purpose of the policy is immediately understood by administrators and security teams in the future. As shown in the screenshot, configure the fields as follows.
The Platform field is already pre-selected as Windows, so no changes are required. Once the name and description are defined, click Next to proceed to the configuration settings.
Configure the Setting Using the Settings Picker
With the profile basics defined, the next step is to configure the policy using the Settings picker, where you select the exact Windows setting you want to enforce. To open the Settings picker panel, click Add settings.
By default, this setting is not configured, meaning the Kerberos client accepts the operating system default set of hash algorithms without any enforced restriction.
In the search field at the top of the Settings picker, type Configure hash algorithms for certificate logon, and then click Search to filter the results.
From the returned results, select the category Kerberos, and then choose the setting Configure hash algorithms for certificate logon. Once selected, the setting is automatically added to the configuration profile. Back on the configuration page, change the value from its default state to Enabled.
When enabled, Windows restricts PKINIT certificate binding to the approved, cryptographically strong hash algorithms and rejects deprecated ones such as MD5 or SHA1. This ensures that:
- Only approved cryptographic algorithms are used for PKINIT certificate binding.
- Downgrade attempts to deprecated hash algorithms are visible and blocked at the client.
- Authentication tickets carry stronger cryptographic assurance, resistant to collision based forgery.
This configuration aligns with modern endpoint hardening practices and supports Zero Trust security principles.
Configure Scope Tags (Optional)
Scope tags are used to control who can view and manage this policy within the Microsoft Intune admin center. They are particularly useful in environments with delegated administration, multiple IT teams, or regional management models.
As shown in the screenshot, the Default scope tag is selected. This is the standard and recommended configuration for most environments, as it ensures the policy is visible to all administrators who have access to Intune.
Optionally, custom scope tags can be assigned if you need to:
- Restrict policy visibility to specific IT roles or teams
- Enforce administrative separation of duties
- Support delegated or region-based Intune management
If no additional scope tags are required, keep the Default selection and click Next to continue.
Assignments – Kerberos Certificate Hash Algorithm Enforcement
After configuring the policy settings, the next step is to assign the policy to the appropriate target group. Assignments define which devices will receive and enforce this configuration, ensuring the policy is applied in a controlled and intentional manner.
In the Assignments tab, click Add groups under Included groups and search for the group you want to target. This approach allows you to deploy the policy gradually, starting with test devices before expanding to production.
As shown in the screenshot, the policy is assigned to the following group: GRP – MS365Education – Test Computers.
Once the group is selected, verify the following:
- The group appears under Included groups
- The group status is Active
- No assignment filters are applied (unless explicitly required)
At this stage, no Excluded groups are configured, which is appropriate for controlled test deployments.
After confirming the assignment, click Next to proceed to the Review + Create step.
Review + Create – Final Validation
The Review + Create step is the final checkpoint before deploying the policy. This is where you validate that all configurations are correct and aligned with your intended endpoint hardening objective.
Pay special attention to the following items:
- Policy name and description: confirm that the policy clearly reflects its purpose, restricting Kerberos certificate authentication to strong hash algorithms
- Configuration settings: verify that Configure hash algorithms for certificate logon is set to Enabled, under Kerberos
- Scope tags: ensure the correct scope tag is assigned. In this example, the Default scope tag is used
- Assignments: confirm the policy is assigned to the intended group, GRP – MS365Education – Test Computers, and that no unintended exclusions are configured
Once everything has been validated, click Create to finalize and deploy the policy to the assigned devices.
Monitor Policy Deployment Status
After creating and assigning the WIN – Endpoint Hardening – Kerberos Certificate Hash Algorithms configuration profile, the next step is to verify its deployment status. This validation confirms that the policy has been successfully applied and that Kerberos certificate authentication only accepts approved hash algorithms on the targeted devices.
Although Microsoft Intune can take up to 8 hours to automatically deliver configuration profiles, deployment often occurs much faster. If needed, you can accelerate the process by:
- Triggering a manual device sync from the Company Portal
- Initiating a sync directly from the Microsoft Intune admin center
Intune provides clear indicators to evaluate the policy deployment status: Succeeded (devices have applied the policy), In progress (devices are still processing), Error (the policy failed and requires investigation), and Not applicable (the device does not support the configuration).
When devices report Succeeded, it confirms that the hash algorithm restriction is active, ensuring that certificate based Kerberos authentication on that device is hardened against weak-hash exploitation.
Client-Side Verification via Event Viewer
After the device has synced with Intune, you can perform a client-side verification to confirm that the policy was successfully applied. Windows records Intune policy processing events locally, allowing administrators to confirm policy enforcement without relying only on the Intune portal.
- Open Event Viewer on the target device
- Navigate to Applications and Services Logs › Microsoft › Windows › DeviceManagement-Enterprise-Diagnostics-Provider › Admin
- Select Filter Current Log
- Look for Event ID 813 or Event ID 814, which indicate successful processing of Intune configuration policies
- Open the event details and confirm that the Kerberos setting was applied
For deeper validation, you can confirm the effective setting directly on the device. Check the registry path HKLM\SYSTEM\CurrentControlSet\Control\Lsa\Kerberos\Parameters for the value PKInitHashAlgorithmConfiguration = 1, or open the Local Group Policy Editor and navigate to Computer Configuration > Administrative Templates > System > Kerberos to confirm the setting shows as Enabled.
Keep in mind that this setting only affects Kerberos PKINIT certificate authentication flows; it has no impact on password based Kerberos authentication or NTLM fallback scenarios.
Why This Matters for Endpoint Security
Kerberos remains the primary authentication protocol across Active Directory and hybrid environments, and certificate based authentication is expanding rapidly through passwordless initiatives like Windows Hello for Business and smart cards.
Without explicit hash algorithm restrictions, legacy cryptographic weaknesses can be silently exploited to forge or manipulate authentication data, undermining the trust model that Kerberos and the underlying PKI depend on.
By enforcing Configure hash algorithms for certificate logon through Microsoft Intune and validating the configuration locally, organizations ensure that:
- Certificate based authentication only trusts modern, collision resistant cryptography.
- Legacy hash algorithms cannot be leveraged for ticket forgery or manipulation.
- Authentication infrastructure aligns with Zero Trust principles of strong identity assurance.
- Enforcement is consistent across the device fleet, removing forgotten legacy configurations.
This configuration provides strong security value without disrupting standard user workflows when properly validated and deployed.
Key Takeaway
Strong authentication is only as strong as the weakest cryptographic algorithm it is still willing to accept.
Enforcing PKInitHashAlgorithmConfiguration through Microsoft Intune ensures every managed device rejects weak Kerberos certificate hash algorithms without manual intervention or configuration drift.
Combined with centralized deployment and client-side validation, organizations gain measurable, auditable proof that certificate based Kerberos authentication meets modern cryptographic standards.
And in modern security architecture, restricting weak cryptography in Kerberos authentication is not optional, it is essential.
More Information
For additional technical details, refer to the official Microsoft documentation below:
- https://learn.microsoft.com/en-us/windows/client-management/mdm/policy-csp-kerberos#pkinithashalgorithmconfiguration
- https://learn.microsoft.com/en-us/mem/intune/configuration/settings-catalog
- https://learn.microsoft.com/en-us/mem/intune/configuration/device-profiles
- https://learn.microsoft.com/en-us/mem/intune/configuration/device-profile-monitor
- https://learn.microsoft.com/en-us/mem/intune/configuration/device-profile-troubleshoot
Thank you for reading!
🖥️ Ricardo Barbosa
🏆️ Microsoft MVP | 📘 Microsoft Certified Trainer (MCT)
☁️ Intune & Cloud Architect | 💼 Technology Director at Altelix.com
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