Key Takeaways
- SCEP automates certificate management for managed devices in an MDM. With an API key and a shared secret, users can self-enroll for a certificate without the need for manual intervention.
- A static challenge password can increase your exposure risk. Once a hacker gets the API key, they can manipulate the CA request for a malicious certificate.
- Dynamic SCEP produces a different challenge API key every time a request is made, thus limiting reuse of an intercepted challenge password.
Managing certificates across an organization’s devices can get complicated without automation. The Simple Certificate Enrollment Protocol (SCEP) simplifies the process by automating certificate requests to a certificate authority (CA), helping organizations scale certificate-based authentication and encryption.
Microsoft Intune and Jamf use SCEP to deploy certificates to the endpoints they manage, such as laptops, phones and tablets. Automating certificate management helps reduce misconfigurations, operational overhead and security risks.
However, traditional SCEP has limitations in how certificate enrollment is authorized. Dynamic SCEP builds on the protocol with more flexible, policy-driven certificate issuance based on device identity and authentication requirements.
What Is Dynamic SCEP?
Dynamic SCEP uses a unique challenge password generated for each enrollment request and delivered to the device through an MDM such as Intune or Jamf.
With Microsoft Intune, Intune creates the challenge, encrypts and signs it, and sends it to the device with the SCEP request. When the device sends a certificate enrollment request, the SCEP server sends the CSR and the challenge to Intune, which validates the signature and compares the CSR to the expected values.
With Jamf, a Jamf webhook requests the challenge from SecureW2’s JoinNow CloudConnector, which validates the user in Jamf with a lookup before issuing the dynamic challenge. Upon successful verification, the device can enroll certificates for network access.
The dynamic SCEP challenge password is signed and encrypted by the MDM. When a device sends a certificate enrollment request, the SCEP server sends the CSR and the encrypted password to the MDM for validation. Upon successful verification, the device can enroll certificates for network access.
A dynamic SCEP key consists of the following:
- A dynamically generated password that changes every time a new request is placed.
- Parameters that are expected in the CSR.
- The expiry time of the challenge password.
Traditional SCEP automates certificate enrollment at scale, but using static challenge secrets and pre-shared credentials can introduce security risks. Dynamic SCEP improves security by using unique challenge passwords for certificate requests.
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Dynamic SCEP vs. SCEP: Quick Overview
A dynamic SCEP challenge enhances security by generating a unique challenge key for each request. This prevents the misuse of passwords and ensures that only trusted devices and authorized users can authenticate themselves to a network.
|
Features |
SCEP |
Dynamic SCEP |
|---|---|---|
|
Password |
It uses a static challenge secret for all devices. |
It uses a dynamic challenge password generated by the MDM |
|
Challenge Type |
Static SCEP requires only a pre-shared key for any authentication needs. |
Dynamic SCEP requires an API connection between the SCEP service and the MDM, such as a Microsoft Entra app registration for Intune or Jamf API credentials for Jamf. |
|
Security |
It is less secure as it heightens the chance of unauthorized access |
It is more secure as it does not authorize devices with the wrong password to access the server. |
|
Configuration |
SCEP challenge password provides the pre-shared key upon enrollment. |
Dynamic SCEP must be configured in an MDM. |
Dynamic SCEP and SCEP: The Key Difference in How They Work
SCEP and dynamic SCEP differ in how certificate enrollment is authorized:
- SCEP: Uses a configured challenge password to authorize certificate requests. If the password is shared or improperly managed, unauthorized devices may obtain certificates.
- Dynamic SCEP: Uses dynamically generated challenge passwords validated through the mobile device management (MDM) system, providing more granular control over certificate enrollment.
Dynamic validation reduces the risks associated with reusing the same challenge passwords across devices.
How Dynamic SCEP Works
Dynamic SCEP adds a device-validation step to certificate enrollment by connecting the MDM platform with the SCEP enrollment service.
- MDM enrollment: The device is enrolled in a mobile device management (MDM) platform.
- Dynamic challenge generation: A unique challenge is generated for the device's certificate enrollment request.
- Challenge validation: The enrollment service validates the challenge against the relevant device or enrollment information.
- Certificate issuance: If validation succeeds, the request proceeds through the configured certificate issuance process.
Prefer a visual explanation? Take a look at our video on what is dynamic SCEP and how does it work below:
Key Benefits of Dynamic SCEP
Dynamic SCEP strengthens certificate enrollment by validating device requests instead of relying on a shared challenge password.
- Reduced risk of unauthorized enrollment: Unique, single-use challenges make it harder for attackers to reuse intercepted enrollment credentials to obtain certificates.
- Device-specific validation: Integration with MDM platforms such as Microsoft Intune and Jamf helps verify that a device is enrolled and authorized before a certificate is issued.
- Automated certificate provisioning: Organizations can continue using automated SCEP enrollment while adding validation checks, reducing the need for manual approval of individual requests.
Dynamic SCEP Best Practices for a Network Environment
Reusing the same challenge password can expose a network to unauthorized access. Organizations should follow these best practices when using SCEP:
First, separate certificate authorities by user group. Use a separate intermediate CA for each user group where appropriate. This can help isolate the impact of a compromised intermediate CA and protect the root CA's private key.
Second, monitor enrollment and security events. Implement a security information and event management (SIEM) tool to centralize logs, correlate events and identify suspicious certificate enrollment activity.
Third, consider ACME for Apple devices managed through Jamf. ACME may be an alternative to SCEP for supported certificate enrollment workflows. Verify that the specific device and MDM configuration supports the intended method before switching protocols.
Lastly, use dynamic SCEP where supported. Configure dynamic challenge validation in the enrollment profile to reduce reliance on static, shared challenge passwords.
What Is SCEP?
Traditional Simple Certificate Enrollment Protocol (SCEP) automates certificate issuance across networked devices, enabling scalable authentication and encryption. Instead of relying on manual provisioning, SCEP allows devices to request certificates directly from a CA.
In certificate-based network access environments, devices without valid certificates can be denied access, helping organizations restrict connectivity to authorized devices.
However, traditional SCEP can introduce security risks when enrollment relies on static, shared challenge passwords or insufficient request validation. If these secrets are exposed or reused, unauthorized devices may obtain certificates.
Dynamic SCEP addresses this limitation by introducing more flexible challenge-based validation for certificate enrollment.
Watch the introductory video below on SCEP to understand it better:
How SCEP Certificate Enrollment Works
SCEP automates certificate enrollment by allowing devices to request certificates from a CA. The process typically involves these steps:
- CA certificate retrieval: The device obtains the CA certificate to establish trust in the certificate issuer.
- Key pair generation: The device generates a public-private key pair and creates a certificate signing request (CSR) containing its public key and requested certificate information.
- Certificate request submission: The device sends the CSR to the SCEP server, along with the required enrollment authorization information, such as a challenge password when configured.
- Request validation and approval: The CA validates the request and its authorization according to its policies. Requests may be approved automatically or held for manual approval.
- Certificate issuance: If the request is approved, the CA issues the certificate and returns it to the device for installation.
Once installed, the certificate can be used for certificate-based authentication protocols such as EAP-TLS, enabling network infrastructure to authenticate devices before granting access.
Primary Advantages of SCEP
SCEP simplifies certificate management by automating enrollment across large device fleets. Its primary advantages include:
- Automated certificate enrollment: Devices can request certificates without requiring administrators to provision each certificate manually.
- Scalable device authentication: Organizations can deploy certificates across devices, helping support certificate-based authentication for Wi-Fi, VPNs, and other network resources.
- Broad MDM support: SCEP integrates with device management platforms such as Microsoft Intune and Jamf to automate certificate deployment to managed devices.
- Reduced administrative overhead: Automated enrollment and deployment reduce repetitive IT tasks associated with issuing certificates at scale.
- Support for secure communications: Issued certificates enable encryption and authentication when used with compatible security protocols and properly configured systems.
Despite these advantages, traditional SCEP has limitations in how certificate enrollment is authorized, which can introduce security risks if challenge passwords are not properly managed.
SCEP Implementation Best Practices
A secure SCEP deployment requires careful configuration of certificate enrollment, CA policies and device management.
|
Best Practice
|
Description |
|---|---|
|
Protect Challenge Passwords
|
Avoid shared, static challenge passwords where possible. If required, restrict access, rotate them regularly and avoid exposing them in device profiles or logs.
|
|
Validate Certificate Requests
|
Configure the CA to verify enrollment requests and enforce approval policies that meet the organization's security requirements.
|
|
Secure the SCEP Endpoint
|
Use HTTPS where supported and properly configured to protect enrollment communications in transit.
|
|
Define Certificate Profiles
|
Restrict certificate templates, key usage, validity periods and subject attributes to the intended device identities and purposes.
|
|
Manage Certificate Lifecycles
|
Establish procedures for certificate renewal, expiration monitoring and prompt revocation when devices are compromised, retired or no longer authorized.
|
|
Monitor Enrollment Activity
|
Log and review certificate requests, failed authorization attempts and unusual issuance patterns to identify potential misuse.
|
|
Test Before Deployment
|
Validate enrollment, renewal, revocation and failure scenarios in a test environment before rolling out SCEP across the organization.
|
Do SCEP Deployments Leave Your Network Unsafe?
SCEP automates the distribution of certificates to end users in an organizational network, but it does not authenticate or identify the user. If a user has an SCEP challenge password, they can submit a request for a certificate using the same password generated for the organization.
This SCEP model, with a single URL, would work effectively in an admin-only mode.
However, SCEP challenge passwords become a concern when used by end users and devices outside the trusted network, such as with MDMs and BYOD scenarios. The illustration below shows how attackers intercept SCEP certificate requests.
This would allow the user or device to take the SCEP challenge password and get a certificate for a different user level with higher network access or a different CA certificate than the intended one. It would also allow an attacker to pose as a legitimate user and use the challenge password to orchestrate attacks on the network.
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Dynamic SCEP With SecureW2 for a More Secure Network
An organization must have a scalable and usable certificate distribution system to successfully deploy certificate-based authentication in a network environment. The SecureW2 Managed Device Gateway API uses dynamic SCEP to deploy certificate-based authentication with EAP-TLS in a WPA2-Enterprise network environment for secure, passwordless authentication.
SecureW2 is listed by Microsoft as a third-party certification authority partner for Intune. Admins create a device management platform in the JoinNow Management Portal, which provides the Endpoint URI for the SCEP certificate profile in Intune.
An identity provider supplies the endpoint URL to be added to the SCEP profile in Intune. The CA is used here to configure the SCEP process.
SecureW2 automatically revokes certificates when a device is removed from Intune or added to a designated Jamf revocation group, minimizing the admin’s effort to revoke certificates manually.
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Frequently Asked Questions
What is the difference between SCEP and PKCS certificates?
SCEP and PKCS differ in how certificate enrollment is handled. SCEP automates certificate requests and issuance between devices and a certificate authority (CA), while PKCS is a family of standards for packaging, exchanging and managing cryptographic keys and certificates. PKCS#10 defines certificate requests, while PKCS#12 packages certificates and private keys.
What is dynamic SCEP used for?
Dynamic SCEP is used to automate certificate enrollment with unique, time-limited challenge passwords or enrollment credentials. It helps organizations securely issue certificates to devices at scale while reducing the risks associated with static, shared SCEP passwords.
What does a SCEP server do?
A SCEP server handles certificate enrollment requests from devices and facilitates communication with a certificate authority (CA). It processes enrollment requests, supports device authentication through challenge passwords, and helps deliver issued certificates, enabling automated certificate provisioning across large device fleets.
What is the primary difference between SCEP and dynamic SCEP?
Traditional SCEP often uses static, shared challenge passwords for certificate enrollment, which can create security risks if exposed or reused. Dynamic SCEP uses unique, temporary challenge passwords to improve enrollment security and reduce the risk of unauthorized certificate issuance.
