How Does a Web Server Use Negotiate & NTLM?


Angela Bailey

How Does a Web Server Use Negotiate & NTLM?

When it comes to web server authentication, Negotiate and NTLM are two commonly used protocols. This article will explore how web servers use these protocols to authenticate users and ensure secure communication. Let’s dive in!

The Basics of Negotiate and NTLM

Before we delve into the details, let’s briefly understand what Negotiate and NTLM are:

  • Negotiate: Negotiate is an authentication protocol that allows the client and server to negotiate the most secure authentication method they both support. It supports various authentication mechanisms, including Kerberos and NTLM.
  • NTLM: NTLM (NT LAN Manager) is a suite of security protocols developed by Microsoft for authenticating users in a Windows network environment.

The Authentication Process

When a user accesses a web server that uses Negotiate or NTLM, the following steps occur:

  1. Request from the Client: The client sends an HTTP request to the server, indicating its willingness to use either Negotiate or NTLM for authentication.
  2. Negotiation Phase: The server responds with an HTTP 401 Unauthorized status code along with a challenge. This challenge specifies which authentication schemes are supported by the server.
  3. Response from the Client: The client chooses either Negotiate or NTLM based on its capabilities and sends another request to the server, including its credentials encrypted with either of these protocols.
  4. Authentication Verification: The server validates the credentials by decrypting them using either Negotiate or NTLM. If the credentials are valid, the server grants access to the requested resource; otherwise, it returns an HTTP 401 status code.

Key Differences Between Negotiate and NTLM

While both Negotiate and NTLM serve the purpose of user authentication, they have some key differences:

  • Security: Negotiate is considered more secure than NTLM as it supports Kerberos, which is a stronger authentication mechanism. NTLM uses various hashing algorithms but is generally more susceptible to attacks.
  • Compatibility: Negotiate is backward compatible with NTLM, meaning it can fall back to using NTLM if the client or server doesn’t support Kerberos authentication. NTLM, on the other hand, does not support Negotiate.
  • Performance: Negotiate requires an additional round-trip between the client and server during the negotiation phase, which can slightly impact performance compared to NTLM.

Incorporating Negotiate and NTLM in Web Servers

To use Negotiate or NTLM in a web server environment, certain configurations need to be made. Here’s a high-level overview of how these protocols can be incorporated:

Negotiate Configuration:

  1. Kerberos Setup: Ensure that the web server and client machines are part of a Windows domain where Kerberos authentication can be performed.
  2. Negotiate Module Installation: Install and configure the necessary modules or extensions on your web server that support Negotiate authentication (e.g., mod_auth_kerb for Apache).
  3. Configuration Changes: Modify your web server’s configuration files to enable Negotiate authentication and specify any additional settings required.

NTLM Configuration:

  1. Windows Authentication: Enable Windows Authentication on your web server.
  2. NTLM Provider Setup: Configure the web server to use the NTLM provider for authentication.
  3. Security Considerations: Ensure that proper security measures are in place to protect against NTLM-related vulnerabilities, such as enforcing strong password policies and regularly updating server software.


Negotiate and NTLM are essential protocols used by web servers for user authentication. While Negotiate offers better security with its support for Kerberos, NTLM remains widely used due to its compatibility in Windows environments. By understanding how these protocols work and incorporating them correctly, you can ensure secure access to your web applications or resources.

Remember, choosing the right authentication protocol depends on your specific requirements and the level of security you need. Stay informed about the latest developments in web server authentication to keep your systems safeguarded!

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