> For the complete documentation index, see [llms.txt](https://help.security.gallagher.com/knowledge-hub/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.security.gallagher.com/knowledge-hub/deployment-resources/security-and-compliance/authentication-protocols.md).

# Authentication Protocols

Kerberos and RC4 use in Command Centre.

### Overview

An **authentication protocol** is a system that verifies the identity of a user or computer before granting access to a network or service.

### Terminology

**NT LAN Manager (NTLM)** is a legacy Microsoft Windows single sign-on authentication protocol suite that uses a challenge-response mechanism

**Kerberos** is a computer network authentication protocol that allows users and services to prove their identities to each other securely

**RC4 (Rivest Cipher 4)** is a fast, simple stream cipher designed by Ron Rivest in 1987 that encrypts data one byte at a time

### Detail

* **NTLM is not used.** Gallagher explicitly uses **Kerberos**.
* **RC4** is used to:
  1. Validate passwords set in earlier Command Centre versions. RC4 is unused after a password change.
  2. Decrypt factory keys from the licence file. These keys establish hardware authenticity for **pre-7.80 controllers**.

Command Centre attempts to decrypt factory keys at startup, whether needed or not. It fails to start if the keys cannot be decrypted. RC4 remains required to *start*, not to run, Command Centre. Its removal is not planned.


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