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CISSP · Question #717

CISSP Question #717: Real Exam Question with Answer & Explanation

The correct answer is C: It uses clear text and shared secret keys.. RADIUS is a client-server AAA protocol that transmits most attributes in clear text but protects passwords using an MD5 hash combined with a shared secret key. Understanding its authentication mechanism is fundamental to network access security.

Submitted by emma.c· Mar 5, 2026Identity and Access Management

Question

How is Remote Authentication Dial-In User Service (RADIUS) authentication accomplished?

Options

  • AIt uses clear text and firewall rules.
  • BIt relies on Virtual Private Networks (VPN).
  • CIt uses clear text and shared secret keys.
  • DIt relies on asymmetric encryption keys.

Explanation

RADIUS is a client-server AAA protocol that transmits most attributes in clear text but protects passwords using an MD5 hash combined with a shared secret key. Understanding its authentication mechanism is fundamental to network access security.

Common mistakes.

  • A. While RADIUS does transmit some attributes in clear text, it does not rely on firewall rules for authentication; access control is handled by the RADIUS server's policy engine, not network-layer firewall filtering.
  • B. VPNs are a separate tunneling and encryption technology; RADIUS operates independently of VPNs as a dedicated AAA protocol using UDP ports 1812/1813 and does not require a VPN to function.
  • D. RADIUS does not use asymmetric (public/private key) encryption for its authentication process; it relies on a symmetric shared secret combined with MD5 hashing, making asymmetric encryption incorrect for describing its mechanism.

Concept tested. RADIUS authentication mechanism and shared secret usage

Reference. https://datatracker.ietf.org/doc/html/rfc2865

Topics

#RADIUS#authentication protocols#shared secret key#network authentication

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