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CompTIA Security+ 4.6 ISC2 CISSP 5.6 NIST 800-53 IA-2 NIST CSF PR.AA-03 CompTIA Security+ 1.2 CompTIA SecurityX 2.1
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Authentication Protocols

Authentication protocols define how users, devices, and services verify their identity before gaining access to a network, device, or resource. This topic covers the core protocols used in point-to-point connections and AAA (Authentication, Authorization, and Accounting) frameworks.

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About this video

Authentication protocols are the standardized methods that enable a user, device, or service to prove its identity before being granted access to a protected resource. Those resources can span a wide range — a network, a specific device on that network, a service, a file share, an individual file, or a peripheral like a printer. On the requesting side, access may come from an end user at a workstation, a managed device such as a laptop or server, or an automated service communicating with another system. Regardless of the combination, a protocol must exist to carry the credential exchange between the two parties. Point-to-point protocols handle authentication at the direct connection level. The Point-to-Point Protocol itself operates at Layer 2 and is used to establish a link between two devices — for example, router-to-router connections where sensitive routing information will be exchanged. Before that exchange begins, the devices authenticate each other using protocols such as PAP, CHAP, or EAP. The same authentication requirement applies in a broader sense any time two machines on a shared network need to verify each other before communicating. AAA protocols serve a different purpose: rather than authenticating a direct connection, they route credential verification to a centralized backend server. In environments with thousands of routers or network devices, storing credentials locally on each device is unmanageable. AAA protocols solve this by forwarding login attempts from a device to a dedicated authentication server, which then approves or denies access and returns the result. This centralized model makes large-scale user management practical and is a cornerstone of enterprise network security architecture.

What you'll learn

What's covered

Authentication Protocols

Aligned to

CompTIA Security+
4.6 Given a scenario, implement and maintain identity and access management.
1.2 Summarize fundamental security concepts.
ISC2 CISSP
5.6 Implement authentication systems
NIST 800-53
IA-2 Identification and Authentication (Organizational Users)
NIST CSF
PR.AA-03 Users, services, and hardware are authenticated.
CompTIA SecurityX
2.1 Given a scenario, analyze the security requirements and objectives to provide the appropriate authentication and authorization controls.

Key terms

Authentication
The process of verifying the identity of a user, device, or system.
Protocol
A set of rules governing the format and transmission of data between devices.
Point-to-Point Protocol
PPP
A data link protocol used to establish a direct connection between two nodes.
Authentication, Authorization, and Accounting
AAA
Authentication, Authorization, and Accounting is a security framework that controls network access by verifying user identity, determining permitted actions, and logging activity for auditing and billing purposes.
Password Authentication Protocol
PAP
A simple authentication protocol used with PPP that transmits usernames and passwords in plaintext over the connection. PAP is considered insecure because credentials can be intercepted by anyone monitoring the link and has been replaced by CHAP and EAP in modern implementations.
Challenge Handshake Authentication Protocol
CHAP
Challenge Handshake Authentication Protocol is a three-way authentication method in which the authenticator sends a challenge, the peer responds with a hash of the challenge and shared secret, and the authenticator verifies the response without transmitting the password in cleartext.
Extensible Authentication Protocol
EAP
Extensible Authentication Protocol is a flexible authentication framework used in wireless networks and PPP connections that supports multiple authentication methods including certificates, tokens, and passwords.

Topics

Authentication Protocols Aaa Frameworks Network Security Identity Verification Point To Point Protocols Networking

Transcript

In order to grant access into some sort of resource, we better go through some sort of authentication process. We better do a verification process to ensure whatever user or device that's accessing this resource has permission to access that resource.

What we're gaining access to could be any number of resources. It might be the network, or it could be a device on that network, or a service that's running on that device. Maybe it's a file share. Maybe it's the file itself. Maybe it's a printer. Any number of resources; there's lots of different resources. So it could be any of these resources that we're authenticating to get into.

On the other side, we could be granting access to a device. Maybe it's a laptop or desktop or a server. Maybe we're accessing it from a user, whoever's on that system, and gaining access by a user that they have access to these resources. Or maybe it's by a service, so we could have a service that's running on this machine that's talking to another service or talking to the network, or whatever the case may be. So we can have any number of what needs the access to what resource it is.

In order to carry this out, we need some sort of protocol that allows this authentication, some sort of verification where this user says, "Hey, I would like access to this resource." And this resource is, "Okay, well, show me your credentials to do that." There's this communication that happens, these protocols that are being sent back and forth for this device or user or service to say, "Yes, this is who I am," and then this resource to verify that okay, you can have access to this resource.

There are a lot of different protocols. The wiki article breaks it up into kind of three sections: point-to-point protocols, AAA protocols, and other. But there are a lot of other protocols; this is just a sample of some of the protocols that are out there. The main ones that we're going to be focusing on here are going to be these protocols that get incorporated actually into a lot of these other types of protocols.

Point-to-point

When it comes to authentication, point-to-point can mean a couple of things. One, there's an actual protocol called point-to-point protocol. With this point-to-point protocol, maybe two devices want to speak with each other, or make a connection. This would be an alternative to Ethernet, so this is a layer 2 protocol to establish this link and this connection. Maybe it's router to router, and these routers are going to exchange sensitive routing information, so they're going to connect point-to-point protocol, but before they connect and start exchanging the sensitive information they need to authenticate each other. So they're going to use something like PAP, or CHAP, or maybe it's EAP, to start this communication and authenticate each other before they set up an actual full-on connection.

The other type of point-to-point would just be in the general sense of one machine talking to another machine. Even if it's not directly, maybe it's on a shared network from a layer 2 perspective, but these two machines want to talk with each other. Now they're going to need to use one of these same protocols to do an authentication to verify each other.

AAA protocols

AAA protocols serve a little different purpose. Let's say I want to SSH into the router. Many times those router credentials are stored right on the router. But imagine now if I have thousands of routers and I need to remove and add certain users to those routers: this would be a very problematic method. So instead, what I might want to do is authenticate to some sort of database. If there's a database on this back end that's going to be authenticated to, we need a protocol that facilitates this communication right there. That's what AAA protocols are: they facilitate this communication. So the way this would work is I would then SSH into this router, or at least attempt to, and I'd put in my credentials, and this router would send that then to this AAA server, and then respond back and either allow or deny me to get onto that router. So that would be AAA protocols, the purpose for those.

There is this extensive list of authentication protocols, both because we've developed them over time, but there are also different use cases for each one of these. So I'm not going to get into all of these, but just know that this is what authentication protocols are: the protocols that are set up to communicate between two devices for authentication purposes.

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