For modern developers, securing user data is more critical than ever. Ensuring that your applications implement reliable and effective authentication methods is a fundamental part of protecting both your users and your system.
Password Authentication Protocol (PAP) serves as a starting point in understanding how to authenticate users. As one of the simplest such protocols, understanding how PAP works provides a foundation for a developer’s understanding of authentication.
In this article, we will provide a high-level overview of PAP, surveying its role in application security as well as its limitations. We’ll see how leveraging platforms like Auth0 can help you to implement secure, scalable authentication, freeing you to focus on the best experience possible for your users.
So What Is It?
Password Authentication Protocol (PAP) is a method for authenticating human users (or devices, service accounts, etc.) by verifying their credentials.
PAP is used with Point-to-Point Protocol (PPP). PPP is a data link layer protocol used to establish direct communication between two network nodes. PPP supports various authentication protocols, as we shall see. Before establishing a network connection between the two nodes (client and server), the identity of the client must first be verified via one of these supported protocols.
PAP is just one of the protocols that PPP supports and is one of the simplest to understand. As we will see, PAP has its drawbacks, but its strength is its simplicity.
Password Authentication Protocol (PAP) vs. Challenge Handshake Authentication Protocol (CHAP)
PAP is a two-way handshake: a client requests authentication, and a server responds. Passwords are delivered in plain text. The system then verifies that the credentials match what is stored for that user and responds with an ack or nack as appropriate.
You may begin to see a problem here. Since the password is sent across the network as regular text, PAP is not the most secure method.
In contrast to the two-way handshake and plain text password of PAP, CHAP is a three-way handshake process.
In a system that uses CHAP, the server first sends a “challenge” to the client. This challenge could be a random string. The client then combines the challenge string with the user’s password and sends back a hash of the combination. If the client’s hash of the challenge + password combo matches the server’s, the user is authenticated.
As we can see, the CHAP process is more secure than PAP since the password itself in plain text is never sent across the network; only the challenge + password hash is. If that hash were to be intercepted, the hacker would not necessarily be able to decipher the user’s password. To provide additional security, the “challenge” word can be rotated periodically to ensure that if the challenge word were to be leaked or deciphered, the hacker would not be able to use it indefinitely to intercept and decipher traffic.
Why Use PAP?
Now that you understand what PAP is and why CHAP can provide an extra layer of security, you may wonder, why use PAP at all?
Unfortunately, some systems, like certain legacy systems, may not support CHAP as a protocol. Some systems may also use multiple vendors under the hood when authenticating, each with differing CHAP variations, complicating implementations. In these cases, we may elect to use PAP in combination with some other layer or layers of security.
A hybrid approach is also an option: authenticate via the CHAP process if possible, but fall back to PAP if the CHAP method fails.
When using PAP, it is important to be aware of its limitations. It is a good idea to provide encryption at another layer of your system, for example, via SSL, TLS, or VPN.
PAP and Auth0
While PAP is a foundational authentication method, as we have seen, its simplicity can pose security risks in modern applications. Implementing a robust and scalable authentication layer to your application can be difficult and time-consuming.
That’s where Auth0 comes in. With Auth0, you can easily implement and manage authentication in your application securely. Auth0 abstracts away the intricacies, saving valuable developer time while ensuring the highest security standards for your users.
Recap
In this article, we learned about PAP and CHAP, their strengths and limitations, and when to use each of them. Now that you have a basic foundation on authentication protocols, you may wish to explore more via the links provided below.
