Certified: The Security+ Prepcast

In this episode, we are going to explore two essential topics: non-repudiation and the A A A framework, which stands for authentication, authorization, and accounting. These concepts are foundational in cybersecurity because they ensure that access and actions can be verified, validated, and recorded. In other words, they help answer the critical questions: Who did what? When? And how can we prove it?
Let’s begin with non-repudiation. This term means that someone cannot deny their actions or communication. In the context of cybersecurity, non-repudiation ensures that a person or system cannot later claim they did not send a message, make a change, or access a resource. It is about holding users accountable and making digital actions legally and operationally undeniable.
Non-repudiation plays a major role in both legal and security contexts. In legal terms, it supports compliance and evidence collection. For instance, if someone signs a digital contract, non-repudiation ensures that the signature can be tied to that person without question. In a security setting, it helps organizations trace actions back to specific users or systems, which is essential during investigations, audits, and incident response.
Several tools support non-repudiation. One of the most important is the digital signature. A digital signature uses cryptographic techniques to bind a person’s identity to a digital message or document. If someone sends an email with a digital signature, that signature can be independently verified to confirm the sender’s identity and that the message has not been altered. It provides strong evidence of origin and integrity.
Certificates are another tool used to establish non-repudiation. A digital certificate is issued by a trusted certificate authority and links a public key to an individual or organization. When someone uses a certificate to sign a message or establish a secure connection, they are providing verifiable proof of identity.
Audit trails also support non-repudiation. An audit trail is a detailed record of system activity, showing who accessed what resources and when. For example, if a sensitive file is downloaded, the audit log might show the exact user account, the time of access, and the device used. This makes it difficult for someone to later deny their involvement.
Consider an example where non-repudiation becomes critical. In a healthcare setting, a doctor prescribes medication through a digital portal. If that prescription is later challenged or questioned, the system must be able to prove that the doctor, and no one else, submitted it. Digital signatures, tied to their secure credentials, provide that proof. Without non-repudiation, it would be impossible to trace actions or resolve disputes with confidence.
Now let’s move to the A A A model—authentication, authorization, and accounting. These three components are often implemented together to control access to systems and to ensure accountability.
Authentication is the first step. It means proving that someone is who they claim to be. There are many methods of authentication. Biometrics rely on physical characteristics, like a fingerprint or facial recognition. Multi-factor authentication requires two or more methods—such as a password and a fingerprint—to add layers of security. Digital certificates are also used in authentication. They prove a user’s identity using encrypted credentials issued by a trusted source.
Good authentication is essential because it is the foundation of every secure session. If you cannot prove who a user is, you cannot control what they do or track their actions reliably. That is why strong authentication, especially multi-factor authentication, is considered a best practice in modern cybersecurity.
Once a user has been authenticated, the next step is authorization. This determines what the user is allowed to do. For example, after logging in, a finance department employee may be able to view and update payroll data, while a sales representative may only be able to view sales reports. Both are authenticated users, but their access is limited based on their roles.
There are several models of authorization. Role-based access control assigns permissions based on a user’s job function. This is common in large organizations where many users share similar responsibilities. Rule-based access control uses specific rules—such as “only allow access during business hours”—to decide what users can do. Attribute-based access control considers a wide range of factors, like user department, location, and current project. These models provide flexibility and help organizations manage permissions efficiently.
The third part of the model is accounting. This refers to tracking what users do after they log in. Accounting is achieved through tools like audit logging, which records actions such as file access, system changes, or login attempts. This data is used for monitoring, troubleshooting, and investigation. If a security incident occurs, accounting records help determine exactly what happened and who was involved.
Accounting processes are also important for compliance. Many regulations require organizations to log and review system activity regularly. Without accounting, it is difficult to enforce policies or respond to incidents. For example, if an employee downloads confidential documents before resigning, accounting logs can provide the evidence needed to take appropriate action.
To bring all of this together, think of the A A A model as a layered process. First, verify identity through authentication. Then, grant appropriate access through authorization. Finally, keep track of what happens through accounting. Together, these steps support security goals like confidentiality, integrity, and non-repudiation.
As you study for the Security Plus exam, make sure you can clearly define each part of the A A A framework. Be able to identify examples of authentication, such as biometrics or certificates. Understand how role-based and attribute-based models differ in their approach to authorization. And know how accounting logs and audit trails are used to support security and compliance. The exam may ask you to recognize these components in scenario-based questions, so practice applying them to real-world situations.