Authentication, Authenticity or Non-Repudiation?

About this interactive

Authenticity and non-repudiation extend the CIA triad into the five pillars, and both are easy to confuse with authentication. Authentication is proving who you are to a system so it lets you in: a username and password, a code on your phone, a badge and PIN, a fingerprint. It happens at the door. Authenticity is about a message or file once it arrives. Susan sends David a memo; authenticity means David can be sure it came from Susan and not from someone posing as her. It is the receiver's question: where did this come from? Non-repudiation is the same exchange seen from the sender's side. If Susan later says she never sent the memo, non-repudiation is what stops her: evidence, usually a digital signature made with her private key, that ties the message to her. It matters when there is a dispute. One digital signature can give authenticity, integrity and non-repudiation at once, so do not sort by the word "signature". Ask what the situation is about: getting in, trusting the origin, or holding the sender to it.

What you'll learn

Distinguish authentication, proving who you are to a system to gain access, from authenticity, the receiver being able to trust where a message came from
Distinguish authenticity, which lets the receiver confirm the sender, from non-repudiation, which leaves the sender unable to deny sending it

Aligned to

CompTIA Security+

1.2 Summarize fundamental security concepts.

Key terms

Authentication: The process of verifying the identity of a user, device, or system.
Authenticity: The assurance that information or a communication originates from the claimed source and has not been fabricated or impersonated. Digital signatures and certificates are common mechanisms for establishing authenticity.
Non-repudiation: The assurance that a party cannot deny having sent or received a message or performed an action.
Digital Signature: A cryptographic mechanism used to verify the authenticity and integrity of a digital message or document.
Multi-Factor Authentication: An authentication method that requires users to provide two or more verification factors to gain access.
Public Key Infrastructure: A framework of hardware, software, policies, and standards used to create, manage, and distribute digital certificates.

Topics

Interactive Categorize

About TechKnowSurge

TechKnowSurge builds IT and cybersecurity professionals through hands-on, concept-first training built around real understanding — not memorization. Free interactive tools, structured programs, and 25+ years of real-world experience, all in one place.

Explore free tools and programs →