What is a nonce in cybersecurity, and how does it prevent replay attacks? Learn how using a unique, random value for each login request enhances authentication security—essential for CompTIA Security+ (Plus) SY0-701 exam success.
Table of Contents
Question
A security engineer implements a mechanism where each login request includes a random value that cannot be reused. Which security measure is being used?
A. HMAC (Hashed Message Authentication Code)
B. Salting
C. Rainbow tables
D. Public key cryptography
E. Nonce
Answer
E. Nonce
Explanation
A nonce (number used once) prevents replay attacks by ensuring that authentication requests are unique and cannot be reused.
The security measure being used is a nonce.
A nonce (number used once) is a random or pseudo-random value generated for each authentication request or transaction.
Its primary purpose is to ensure that every login or transaction request is unique, preventing attackers from successfully replaying previously intercepted requests (replay attacks).
When a nonce is included with each login attempt, the server checks that the value has not been used before. If an attacker tries to reuse a previous request (even with valid credentials), the server will reject it because the nonce is no longer valid.
Nonces are widely used in authentication protocols, cryptographic operations, and secure communications to maintain session uniqueness and enhance security.
For maximum effectiveness, nonces must be unpredictable and never reused. They are commonly used in protocols such as TLS, SSH, and digital signature schemes to ensure message integrity and authenticity.
A nonce is a unique, one-time value included in each login request to prevent replay attacks and ensure every authentication attempt is distinct and secure.
CompTIA Security+ (Plus) SY0-701 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the CompTIA Security+ (Plus) SY0-701 exam and earn CompTIA Security+ (Plus) SY0-701 certification.