An organization utilizes multiple vendors, each with its own portal that a security analyst must sign in to daily. Which of the following is the best solution for the organization to use to eliminate the need for multiple authentication credentials?

Single Sign-On (SSO) is an identity and access management (IAM) solution that allows a user to authenticate once and gain access to multiple applications or systems. An identity provider (IdP) manages the authentication process. After successful authentication with the IdP, the user can access various vendor portals (service providers) without needing to log in to each one separately. This directly addresses the scenario's requirement to eliminate the need for multiple authentication credentials, improving both user experience and security by centralizing credential management.

A. API: An Application Programming Interface (API) is a set of protocols for building and integrating application software. It is not an authentication system for end-users.
B. MFA: Multi-Factor Authentication (MFA) adds layers of security to a single login process. It does not reduce the number of credentials needed for different systems.
D. VPN: A Virtual Private Network (VPN) provides a secure, encrypted connection to a private network over a public one. It is for network access, not application authentication.

1. National Institute of Standards and Technology (NIST). (2017). NIST Special Publication 800-63-3: Digital Identity Guidelines. Section 2, Definitions, page 8. "Single Sign-On (SSO) - An authentication process that, when completed, allows a subscriber to access a set of related but independent software systems without having to authenticate separately to each system." (https://doi.org/10.6028/NIST.SP.800-63-3)

2. Purdue University. (n.d.). Information Technology at Purdue (ITaP) - Identity and Access Management Concepts. "Single Sign-On (SSO) is a session and user authentication service that permits a user to use one set of login credentials (e.g., name and password) to access multiple applications." Retrieved from Purdue University's official documentation on IAM.

3. Massachusetts Institute of Technology (MIT). (2018). 6.857 Computer and Network Security, Fall 2018 - Lecture 18: Web Security. The lecture notes discuss authentication protocols like SAML (Security Assertion Markup Language) which are foundational technologies for implementing SSO systems between different organizations (identity providers and service providers).