What is Single Sign-On (SSO)?

In this article, we will introduce basic information about single sign-on (SSO), such as its mechanism, types, advantages and disadvantages. If you would like to deepen your understanding of SSO, please refer to this article.

David Demir

David Demir

18 May 2025

What is Single Sign-On (SSO)?

Single Sign-On (SSO) refers to an authentication method widely used in medium to large enterprises and organizations, allowing users to access multiple systems and applications with a single login.

This system is particularly favored for its convenience in managing user authentication across various platforms seamlessly. In this article, we will introduce the fundamentals of Single Sign-On (SSO), including its mechanism, types, and pros and cons.

What is Single Sign-On (SSO) ?

Single Sign-On (SSO) is an authentication system extensively utilized in medium to large enterprises and organizations. It enables users to access multiple systems and applications with a single login credential.

For instance, using Microsoft Enterprise single sign-on (SSO), employees can access not only Microsoft services but also other third-party services like Salesforce, Google Workspace, and Slack, all configured to integrate with SSO using their company-assigned email addresses (e.g., username@companyname.com) and passwords. Upon logging in via SSO, the user's organizational settings and access permissions are automatically applied.

How Does SSO Work?

Mechanism of SSO Let's delve into how SSO is implemented. The basic process of SSO can be divided into several stages, regardless of the specific implementation method. Here’s a general workflow:

Initial Setup:

User Access and Redirection:

Authentication Process:

Token Generation and Transmission:

Token Validation and Permission:

Session Management:

Single Logout (SLO):

Security and Monitoring:

Types of Single Sign-On (SSO)

Types of Single Sign-On (SSO) SSO employs various protocols, each suited to different environments and requirements. Here are some common SSO protocols:

SAML (Security Assertion Markup Language)

What is SAML and How Does It Work?
SAML (Security Assertion Markup Language) enables secure, seamless access to multiple applications by exchanging authentication data between an Identity Provider (IdP) and a Service Provider (SP).

Operational Flow

SAML

SAML offers several advantages. It provides a high level of security, which is crucial for enterprise applications. Additionally, it allows for the exchange of detailed attribute information, giving Service Providers more context about the authenticated user.

OAuth 2.0:

OAuth 2.0

OAuth 2.0 supports multiple grant types to accommodate different scenarios.

These include the Authorization Code Flow, which is suitable for server-side applications. The Implicit Flow is designed for client-side applications. The Resource Owner Password Credentials grant type is used when there's a high level of trust between the user and the client.

Lastly, the Client Credentials grant type is employed for machine-to-machine communication where user involvement isn't necessary.

OpenID Connect (OIDC):

OIDC

Flow

  1. The client sends an authorization request
  2. The user authenticates and authorizes
  3. An authorization code is returned
  4. The client obtains an access token and an ID token.
  5. Get User Information (Optional)

Each of these protocols is suited to different use cases and requirements, so it is important to choose the right protocol based on your organization's needs and existing infrastructure.

Advantages and Disadvantages of SSO

As outlined, SSO offers numerous benefits such as improved user convenience, enhanced security, reduced management costs, increased productivity, compliance improvements, easy integration with new applications, risk mitigation for security incidents, and consistent authentication across devices.

However, it also presents challenges like being a single point of failure, concentrated security risks, complexity and initial costs of implementation, vendor lock-in, user dependency, privacy concerns, compliance complexities, session management issues, and the complexity of integrating MFA effectively.

Conclusion

Single Sign-On (SSO) is crucial in modern digital environments for balancing user convenience with enhanced security. Understanding its mechanisms, types, and the pros and cons helps organizations choose the right solution based on their needs.

Implementing SSO effectively can significantly improve efficiency and security within an organization, but it requires ongoing security measures and user education to maximize its benefits.

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