What is Single Sign-On (SSO)?

Single Sign-On (SSO) is an authentication mechanism that allows users to access multiple connected applications after authenticating once, without signing in separately to each application. A trusted identity provider (IdP) typically authenticates the user and allows connected applications to rely on that authentication.

SSO reduces repeated login prompts and allows organizations to manage authentication policies centrally across integrated applications.

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How does Single Sign-On work?

SSO allows applications to trust authentication performed by a central identity provider. In a typical federated SSO flow, the application redirects the user to the IdP, which authenticates the user and returns an authentication response that the application validates.

Access request

A user opens an SSO-enabled application. If the application does not have a valid session, it redirects the user to the identity provider.

Identity verification

The IdP authenticates the user through credentials, multi-factor authentication (MFA), or another configured method. If a valid IdP session already exists, another login may not be required.

Authentication response

The IdP provides an authentication assertion or token using a supported protocol, which the application receives and validates.

Application access

The application checks the authentication response and applicable access permissions before establishing a session.

Once authenticated, the user can access other connected applications without signing in again, provided the existing authentication session and access policies permit it.

What are the key components of SSO?

SSO relies on several components that authenticate users and allow connected applications to trust a central identity provider.

Identity Provider (IdP)

Authenticates users and provides identity information to connected applications.

Service Provider (SP)

An application or service that relies on the IdP's authentication response to establish a user session. In OpenID Connect, this role is commonly called a relying party.

User directory

Stores or provides access to user identities and attributes. Organizations may use directories such as Microsoft Active Directory.

Authentication assertion or token

Carries authentication or identity information that applications validate before establishing a session.

Which protocols are used for Single Sign-On?

SSO uses authentication protocols that allow identity systems and applications to exchange and validate authentication information.

Security Assertion Markup Language (SAML 2.0)

An XML-based standard that enables identity providers to send authentication tokens to service providers. It is commonly used for enterprise web applications.

OpenID Connect (OIDC)

An authentication protocol built on OAuth 2.0 that allows applications to verify a user's identity using information from an identity provider, including ID tokens.

Kerberos

A network authentication protocol that uses tickets to authenticate users and services without repeatedly transmitting passwords. It is commonly used in Windows domain environments.

OAuth 2.0 is an authorization framework, not a standalone authentication protocol. It enables applications to obtain delegated access to resources, while OIDC extends OAuth 2.0 to support user authentication.

What are the benefits of Single Sign-On?

SSO simplifies application authentication for users while allowing organizations to manage sign-in requirements centrally.

Reduced password fatigue

Users maintain fewer application-specific credentials, reducing the need to remember multiple passwords.

Simplified application access

Employees can move between connected applications without repeatedly entering login credentials that would interrupt their workflow.

Centralized authentication policies

IT teams can apply consistent sign-in requirements, including MFA, through the identity provider across connected applications.

Better authentication visibility

Centralized sign-in records help IT administrators monitor authentication activity across integrated applications.

Lower IT support overhead

Fewer application-specific credentials can reduce password-related support requests.

What are the limitations and security risks of SSO?

Although SSO simplifies authentication, centralizing access also introduces security and operational considerations.

Identity provider availability

Applications that depend on an IdP may experience authentication disruptions when the identity service is unavailable.

Application compatibility

Legacy applications that do not support modern federation protocols may require alternative integrations or separate authentication.

Session and token theft

Attackers who obtain valid authentication sessions or tokens may be able to access connected applications without repeating the initial authentication process.

Integration and configuration complexity

Incorrect trust configurations, inconsistent user provisioning, or unsupported logout behavior can create access-management gaps.

Single point of failure

A compromise of the identity provider or an SSO account may expose multiple connected applications, depending on the affected identities, permissions, and security controls.

Organizations can reduce these risks by enforcing MFA, protecting authentication sessions, monitoring suspicious sign-ins, maintaining reliable identity infrastructure, and applying appropriate access controls.

SSO vs. Traditional Authentication: What's the difference?

With traditional authentication, users typically sign in to each application separately. SSO allows connected applications to rely on authentication performed by a trusted identity provider.

Aspect Traditional authentication Single Sign-On (SSO)
Login process Users sign in to each application separately Users authenticate once to access various applications and websites
Credentials Applications may require separate credentials Applications can rely on a shared authentication session or supported credential integration
Authentication management Managed independently by applications Centralized through an IdP
Security policies May differ across applications Can be enforced centrally through the IdP
User experience Repeated login prompts Fewer sign-ins

How does SSO fit into Identity and Access Management?

Single Sign-On is an authentication capability within Identity and Access Management (IAM).

While SSO allows users to authenticate across connected applications, IAM covers the broader management of digital identities, application permissions, user provisioning, and access throughout the identity lifecycle.

SSO works alongside other IAM capabilities, including MFA, role-based access control (RBAC), identity provisioning, and access reviews. Together, these capabilities help organizations manage who can access resources and under what conditions.

Common use cases of Single Sign-On

SSO is useful when users need to access multiple connected applications without signing in to each one separately.

Enterprise application access

Employees authenticate through their organization's identity provider to access approved email, CRM, HR, and collaboration applications.

Education

Students, teachers, and administrative staff use a central identity system to access learning platforms, student portals, and institutional applications.

Customer and partner portals

Businesses allow authenticated customers and partners to move between connected services without maintaining separate application logins.

What should organizations look for in an SSO solution?

An SSO solution should support an organization's applications, identity infrastructure, and authentication requirements.

Application compatibility

Support for commonly used SaaS, on-premises, and legacy applications.

Authentication protocol support

Compatibility with standards such as SAML 2.0 and OIDC.

MFA integration

Support for additional authentication factors and conditional sign-in requirements.

Directory and IAM integration

Compatibility with existing identity directories, user provisioning processes, and access-management systems.

Session management and monitoring

Visibility into authentication activity and controls for managing user sessions.

Reliability and availability

Infrastructure capable of maintaining authentication services and supporting recovery during disruptions.

Organizations managing employee endpoints may also consider SSO solutions that support device-based access conditions.

Single Sign-On with Scalefusion OneIdP

Scalefusion OneIdP provides Single Sign-On for integrated business applications, enabling organizations to centralize user authentication and manage access policies.

Through its integration with Scalefusion Unified Endpoint Management (UEM), OneIdP supports conditional access policies that can consider whether a device is managed by Scalefusion while supported configurations can also use device-related conditions when evaluating access to integrated business applications.

With identity and device management connected through a centralized dashboard, IT admins can configure SSO policies and managed-device access conditions centrally by connecting application authentication with endpoint management.

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Frequently asked questions

1. Is SSO the same as MFA?

No. SSO allows users to access multiple connected applications after authenticating once, while multi-factor authentication (MFA) requires users to verify their identity using two or more authentication factors.

The two can work together, with MFA applied during the initial SSO authentication or when additional verification is required.

2. What is the difference between SSO and federated identity?

SSO allows users to access multiple connected applications after a single authentication. Federated identity enables separate systems or security domains to trust identity information or authentication performed by another identity provider.

Federation can support SSO across different applications and organizations, but the two concepts are not interchangeable.

3. Is Single Sign-On secure?

SSO can improve authentication security by reducing application-specific passwords and supporting centralized policies such as MFA and conditional access.

However, its security depends on the identity provider, application configuration, session protection, and access controls. A compromised SSO account or session may expose multiple connected applications.

4. Does SSO automatically give users access to every connected application?

No. SSO simplifies authentication but does not automatically grant permission to every connected application.

Users can access only the applications and resources permitted by their assigned roles, application access settings, and applicable authorization policies.

Access work applications with conditional single sign-on for better security.

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