Single Sign-On (SSO)
What is SSO?
Single Sign-On (SSO) enables users to log in once and access multiple systems or applications using a single set of credentials (such as username and password). This approach enhances user convenience, reduces password related issues, and improves security through centralized identity management.
How does SSO work?
SSO allows users to use a single set of credentials and access multiple apps without re-entering passwords. This works by having a trusted Identity Provider (IdP) that authenticates the user and then generates an authentication token (or assertion) that’s passed to other applications (the Service Providers [SPs]) as a proof of identity.
For example: You sign into Zoho Workplace once, and that same login gives you access to Mail, WorkDrive, Cliq, and Calendar without needing to log in again.
The SSO workflow includes:
Step 1: The user logs in (or is already logged in).
Step 2: The IdP creates an authentication token with the user’s identity information.
Step 3: This authentication token is digitally signed so the SPs can securely verify its authenticity.
Step 4: The SP receives the token and checks the signature and validity. If the details are valid, the SPs lets the user in without asking for the password again.
Consider a real-world scenario on how SSO works between Okta (IdP) and Zoho (SP).
Step | Action | Initiator |
| 1 | User accesses Zoho | User |
| 2 | Zoho redirects to Okta (IdP) | Zoho (SP) |
| 3 | User authenticates with Okta | User → Okta (IdP) |
| 4 | Okta issues a SAML response (assertion) and sends it back to Zoho via the browser | Okta → Browser → Zoho |
| 5 | Zoho validates the SAML assertion | Zoho |
| 6 | Zoho grants access to the user | Zoho → User |
What is an authentication token?
An authentication token is a piece of digital information issued by the Identity Provider once a user logs in successfully. This token contains key details of the user's identity, how long a token is valid, and other attributes. It’s secured cryptographically to prevent any tampering.
Later, when the user moves to other applications (SPs), this token is sent from the IdP to the SP to verify the details. Once the token is verified, the user is successfully granted access without needing to re-enter credentials.
What SSO protocols are used?
SSO protocols are standards established to facilitate the secure sharing of user authentication and authorization of information between Identity Providers and Service Providers. Here are the main protocols used in SSO:
Secure Assertion Markup Language (SAML)
- SAML is an XML-based protocol used for both authentication and authorization.
- It’s commonly used in enterprise environments for SSO and federated identity management.
- In Zoho Workplace, SAML enables smooth SSO, letting you securely access all of your apps with a single trusted login while keeping identity management centralized.
OAuth 2.0
- OAuth 2.0 is an authorization framework that lets users give third-party apps access to their protected data, without sharing passwords.
- It offers a secure, standard way for users to control what they share and for how long.
OpenID Connect (OIDC)
- OpenID Connect is an authentication protocol built on OAuth 2.0 that adds an identity layer that allows apps to verify users securely and obtain their identity details in a standard way.
- It uses JSON Web Tokens (JWTs) to share information between the IdP and the SP.
Kerberos
- Kerberos is a secure, ticket-based authentication protocol that verifies identities over untrusted networks.
- Kerberos uses a central, trusted server to authenticate both users and services.
- Its Key Distribution Center (KDC) issues secure tickets based on stored credentials. This ensures that identities are verified before granting access.
Why do you need SSO?
As businesses increasingly adopt cloud services and mobile technologies, managing user identities becomes more complex, introducing significant security challenges. Relying solely on traditional password systems is no longer sufficient to protect against evolving cyber threats.
Implementing SSO enhances an organization's alignment with best practices in identity and access management, providing a secure, efficient, and user-friendly environment. Additionally, certain industry compliance regulations mandate the adoption of SSO to enhance their security measures.
By eliminating the need for users to repeatedly sign into each application, SSO significantly boosts productivity, allowing employees to focus more on their tasks and less on managing multiple logins.
Advantages of SSO
SSO plays a key role in simplifying access while keeping things secure and efficient for both users and organizations.
Better user experience: No more struggling with multiple logins. One sign-in gives users access to all connected apps, making their day smoother.
Less password fatigue: Fewer passwords mean fewer chances of forgotten credentials or weak, reused ones, which is often a major reason behind security issues.
Stronger security: Centralized login control helps enforce strong password rules, enable Multi-Factor Authentication (MFA), and detect suspicious sign-in activities more effectively.
Reduced IT load: With fewer password resets to handle, IT teams can focus on more critical tasks, saving time and reducing support costs.
Simplified compliance and control: Centralized access control helps monitor user activity, enforce policies, and ensure that compliance with security and data protection standards is met.
Key differences between SSO and non-SSO
Consider a scenario where an organization uses a conventional method of logging in, where users have to insert their credentials every time they access a service or an application. Though this is a common practice found in organizations with a preference for independent authentication with the main focus on security, there are challenges faced compared to organizations that use SSO. Below are the key feature differences observed between organizations with and without SSO.
Key features | SSO | Non-SSO |
| User experience | One login for all apps, faster onboarding, and fewer password resets. | Multiple logins, frequent password resets, and slower onboarding. |
| Security | Centralized login, strong password policies, and MFA for added security. | Increases security risks due to password fatigue, leading users to reuse weak passwords across multiple platforms. |
| Password management | Minimizes password-related IT support requests since users have fewer passwords to manage. | Increases the burden on IT teams because users frequently forget passwords, leading to more password reset requests. |
| Implementation complexity | Requires integration with an identity provider, making initial implementation complex but beneficial in the long run. | Easier to implement because each application manages authentication separately. However, it leads to inefficiencies over time. |
| Compliance and auditability | Enhances compliance with security regulations by providing unified logging and monitoring of user activity. | Makes auditing difficult because user activity is scattered across multiple systems. |
| Cost considerations | While the setup cost may be high initially, it reduces long-term operational costs by minimizing IT support needs. | May seem cost-effective initially but leads to hidden costs in IT effort and security incidents. |
Types of SSO with examples
SSO comes in different forms, each customized to different environments and user needs. Understanding each type helps you choose the right setup that balances user convenience and security. This table explains the SSO solution types with examples.
Types of SSO | Description | SSO examples |
| Cloud SSO | Allows user to log in once and access various cloud-based applications, without the need to re-enter the credentials for each app. | Zoho Workplace SSO (provides single login to access various cloud apps like Mail, Cliq, Calendar, and other apps). |
| SaaS SSO | Provides Single Sign-On for popular SaaS tools like HR, CRM, or collaboration apps. | Okta SSO (provides a single login for apps like Slack, Salesforce, and Zoom). |
| Enterprise SSO | Used inside organizations for on-premises apps, internal portals, and legacy systems. | IBM Security Access Manager, Oracle Identity, Azure active directory. |
| Federated SSO | Enables SSO across organizations or domains by trusting each other’s IdPs. | Using your Google account to log into third-party websites like YouTube or Meta. |
| Mobile SSO | Mobile SSO lets you access multiple apps using your phone’s authentication, like biometrics or device-based approval, instead of typing passwords. | It often works with mobile identity providers like Apple ID or Google Sign-In. |
| Smart card-based SSO | Smart card-based SSO uses a physical card loaded with your sign-in credentials to log in securely. You tap or insert it once for the first login, and after that, no more typing usernames or passwords. | Commonly used in high-security setups like government or healthcare. |
SSO security risks
While SSO is a convenience for users, it poses security risks at the enterprise level. These risks include:
Single point of failure: Centralized authentication leads to all dependent services being inaccessible if the SSO system fails due to an outage or breach.
Credential phishing: If your SSO credentials are exposed to attackers, they get a master key which grants them immediate access to all connected systems.
Token theft: Stolen tokens let attackers bypass authentication altogether, maintaining access as long as the token remains valid.
Supply chain risk: If a third-party provider suffers a breach or significant vulnerability, it could potentially affect all of its customers. This phenomenon is called supply chain risk. This shows how an organization's security is dependent on the security of its external vendors.
Excessive access privilege: Using the same access rules for all of the systems risks giving users more permission than they actually need, opening security gaps.
SSO best practices
Following SSO best practices ensures secure authentication and reliable access across all systems, while minimizing risk for your organization. Key best practices include:
Enable multi-factor authentication: MFA challenges threats like phishing, brute-force attacks, and credential stuffing by demanding more than a password, like a biometric or a trusted device, making unauthorized access much harder.
Limit access with least privilege: Granting admin rights to everyone turns out to be a security risk. You can use role-based or attribute-based access, and regularly review permissions to avoid over-privileged users.
Set timed sessions and tokens: Set session timeouts, limit concurrent logins, auto-expire idle sessions, and rotate/revoke tokens quickly if something seems suspicious to avoid further exposure to a possible threat.
Monitor and audit continuously: Keep an eye on odd login behaviors like failed attempts, logins at odd hours, or logins from unfamiliar locations. Audit permissions regularly, so no one has more access than necessary. Centralizing your logs helps you stay audit-ready and able to catch threats quickly.
Use standard protocols and plan backup: Stick to proven SSO standards like SAML or OIDC because they're interoperable and secure. Always build in fallback mechanisms, like backup identity providers or automatic fail overs, so that authentication keeps flowing even if your primary IdP fails.
The best practices outlined above are not exhaustive. However, adopting SSO and adhering to widely followed best practices will significantly enhance the security posture of your organization.