What is SSO (Single Sign-On)?

Single sign-on authentication or SSO allows users to log in once to access multiple applications, services and accounts, and across different domains. With SSO, a user only has to log in once with their log-in credentials (username and password etc.) to access their SaaS applications. Using SSO means that a user does not have to authenticate for every app they log into. For example, if you log into a Google service such as Gmail, then you are automatically authenticated to other Google apps such Youtube, AdSense, Google Analytics, etc.
It should be noted that there is a significant difference between single sign-on and same sign-on. Single sign-on authentication (SSO) refers to systems where a single authentication provides access to multiple applications by passing the authentication token seamlessly to configured applications. Same sign-on, also known as Directory Server Authentication, refers to systems requiring authentication for each application but using the same credentials from a directory server. Single sign-on is known to be a framework and normally referred to as a solution. Generally, when people say an SSO solution, they are also talking about a software as the words can be used interchangeably.

Advantages and Disadvantages of SSO


  • Stronger Unified Authentication
    • Users will only have to remember one password, versus multiple passwords across different applications.
    • Better password policy enforcement to ensure maximum security
    • Single point for enforcing password re-entry
    • Enforce Multi-factor authentication in one place
    • Less time wasted on password recovery should a user forget their password
      Example: A strong password is not easily guessed and is random enough that a brute force attack is not likely to succeed. E.g w7:g”5h$G@ is considered to be a strong password; whereas password123 is not.


  • Security & Compliance
    • A comprehensive single sign-on security solution is important for reducing your attack surface
    • It’s also a widely used control for meeting a variety of compliance standards.
    • Compliance regulations often require that controls be put in place around data protection
    • Example: SOC 2 and HIPAA, are organizations that require security compliance standards and SSO meets those requirements.


  • Boosting Productivity
    • In settings such as hospitals, defense industries, and emergency services, where large numbers of people and departments demand rapid and uninterrupted access to the same applications, SSO prevents errors and malware intrusion which can be the difference between life and death.


  • Security Risks
    • When SSO is down, access to all connected sites is stopped.
    • SSO is risky for multi-user computers
    • Some SSO-linked sites may give their user data to third-party entities.
    • When your identity provider goes down, SSO does too.
    • Although single sign-on is a convenience to users, it presents risks to enterprise security.
    • An attacker who gains control over a user’s SSO credentials will be granted access to every application the user has rights to, increasing the amount of potential damage.
    • It does not address certain levels of security each application sign-on may need.

How Does SSO Work?

SSO works based upon a trusting relationship set up between an application, (service provider), and an identity provider, (such as, Active Directory Federation Services). This trust relationship is often represented by a certificate that is exchanged between the identity provider and the service provider. This certificate is used as the key to verify identity information that is being sent from the identity provider to the service provider. This tells the service provider that the identity is coming from a trusted source. With Single Sign-On (SSO), this identity data takes the form of tokens that contain identifying bits of information about the user like a user’s email address or username.

Here is how the SSO process works:

  1. User browses to service provider
  2. Request sent to users browser
  3. Access requested
  4. User logs in (if necessary)
  5. Token sent to user’s browser
  6. Token sent to Apps endpoint with the users identity
  7. Response received and the user is validated
  8. Access granted

What is an SSO Token?

An SSO token is a collection of data or information that is passed from one system to another during the Single sign-on process. The data can be as simple as a user’s email address and information about which system is sending the token. Tokens must be digitally signed for the token receiver to verify that the SSO token is coming from a trusted source. The certificate that is used for this digital signature is exchanged during the initial configuration process.

How does SSO fit into an access management strategy?

SSO is just one aspect of managing a user’s access. SSO must be combined with access control, activity logs, permission controls, and other measures for tracking and controlling user behavior within an organization’s internal systems. If the SSO system doesn’t know who a user is, then there is no way for it to allow or restrict a user’s access.

Types of SSO Configurations

SAML-based SSO (Security Assertion Markup Language): is an online service provider that can contact a separate online identity provider to authenticate users who are trying to access secure content. SAML allows secure web domains to exchange user authentication and authorize data.

Smart card-based SSO: will ask an end-user to use a card holding the sign-in credentials for the first login. Once used, a user will not have to re-enter usernames or passwords.

Kerberos-based setup: is a system where once the user credentials are provided, a ticket-granting ticket (TGT) is issued. The TGT that is issued, gathers service tickets for other applications that the user wants to access without asking the user to re-enter their credentials multiple times.

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