What Is Single Sign-On?


With the average cost of a data breach at $3.86 million, more businesses are looking for ways to strengthen the security of their networks and applications. Passwords are especially vulnerable because many internet users reuse their passwords for multiple accounts. 

Although password hacks are a common way for hackers to breach company security, you can protect your business from these issues. Single sign-on (SSO) is a commonly-used solution for managing user identities and access. Incorporating SSO can help your organization handle passwords and accounts more securely, reduce IT costs and save time during login. 

What Is SSO? 

You’re likely managing hundreds if not thousands of passwords for your enterprise’s resources. Protecting and keeping track of these passwords can be a monumental task, even for a dedicated IT team. For many organizations, SSO authentication is the solution. 

Single sign-on is a technology that allows the user to use the same set of login credentials across multiple applications and websites. These credentials are often a name and password the user enters once on a single page. SSO technology then securely authenticates the information to verify the user’s identity before allowing them into other applications. With SSO, users can make and use one set of credentials across every application they use. 

What Is the Purpose of Single Sign-On? 

The primary role of SSO technology is to help small enterprises and internet users at large manage their accounts and passwords more easily. If an internet user has to verify their identity each time they want to access a service, they could spend a lot of time and energy remembering and inputting passwords. Many people prefer to use a handful of passwords across multiple applications, making their login credentials easier to remember but more vulnerable to hackers. 

Having an increased number of passwords also puts users’ identities at risk. Individual passwords occur more frequently and are therefore less secure as the number of passwords used across the internet grows. Instead, SSO reduces the sets of login credentials a user needs to authenticate their identity to one. After the initial verification, the user is cleared to access all their services and avoids using their credentials multiple times. 

SSO is beneficial in a business environment that increasingly depends on software as a service (SaaS), customer relationship management (CRM) software and other cloud-based solutions. In fact, 52% of IT professionals in North America reported using SSO for identity management. Using SSO enables an organization’s internal IT team to gain increased control over each user’s applications. The SSO technology verifies the user’s identity once and gives them the permissions they are authorized to have. 

How Does SSO Work? 

Single sign-on acts as a messenger, carrying credentials back and forth between an application and an SSO service acting as a database for user identities. It operates based on the trust established between an external service provider and an SSO service, called an identity provider. A trusted relationship with the SSO system is essential for the user to access any website or application.  

The identity provider and service provider exchange a certificate during the initial configuration to establish trust. The identity provider uses this certificate to sign any identification information it sends to the service provider. When the service provider recognizes the certificate, it verifies that the login credentials come from a trusted source. 

A few protocols are essential for SSO to work across websites. First is Open Authorization (OAuth) 2.0, a standard that enables third-party services or applications to access a user’s account information without sharing the user’s credentials. Another protocol is OpenID Connect, which builds on OAuth 2.0 to allow clients to confirm an end-user’s identity using an authorization server. 

When a user navigates to a service provider, the application or website creates an access token that remembers the user is verified. The access token contains bits of digital information from the user’s login credentials, like their username or email address. Each system passes the access token back and forth during the authentication process. The user’s browser or the SSO service’s server stores the access token for later so other applications can check with it whenever the user tries to log in. 

The SSO login process follows these steps: 

  1. The user navigates to an application or website known as the service provider. 
  2. The service provider sends an access token with the user’s credentials to the identity provider. 
  3. The identity provider investigates whether the user is already authenticated, in which case it will grant them access to the service provider. 
  4. If the user hasn’t yet logged in, the identity provider prompts them to provide their credentials saved in the identity provider. 
  5. The identity provider authenticates the user’s credentials and sends another access token to the service provider that verifies successful user authentication. 
  6. The service provider validates the token and authorizes user access. 

Types of SSO 

While each type of SSO service works, they also use different protocols and configurations. When your business is investigating SSO solutions, a few terms are helpful to know. Understanding the main types of SSO can help you decide which service is best for your enterprise’s needs. 

Here are the top four types of SSO and how they operate: 

1. Federated Identity Management 

Federated identity management (FIM) is a larger concept of which SSO is a part. FIM enables a relationship of trust between multiple parties. The parties in this relationship, which could be domains or identity management systems, can authenticate their identities across domains with a single sign-on. Organizations use FIM to allow users to access information across their domain and in third-party applications. 

Although SSO and FIM sound similar, there is a crucial difference. Federated identity management enables users to sign on to multiple applications across several domains, while standard SSO allows a single sign-on to the applications within a single domain.

When two domains share a relationship through FIM, users can verify their identity in one domain and access the other without needing to sign on again. FIM uses other protocols like Security Assertion Markup Language (SAML) to transmit information like user credentials and passwords. One party typically acts as an identity provider, storing and authenticating the user’s information for the service provider the user is trying to access. 

Access tokens carry vital information that helps users communicate with the SSO service. Each token must meet specific requirements to prove it is legitimate and comes from a trusted source. SAML is the primary access token standard, an open standard based on extensible markup language (XML). By using SAML, FIM ensures:

  • Convenience: SAML is a way of encoding access tokens from text into machine language and exchanging their data across domains. This technology allows information to be sent over a web browser to establish a token’s legitimacy — and, by extension, a user’s identity. SAML is the technology that enables user authentication, making SSO possible.
  • Authentication: A SAML-based SSO service sends access tokens between the user, the service provider and the identity provider. When the service provider requests user authentication, the identity provider sends a SAML assertion. This message provides the essential information for verifying the user’s authenticity. 
  • Security: Implementing SAML also increases security. Since the identity provider stores all the user’s information, it frees the service provider from needing to do so. 

2. Windows Integrated Authentication

Windows Integrated Authentication is an internet information services authentication protocol from Microsoft that lets users log into an application using their Windows credentials. This type of SSO doesn’t send user credentials in the request for authentication, protecting sensitive passwords. Windows Integrated Authentication only works for businesses using Windows. 

In Windows Integrated Authentication, authentication attempts usually go through the Kerberos protocol, an authentication protocol that enables users to authenticate themselves to the service provider. Kerberos uses a third party called the Key Distribution Center (KDC) and secret-key cryptography to verify the user’s identity. 

The KDC performs two functions in a Kerberos system — it authenticates the user and grants tickets, which contain all the necessary information for identifying the user and protecting information from cyberattacks. The KDC is made up of a database, an authentication server (AS) and a ticket-granting server (TGS). 

In a Kerberos-based SSO configuration, the user initiates a request for authentication using the client, a host on a Kerberos network that represents the user, which starts the service request. The AS examines the database for the client’s information and the availability of the TGS. Once the AS verifies both entities, it generates secret keys to begin the authentication process. Once Windows Integrated Authentication verifies the information, the user gains access to their websites and applications within the network. 

3. Client Certificate Authentication

Client certificate authentication exchanges certificates between the user and server to verify the user’s identity. While most forms of SSO require the user to input a password into the server, client certificate authentication uses certificates instead. These certificates must contain information like the client name, certificate expiration date and a trusted certificate authority’s signature. 

A smart card is a non-traditional form of SSO that utilizes hardware to perform client certificate authentication. Smart cards are physical microchips that allow user authentication by generating and storing encrypted keys and the user’s credentials.

An organization must grant each user a unique smart card. To operate a smart card, the user inserts it into the smart card reader in their computer. Then the computer asks for the user’s personal identification number (PIN) and verifies the user’s credentials. Once the user authenticates their identity, they will not have to sign in again to use the website or application. 

Smart cards are highly secure because they use the user’s PIN and other cryptographic keys to initiate authentication. It is difficult for a cyber attacker to access or modify the information a smart card stores because of the card’s construction. However, a user must physically carry their smart card, meaning they could lose it. Users can also only use their smart card on a computer with a smart card reader.  

Benefits of SSO 

As more organizations become aware of the threat of cyberattacks, authenticating each user has become more of a priority for increasing security and preventing information compromise. SSO provides organizations with several advantages when it comes to maintaining data security. Consider the top benefits of using SSO in your enterprise: 

1. Streamline Password Management 

SSO enables users to create and remember a single password for multiple applications and websites instead of making several passwords for all their accounts. When users only have to generate one password, they are free to create stronger passwords that are more immune to compromise. Using SSO also eliminates password fatigue, which is when users repeat passwords to make it easier to remember them. 

2. Simplify Logins 

SSO streamlines user authentication and logins across every application within the SSO system. With single sign-on, users can enter their passwords or credentials once and avoid reentering them multiple times. 

System administrators can also use SSO to enable easier multi-factor authentication (MFA). With MFA, a system uses multiple identity factors to verify a user’s identity, like a username, a password and a code sent to a smartphone number. An organization using SSO can require MFA at a single point to simplify the login process. Requiring multiple proofs of identity makes the system more secure than a password alone. 

3. Reduce Difficulties for IT Help Desks 

Your organization’s IT help desk handles various issues to ensure user information is protected. When users forget passwords or experience a compromise with their credentials, they contact the help desk for password recovery and reset. Because SSO reduces the number of passwords each user must manage, it cuts down on the time your internal teams spend on password recovery, giving them more time to work on more valuable tasks. 

Security Challenges 

Although SSO offers numerous benefits, it also presents a few challenges for organizations to manage. Consider some of the obstacles that organizations using SSO might experience: 

1. Enterprise Vulnerability 

An SSO system reduces the number of passwords used across a domain and limits potential weak spots for a cyberattack. However, it can also present its own risk to security. Since a user’s credentials grant them access to every website, application and server in the SSO system, anyone with the credentials can potentially access all of the information associated with the user. If an attacker gains access to a user’s SSO credentials, they can have control over all their applications. 

Using MFA is one strategy for combatting attacks on an SSO system. When a network requires users to input multiple forms of identification, it reduces the chance of an attacker gaining access to secure information. 

2. Interconnected System 

An SSO system is interconnected. Depending on the system’s protocol and configuration, a single login could grant access to websites and applications across multiple domains. If the user loses availability into the system, they are locked out of the entire network of applications. While recovering user credentials for an SSO system might be less time-consuming than resetting multiple passwords after a compromise, it is still tedious. 

3. Levels of Security 

Different applications and websites may require different levels of security. For instance, the healthcare industry requires robust security for medical records to comply with patient confidentiality laws. Although SSO is a highly secure way to manage passwords and applications, some enterprises might want additional protection for specific accounts. Many organizations use MFA or other identity management solutions to combat this issue. 

SSO With Optimal IdM 

At Optimal IdM, we believe SSO should be flexible, cost-effective and efficient to give you the security you need for your business. Optimal IdM offers custom on-premise and web SSO login services to help small and enterprise businesses mitigate security risks and manage compliance. We can adapt our on-premises and cloud-based SSO solutions to suit your needs, however complex.  

As Optimal IdM’s comprehensive SSO solution, the OptimalCloud can be customized to meet your business’s needs. Users can access all their applications on-premise or in the cloud with a single click. The OptimalCloud also provides adaptive multi-factor authentication to authenticate users, establish permissions and manage access controls with even greater security. 

Choose SSO Services From Optimal IdM

Single sign-on is a robust authentication solution for small and enterprise businesses alike. SSO benefits users by preventing password fatigue and streamlining password management. An SSO solution also simplifies the login process and saves users and IT departments time. 

The OptimalCloud from Optimal IdM provides businesses with an effective and customized authentication solution. With 24/7/365 expert service from Optimal IdM, using the OptimalCloud can reduce your business’s management and personnel costs. Contact the Optimal IdM team to learn more about why our SSO solution is your best choice for single sign-on authentication. 


  • The database in which all of your organization’s sensitive identity data is stored.
  • A digital ledger in which digital transactions are recorded chronologically and publicly.
  • Securely managing customer identity and profile data, and controlling customer access to applications and services.
  • The means of linking a person's electronic identity and attributes, stored across multiple distinct identity management systems.
  • A legal framework that sets guidelines for the collection and processing of personal information of individuals within the EU.
  • The policy-based centralized orchestration of user identity management and access control.
  • An authentication infrastructure that is built, hosted and managed by a third-party service provider.
  • A security system that requires more than one method of authentication from independent categories of credentials to verify the user's identity for a login or other transaction.
  • A global provider of innovative and affordable identity access management solutions. 
  • Managing and auditing account and data access by privileged users.
  • Tools and technologies for controlling user access to critical information within an organization.
  • An authentication process that allows a user to access multiple applications with one set of login credentials.

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