In Q1 2017 Microsoft released the Pass Through Authentication (PTA) functionality as part of Azure AD connect. With the release of Azure Active Directory (Azure AD) Pass-through Authentication allowed for your users to sign in to both on-premises and cloud-based applications using the same passwords without the need to implement a Active Directory Federation Services (ADFS) environment.
With this options we now have the following authentication options available when setting up a hyrid identiy:
- Password hash synchronization (PHS) – https://docs.microsoft.com/en-us/azure/active-directory/hybrid/whatis-phs
- Pass-through authentication (PTA) – https://docs.microsoft.com/en-us/azure/active-directory/hybrid/how-to-connect-pta
- Federation (AD FS) – https://docs.microsoft.com/en-us/azure/active-directory/hybrid/whatis-fed