📖 What is Microsoft Entra ID Password Hash Synchronization (PHS)?
Microsoft Entra ID Password Hash Synchronization (PHS) is an authentication method that synchronizes a hash of the user's on-premises password hash to Microsoft Entra ID. This allows users to sign in to cloud services using their local credentials.
"Note that PHS is the simplest deployment model and is required to enable leaked credential detection in the cloud."
📚 Certification: Microsoft 365 Administrator (MS-102)
🔑 What are the Key Concepts of Microsoft Entra ID Password Hash Synchronization (PHS)?
- ▸ Utilizes a double-hashing process where a hash of the on-premises password hash is synchronized, ensuring the actual plaintext password never leaves the local environment.
- ▸ Requires the installation and configuration of Microsoft Entra Connect or Cloud Sync to facilitate the secure transfer of credential hashes from Active Directory.
- ▸ Provides the highest availability for cloud authentication because users can sign in even if the on-premises identity infrastructure is completely offline or unreachable.
- ▸ Serves as a mandatory prerequisite for Entra ID Protection's leaked credential detection, which identifies passwords exposed on the dark web via third-party sources.
🎯 How does Microsoft Entra ID Password Hash Synchronization (PHS) appear on the MS-102 Exam?
You may be asked to recommend the most simple and resilient authentication method for a small organization that wants to avoid maintaining complex on-premises infrastructure for cloud logins while ensuring high availability.
A scenario might describe a requirement to implement 'Leaked Credential Detection' as part of a Zero Trust security strategy; you must identify PHS as the necessary synchronization method to enable this feature.
Expect questions comparing PHS with Pass-through Authentication (PTA), specifically focusing on which method allows authentication to continue without interruption if the on-premises domain controllers are unavailable or offline.
❓ Frequently Asked Questions
Does PHS compromise security by storing passwords in the cloud?
No, because Microsoft does not store the password or the original hash. It stores a hash of the hash, making it computationally infeasible to reverse-engineer the original password from the cloud data.
Can PHS be used as a backup for other authentication methods?
Yes, PHS can be configured as a failover mechanism for Pass-through Authentication or Federation. If the primary on-premises authentication service fails, Entra ID can switch to PHS to prevent user lockout.