Enterprise security requires a comprehensive approach for defense in depth. Effective immediately, Azure Search now supports encryption at rest for all incoming data indexed on or after January 24, 2018, in all regions and SKUs including shared (free) services. With this announcement, encryption now extends throughout the entire indexing pipeline – from connection, through transmission, and down to indexed data stored in Azure Search.
At query time, you can implement user-identity access controls that trim search results of documents that the requestor is not authorized to see. Enhancements to filters enable integration with third-party authentication providers, as well as integration with Azure Active Directory.
Encryption at rest, on by default
All indexing includes encryption on the backend automatically with no measurable impact on indexing workloads or size. This applies to newly indexed documents only. For existing content, you have to re-index to gain encryption. Encryption status of any given index is not visible in the portal, nor available through the API. However, if you indexed after January 24, 2018, data is already encrypted.
Managed by Microsoft
In the context of Azure Search, all aspects of encryption, decryption, and key management are internal. You cannot turn it on or off, manage or substitute your own keys, or view encryption settings in the portal or programmatically. Internally, encryption is based on Azure Storage Service Encryption, using 256-bit AES encryption, one of the strongest block ciphers available.
Source: Azure Blog Feed