Update 5/23/2023:
I reached out to the Product team to see if I can get more information on the key rotation frequency for PMK.
They confirmed that- no mention of it in the public documentation is intentional.
There are no plans to share this information publicly. It is a "security by obscurity" scenario. If it is a requirement for customers to have control on the rotation frequency, their recommendation is to use Customer Managed Keys. I hope that helps.
5/18/2023 (Summary from the comment above):
Unfortunately, the exact frequency of key rotation for PMKs in Azure cannot be publicly disclosed.
There is no mention of it in any public documentation.
However, it is worth noting that Azure offers several options for storing and managing your keys in the cloud, including Azure Key Vault, which allows you to configure key rotation policies for customer-managed keys. You can set a rotation policy to automatically generate a new key version at a specified frequency.
The rotation frequency for DEKs in Azure Disk Encryption can be determined by the user/administrator based on their specific requirements. Our recommendation is to rotate encryption keys at least every two years to meet cryptographic best practices.
Reference documentation: https://learn.microsoft.com/en-us/azure/virtual-machines/disk-encryption#about-encryption-key-management
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