Microsoft Purview Information Protection moving to AES256-CBC mode for encryption of email and Office files

Microsoft has recently announced that Microsoft Purview Information Protection will be transitioning to Advanced Encryption Standard (AES) with 256-bit key length in Cipher Block Chaining mode (AES256-CBC) for encrypting emails and Office files by default. This change will take place in late August 2023 and is expected to complete by late September 2023. The current default encryption algorithm, AES128 in electronic codebook mode (AES128-ECB), will be replaced by AES256-CBC for files and emails. This change will affect Microsoft 365 Apps on Current Channel and Monthly-Enterprise Channel, SharePoint Online, Exchange Online, and Office 365 Message Encryption among other services. It is important for four specific groups of organizations to take action to update or opt-out of this change, which is outlined in more detail in Microsoft's Tech Community blog post and documentation. The post Microsoft Purview Information Protection moving to AES256-CBC mode for encryption of email and Office files provides more information on the impact of this change and the necessary preparation actions that organizations may need to take.