Microsoft 365 Excel version 2108 Encryption Level/Standard used for Encrypting Files at Rest

Question

I am able to find information on how to encrypt or password protect an Microsoft 365 Excel file. I need specific information on what encryption level/standard is used on Microsoft 365 Excel files at rest when saved on my Windows 10 computer in a folder.

Answer 1

I found the answer in the following document:

https://docs.microsoft.com/en-us/deployoffice/security/cryptography-and-encryption-in-office

Although there are Office 2016 settings to change how encryption is performed, when you encrypt Open XML Format files (.docx, .xslx, .pptx, and so on) the default values — AES (Advanced Encryption Standard), 256-bit key length, SHA1, and CBC (cipher block chaining) — provide strong encryption and should be fine for most organizations. AES encryption is the strongest industry-standard algorithm that is available and was selected by the National Security Agency (NSA) to be used as the standard for the United States Government.

Answer 2

Hi ReeseVan:

Please refer to the documentation for more information on Encryption, I think encryption standards should be based on user choice：

Encryption in Microsoft 365 - Microsoft 365 Compliance | Microsoft Docs

More information for you to reference:Protection and security in Excel (microsoft.com)

Hope this will help you.

Tin

Answer 3

Thank you for the quick response. I did searches on the Microsoft sites and found these pages.

I'm looking for information from a Microsoft source that indicates the encryption algorithm (i.e. AES) and the bit key size (i.e. 256-bit) that is being used in the symmetric key encryption for Office 365 documents (i.e. excel) that are saved to your local drive. In other word what is built into the software.

When this option is selected:

File-level: This refers to the ability to lock down your Excel file by specifying a password so that users can’t open or modify it. You have two choices here:

• File encryption: When you choose this option, you specify a password and lock the Excel file. This prevents other users from opening the file. For more information, see Protect an Excel file.