How does password protection work for MS Word ? Which encryption is utilized ? Please relevant documentation links for details.

Hi @Amit Purswani,

Thank you for posting your question to Microsoft Q&A Forum.

Password protection in Microsoft Word uses strong encryption to secure documents and their contents.

There is two types of passwords:

• Encryption to open/view: Requires a password to decrypt and display document content.
• Modification restriction: Uses a password to prevent editing, but this does not encrypt content and is relatively weak.

The specific encryption depends on the version of Microsoft Office used:

All these versions use Microsoft's Office Document Cryptography Specification ([MS‑OFFCRYPTO]) to manage keys, salts, and encryption settings.

Password protection encrypts your document so only those with the correct password can access it. The process includes:

1. Password Entry
   Set a password via File > Info > Protect Document > Encrypt with Password.
2. Key Derivation
   Word converts the password into a strong key using SHA‑1 or SHA‑2 hashing, salt, and thousands of iterations.
3. Encryption
   The key encrypts the document with AES (128- or 256-bit), typically in CBC mode.
4. Storage
   Metadata (salt, iterations, algorithm info) is stored in the file, but the key itself is never saved.
5. Decryption
   Opening the file requires the correct password to regenerate the key and decrypt the content.
6. Safety
   Lost passwords cannot be recovered unless an IT tool like DocRecrypt was set up beforehand.

In conclusion, Microsoft Word secures documents using strong AES encryption (128‑bit or 256‑bit). The encryption key is derived from the password through a robust process involving hashing (SHA‑1 or SHA‑2), salt, and multiple iterations, ensuring high security. While metadata such as salt and algorithm details is stored in the file, the actual key is never saved decryption only occurs when the correct password is provided. Note that simple modification protection without encryption does not offer real security.

Please refer to the following official Microsoft articles for more information:

Protect a Word document with a password - Microsoft Support

Encryption in Microsoft 365 | Microsoft Learn

I hope this information is helpful.

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.

I look forward to continuing the conversation.

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