Windows has an encryption tool to prevent other users from opening your files but install a more robust third-party tool for greater privacy.
- Right-click the folder you want to lock, and select Properties.
- Press Advanced at the bottom of the General tab.
- Put a check in the box next to Encrypt contents to secure data.
- Select OK, and then OK again on the Properties window to save.
Windows will prompt you to back up your file encryption key to avoid permanently losing access to your encrypted files. You can follow those steps (keep reading) or ignore them.
5. Select Back up now (recommended) if you followed the notification to back it up.
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6. Start the Certificate Export Wizard by selecting Next on the first screen.
7. Keep the defaults selected, and then press Next again.
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8. Select the box next to Password to enable the password, and fill out the text fields below. Select Next.
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9. Choose where to save the PFX file, and give it a name.
10. Select Next to review the information you provided and select Finish to complete the export.
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11. Select OK on the successful export prompt. If you ever need to use this certificate, just open it from wherever you saved it in step 9, and follow the on-screen prompts.
How Encrypted Files Work on Windows 10
You should know how encrypted files behave in Windows to ensure this is the method you want to use.
Take this as an example: An encrypted folder exists on the root of the C drive of a computer with two users. John encrypts the folder and all the files inside it. He has complete control over the data.
Another user, Mark, logs in to his account, where he can do nearly everything John can:
- See file names
- Rename files
- Move and delete the folder and its files
- Add more files to the folder
However, because John encrypted the files in the folder, Mark can’t open them. Mark can, however, do essentially anything else.
Any files Mark adds to the encrypted folder are automatically encrypted, but now the permissions are reversed: Since Mark is the logged-in user, he can open the files he adds, but John can’t.
Source: https://www.lifewire.com/lock-folder-in-windows-10-5210654