Encryption question... can still open files on different computer after encrypting


i'm new to file encryption. I tried it earlier, and i'm a bit confused. this is what i did:

I encrypted an excel file, and send it along with my outlook email. The recipient was able to open it just fine on a different computer. i didn't provide him with public key. why is this happening? isn't the recipient NOT supposed to be able to open the attachment because i didn't sent him any public key?? 

I then access my computer running win7(comp1) from a different computer running xp(comp2) using UNC path(shared folder). I copy the encrypted excel file from comp1 to comp2, and I could opened it just fine in comp2. isn't this supposed NOT to happen? 




Hello, Tom

File encryption is a transparent layer between your storage media and programs that automatically handle encrypting and decrypting a file/folder that is set to be encrypted. When a program access an encrypted file, it will be decrypted automatically (if Windows has the key) so that the program can read the data.

If you move a file around using Windows Explorer, the encryption will persist, if you open your file in Notepad for example, then choose Save As and specify another location, the new file will not be encrypted.

The only way the new file would be encrypted is if you encrypted the folder that the new file was saved to.

To reiterate, when you tell Outlook to attach a file to an email, the following happens:

Outlook tells Windows, I want to open “secret.txt”
Windows looks for secret.txt and see’s that it is encrypted.
Windows checks if it has the key to decrypt the file.
If Windows does NOT have the key, Windows tells Outlook “No”
If Windows DOES have the key, it decrypts the file and gives it to Outlook.

As a result, Outlook has no idea that the file is encrypted and sends it the same way it received the file, unencrypted.

Microsoft Answers Support Engineer
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Question Info

Last updated March 23, 2021 Views 3,628 Applies to: