Windows Encryption File System (EFS)
Tech Briefing
July 18th 2008
http://www.stanford.edu/services/efs
STANFORD UNIVERSITY • INFORMATION TECHNOLOGY SERVICES
Agenda
Stanford Users
• What is EFS
• What does it Protect
• Is this for me?
• Features
• Data Recovery Agent
• Getting Started
• Demo - How to Encrypt
• Demo – How to backup Key
IT Support Staff
• How to setup Data Recovery Agent
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What is Encrypting File System (EFS)
The Microsoft Windows Encrypting File System (EFS)
is feature built into the file system of the Windows XP
and Windows Vista operating systems. It lets you
encrypt designated files on a local computer so that no
other user can access your data. When a file is
encrypted, EFS automatically decrypts the file for use
and re-encrypts the file when it is saved.
EFS is particularly useful for protecting data on a
computer that might be physically stolen, such as a
laptop.
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What It Protects
 EFS protects files you designated if your computer is
lost or stolen.
 If someone tries to break in or has access into your
system to retrieve files, they will not be able to open
the file even if they can see that it exists (as long as
they do not have your SUNet ID and password).
 Files copied to a Web folder using WebDAV are kept
encrypted.
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What It Doesn’t Protect or Prevent
 It does NOT provide encryption to files that are:
• Sent via email
• Kept on a separate flash drive/thumb drive/USB
drive/floppy disk
• Moved over the network via shared folders (CIFS/AFS)
• System and page file
• Compress Files
• Files moved into folder set to encrypt all files
• Files form being deleted
 When you are about to move an encrypted file, Windows will
warn you that you will lose your EFS encryption. Keep in mind
that whenever you move a file off of your computer, it is
probably no longer protected by EFS.
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Is this for me?
 Reasons for using EFS
• Want to secure files on your computer incase it is stolen or lost
• You work with or store restricted data on your local computer
• You travel and need to work with restricted data
 Requirements
Windows XP Professional
Windows Vista Business, Enterprise or Ultimate
Computer is a member if University Windows Infrastructure (AD)
Users is logged on to the computer with their SUNet ID (WIN
Domain), local computer or child domain accounts will NOT work
• Hard drive is formatted with NTFS
•
•
•
•
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Features
 Microsoft Windows Encrypting File System (EFS)
• Transparent encryption done at the file-system level
• If a folder is marked, every file created or moved into it will be
encrypted
• File encryption keys can be archived (USB Flash Drive, File server)
• There is no “back door”
• Keys are protected with the users password on the computer
• Data Recovery Agent to allow for recovery of files if user’s key is
lost

Future Features
 Additional Users can be added to a file
 Group Policy to Auto Encrypt “My Documents” Folder
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Data Recovery Options
Once a file is encrypted only the users private key can
access the file. Should this key get lost the data will be
inaccessible. Options to protect the data include:
 User copies key to USB flash drive and store
separately from computer
 Configure Data Recover Agent (DRA)
• Domain Wide DRA
• Local/Departmental DRA
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Data Recovery Agent (DRA)
These data recovery agents (DRAs) are a separate set of
issued recovery certificates with public and private keys
that can be used to recover files.
Recommendation for DRAs
• Local Systems Administrators
• Separate flash drive (Iron Key) stored in secure location (safe)
Requirements for Recovery
• Admin will need read access to files at time of recovery
• Password for the DRA Private Key
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Getting Starting For End Users
 Open a HelpSU Request
 Once you have approval from your Local Support
Staff that they have setup the DRA you can then
choose directories to start encrypting.
 Copy your Key to a External USB Drive
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Demo 1
How To Encrypt Files
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Demo 2
How to back-up Your Keys
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Storing User Keys
 Export and then Delete Key on local computer
 External USB Flash Drive
• NOT stored with your computer or in laptop bag
• Encrypted (optional)What
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Known Issues
 DCOM Required
1. Start Registry Editor.
2. Locate the following path:
HKEY_LOCAL_MACHINE\Software\Microsoft\OLE
3. Change the EnableDCOM string value to Y.
4. Restart the operating system for the changes to take effect.
Note: There is a BigFix fixlet to re-enable DCOM
 Vista and Symantec Bug – Patch available on ESS
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Demo 3
How to Setup DRA
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Questions and Answers
 Extra Info for users and admins
• Stanford Data Classification
http://www.stanford.edu/group/security/securecomputing/datacl
ass_chart.html
• Windows Desktop File Encryption and EFS
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