1. Private Facebook Chat
Chris Robison, Scott Ruoti, Tim van der Horst, Kent Seamons
Internet Security Research Lab
Computer Science Department
Brigham Young University
25 minute presentation – (20-22) leaving 3-5 minutes for questions

2. Motivation Instant messaging is growing*
1 billion IM users
200 million new users each year
47 million instant messages per day
53 messages per user per day
Instant messaging is moving to social networks
Facebook Chat has the largest user base
Facebook Chat is not secure
Transmission of messages over secure channel not guaranteed
Even more direct introduction. Prepare it. “The motivation for this work is…”
Example of stand-alone clients to social networks
*Source: statistics report ,

3. Research Outline What are users attitudes towards instant messaging?
Are they aware of security and privacy issues?
Private Facebook Chat (PFC)
Prototype for adding end-to-end encryption to Facebook Chat
Designed for usability and security
PFC usability study
Test the ability of users to correctly begin using PFC
Watch casual language.
Describe the grass roots adoption of PFC. See if they could use it easily and correctly. Current users, without training.

4. User Survey Preliminary survey to guide research 65 respondents
Distributed via word of mouth, and social networks
18 questions
Usage
Trust
Privacy

5. Usage Patterns Systems used Frequency Google Talk (67%)
Facebook Chat (50%)
Skype (41%)
Frequency
Half used it daily
Another quarter used it at least once a week.
Users could select more than one answer

6. User Trust Group 1: Felt safe using IM
Group 2: Never thought about security in IM
Group 3: Felt unsafe using IM
All sent sensitive information. 15% of Group 1 even sent highly sensitive information.

7. User Trust
Question: Are you more likely to send sensitive information to trusted friend or family member?
Question: Would you reply with sensitive information to trusted friend or family member?
While we might think we won’t send sensitive information, when it comes down to it we will.
Nearly ¾ willing to send sensitive information to family.
About ½ somewhat willing to reply to a request for sensitive information.

8. Question: I’m confident chat conversations are private.
User Privacy
Question: I’m confident chat conversations are private.
¼ think chat is private, while another ¼ don’t know.

9. Private Facebook Chat Adding end-to-end encryption to Facebook Chat
Protection from eavesdroppers
Protection from honest-but-curious Facebook
Designed for ease of use
Continues to make use of existing interface
Layers on security
Grass roots adoption model
No participation by Facebook required
Easy, fast installation

10. Threat Model Alice Network Facebook Bob HTTPS not on by default
May be used on one side and not the other
Network
Facebook
Bob

11. Security Overlays Adds end-to-end encryption to Facebook Chat
Window where secure interaction occurs
Positioned directly over original interface
Functionally equivalent, but visually distinctive
Secure content not accessible to Facebook
Facebook will show encrypted content. We show plaintext.

12. User Interaction Alice’s Screen Bob’s Screen
This series of slides shows screenshots of the interface. Use it to tell the story of how Alice chats securely with Bob for the first time.

13. User Interaction

14. User Interaction Alice’s Screen Bob’s Screen
This series of slides shows screenshots of the interface. Use it to tell the story of how Alice chats securely with Bob for the first time.

15. Implementation Security Key management Bookmarklets AES
Confidentiality, Integrity
Could add Forward secrecy
Key management
Traditionally difficult for users
Used key escrow
Identity based
Symmetric
Bookmarklets
Easy to setup and use
Requires no elevated permissions

16. Security Analysis Good enough security Passive attacks Key compromise
Focused on usability
Usually a tradeoff between security and usability
Passive attacks
Defeated by end-to-end encryption
Key compromise
Separation of duties
Short key periods
Impersonation
Facebook account compromised
Could use stronger authentication
Social Engineering
Convincing users to install malicious bookmarklets

17. Usability Study IRB-approved study 17 Facebook Chat users 5 tasks
8 from BYU
9 from a local software company
5 tasks
Installation
Sending and receiving secure messages
Ensuring the system was in use
Participants had no advance notice that the study would focus on security

18. Lessons Learned Bookmarklets are usable
15/17 (88%) were able to chat securely
9/17 (53%) were wary of adding Facebook application
Easy to tell when chat was secure
3/17 (18%) users accidentally sent sensitive information in the clear
Occurred because they forgot to first click the bookmarklet
Users found it desirable
13/17 (76%) said they would use it with friends/family if the system were available.
Be specific about numbers.
Be clear of limitation of bookmarklet vs. plug in

19. Conclusions User survey PFC Usability study
False sense of security permeates IM
Users already send sensitive information over IM
PFC
Adds end-to-end security to Facebook
Security overlays layer on security.
Usability study
Nearly all users successfully used
Bookmarklets easy to use
Key management has always been difficult

20. Future Work Ways to potentially increase security Webmail
Needs to preserve usability
Authentication
Prevent phishing and social engineering
Conditioned-safe ceremonies
Bookmarklet verification
Formal security analysis
Webmail
Other dominant form of internet-based communication
Conducted preliminary study with good results
Further usability studies
Long term study
Are bookmarklets better or worse than plug-ins?
Trust of initial message
Spear phishing problem turned on its head
Personalized greeting to motivate receiver to install the bookmarklet
Conditioned-safe ceremonies and a user study of an application to web authentication
C Karlof, JD Tygar, D Wagner - Proc. NDSS, cs.berkeley.edu

21. Questions