Usable Security for Webmail and Single Sign-on

1. Usable Security for Webmail and Single Sign-on Kent Seamons & Scott Ruoti Computer Science Department Brigham Young University Internet Security Research Lab

2. BYU Computer Science • CS Department has 600+ undergraduates, 80 MS, 30 PhD • Focus on undergraduate research mentoring

3. Internet Security Research Lab (ISRL) • Established 2001 • Funding: DARPA, NSF, Industry • Alumni • 24 MS degrees and 1 PhD degree awarded • Placement: Microsoft, Google, IBM, DoD, Sandia, MIT Lincoln Labs, Lockheed-Martin, Blue Coat, Amazon, etc.

4. ISRL Research Projects • Automated Trust Negotiation • TrustBuilder – exchange attribute certificates as a basis for trust • Convenient Decentralized Authentication using Passwords • Simple Authentication for the Web (SAW) • Luau • Easy, Secure Data Sharing in the Cloud • Private Webmail (Pwm) • Private Facebook Chat (PFC) • Key Escrow (Kiwi) • Privacy • TLS proxies – how to detect and distinguish from TLS MITM attacks • Usable Security

5. Users and Security • Users want to get their work done • They will sidestep security if it is inconvenient

6. Usable Security • A significant new research area in the last 10-15 years • Seminal papers • Why Johnny Can’t Encrypt (Whitten and Tygar, 1999) • Users are not the Enemy (Adams and Sasse, 1999) • Research venues with latest research • Symposium on Usability, Privacy, and Security (SOUPS) • ACM Conference on Human Factors in Computing Systems (CHI)

7. Why Johnny Can’t Encrypt • Usability study of PGP 5.0 • Political campaign scenario • Twelve users were given the software to configure • Users completed a series of tasks

8. Why Johnny Can’t Encrypt Results • Complete failure that served as a wakeup call to the community • Only four users (33%) were able to correctly send out the encrypted, signed email • Seven users encrypted emails with their own public keys • Another user generated new key pairs for all the other users and tried to encrypt email with those keys • Three users (25%) accidentally emailed the secret message to the other team members without encryption • Lots of challenges with key management

9. Usable Security Research Examples • Johnny 2 (SOUPS 2005) • Applied automatic key management to S/MIME email • A usability study and critique of two password managers (Usenix Security 2006) • Major usability issues discovered • Usability issues led to insecurity • Most significant problems arose from poor mental models • Social Phishing (CACM 2007) • User study that launched real phishing attack against Indiana University students using social network contact information (71% success rate)

10. Usable Security Research Examples • What makes users refuse web single sign-on? An empirical investigation of OpenID (SOUPS 2011) • Identified challenges and concerns users face when using OpenID • Many users had incorrect mental model of how the system worked (71%) • Identified changes in the login flow that improves user acceptance • Helping Johnny 2.0 Encrypt his Facebook conversations (SOUPS 2012) • Automatic key management and encryption • Hypothesized that users may not trust transparent encryption

11. Research Methods • Approaches from Human Computer Interaction (HCI) • Surveys • Likert Scale questions • Laboratory usability studies • Task-based • Difficult to draw conclusions from trust decisions in a laboratory environment • Amazon Mechanical Turks • Cost effective way for large-scale user studies • Ethical and privacy issues • Academic user studies need university review board approval

12. Metrics - System Usability Scale • System Usability Scale (SUS) [Brook 1996] • Ten questions using 5 point Likert Scale • Alternate negative and positive • Calculation that provides a single number for usability • Bangor compared scores for hundreds of systems

13. SUS Questions • I think that I would like to use this product frequently. • I found the product unnecessarily complex. • I thought the product was easy to use. • I think that I would need the support of a technical person to be able to use this product. • I found the various functions in the product were well integrated. • I thought there was too much inconsistency in this product. • I imagine that most people would learn to use this product very quickly. • I found the product very awkward to use. • I felt very confident using the product. • I needed to learn a lot of things before I could get going with this product.

14. Usable Security for Single Sign-On

15. Single Sign-on Who do we trust? The Internet Password

16. Simple Authentication for the Web • How can web sites offload user authentication all by themselves? • Already doing it as a secondary means of user authentication • SAW’s approach • Improve the security and convenience of email-based password resets • Use as primary authentication mechanism

17. How SAW Works User Web Site • Step 1: • The user submits her email address • Step 2: • If her address is authorized, a random secret is generated and split into two shares • Step 3: • The user returns both tokens • Manually: By clicking a link in the email • Automatically: Using the SAW toolbar • Tokens are: • Short-lived • Single-use • From: SAW_TokenGenerator@securecomm.org To: student@some.edu Subject: [SAW-https://securecomm.org/login] ATemail=2fe32... Click on the link below ONLY if you recently initiated a • request to log in to https://securecomm.org/login: https://securecomm.org/login?ATemail=2fe322492847eb5dea... I’m Alice User’s Email Provider

18. Benefits • Unilateral deployment by web sites • No specialized third party • No client-side software • Reuse existing users identifiers and authenticators external to the web site • Acceptable risk for services that rely on email-based password resets • Advanced features • Delegation and revocation through email forwarding rules • Client-side auditing

19. The Chicken and the Egg • How do users authenticate to identity providers when they cannot directly communicate? • Giving relying parties the plaintext password is not desirable • Allowing an encrypted tunnel invites misuse and requires IP-level connectivity • Forwarding several small messages of known composition offers a good compromise User (U) Wireless Access Point (RP) Identity Provider (IDP) Msg ID: Alice PW: Peek-a-boo

20. Luau– High Level Idea • Use a strong password protocol to establish a mutually authenticated session key between user and her identity provider • Use that key to facilitate a SAW token distribution • Unify Web and wireless authentication Secure Remote Password (SRP) User (U) Wireless Access Point (RP) Identity Provider (IDP)

21. Future Directions • Usability studies comparing SAW to Oauth, OpenID, and some recent proposals to replace passwords • Untrusted Input Problem: Password entry into web forms supplied by the server • We advocate a move to password entry into the browser chrome or O/S in order to thwart password phishing attacks • Train users to never enter credentials into a web page • Users will still be vulnerable to social engineering • If phishing attacks are thwarted, attackers will focus on the end points • Usable solutions to key logging

22. Confused Johnny: Usable Security for Webmail

23. Confused Johnny • E-mail encryption for the masses • We developed a system maximizing usability • Made everything transparent • Johnny became confused • Designed another system with manual encryption • This helped Johnny gain clarity

24. Encrypted E-mail • Exists, but largely goes unused • S/MIME, PGP • Tools available • “Why Johnny can't encrypt: A usability evaluation of PGP 5.0” • Whitten and Tygar, 8th USENIX Security Symposium (1999) • Later research confirmed findings • What can be done?

25. Usability Issues • Users resist change • Users are using webmail • If security is difficult users will forgo it • Key management is confusing • Hierarchical, web-of-trust • Recipient must already have key • Chicken and egg problem • Cryptography is complicated • Unclear which properties are provided • Unclear which properties are needed

26. Private Webmail (Pwm) • Pronounced “Poem” • Adds end-to-end encryption to existing webmail systems • Gmail, Hotmail, Yahoo! Mail • Runs on all modern browsers • Designed to maximize usability • Provide good-enough security • Improvement for those already sending sensitive e-mail

27. Security Overlay • Security overlay • Integrates tightly with existing webmail systems • Users do not need to learnyet-another-system • Tightly integrates with existing systems • Replaces small portions of the interface • Displayed using iFrames • Functionally transparent • Low barrier to adoption • Visually distinctive • Easy to identify

28. Usability Fixes • Users resist change • Focus on bootstrapping first-time users • Helpful instructions in e-mail • Bookmarklet-based installation • Key management is confusing • Key escrow based on IBE • Simple Authentication for the Web (EBIA) • No user interaction required • Cryptography is complicated • Encryption is automatically handled by Pwm • Users never interact with ciphertext

29. Pwm: Walkthrough

30. Pwm: Walkthrough

31. Pwm: Walkthrough

32. Pwm: Walkthrough

33. Pwm: Walkthrough

34. Pwm User Studies • Two studies • First study measured usability of Pwm • Also evaluated bookmarklets for use during installation • Second study compared Pwm to Voltage Secure Mail Cloud • Voltage Secure Mail Cloud is an existing depot-based secure email system • Pwm was run using a browser extension • Evaluation • Pre- and post-survey questionnaire • Monitored participants actions for unrecognized mistakes • Post-survey interviews

35. 76 71 63

36. SUS Score Comparison

37. Success? • Results are very promising • Very positive reception • Users indicated they wanted to begin using it • Not without problems • Small number sent e-mail without encryption • Participants were confused about security • Wanted to see more details • Unsure of who could read e-mails

38. Where to go from here? • Simple solutions was to fix UI issues • One student (Nathan Kim) had a different idea • Manual encryption • Decoupled interface • Mocked up these ideas • Message Protector (MP) • Simple Interface • Direct handling of ciphertext • Implied key management

39. MP: Walkthrough

40. MP: Walkthrough

41. MP: Walkthrough

42. MP: Walkthrough

43. First MP User Study • Evaluated MP using SUS • Compared against Encipher.it • Bookmarklet-based encryption system • Works in Gmail and Facebook • Evaluation • Pre- and post-survey questionnaire • Monitored participants actions for unrecognized mistakes • Post-survey interviews • The system usability scale • Evaluated comprehension • Survey included questions about comprehension • How to use the system • Who could read messages

44. 61 72

45. Second MP User Study • Surprising usability results • Participants had a positive reaction to seeing ciphertext • Similar SUS score to MP • Ran a second study comparing MP to Pwm • Modeled after the first MP study

46. 76 74

47. SUS Score Comparison

48. Other results • MP improved users comprehension • Clearly understood how to use system • Clearly understood who could read messages • Usability scores nearly identical to Pwm • Participants preferred manual encryption of MP • Participants preferred tight integration of Pwm

49. Study limitations • MP studies ignore bootstrapping new users • Studies assumed software pre-installed • Bootstrapping is a key component of Pwm’s design • Not fully representative of overall usability • Short-term studies • SUS question unclear • “I think that I would like to use this system frequently.” • Participants ranked low even when enthusiastic about the system • Relevant to security studies

50. Review • Pwm was a success • Participants largely succeeded at using encrypted e-mail • Participants had high praise for Pwm • Succeeding in being easy for new users • Pwm wasn’t perfect • Security was too transparent • Caused users to be confused and make mistakes • Mocked up a system using manual encryption • Users enjoyed manual encryption • Wished it was tightly integrated with the browser • A combination of approaches is needed to solve the problem