How Do Tor Users Interact With Onion Services? Philipp Winter, Annie - - PowerPoint PPT Presentation

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How Do Tor Users Interact With Onion Services? Philipp Winter, Annie - - PowerPoint PPT Presentation

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How Do Tor Users Interact With Onion Services? Philipp Winter, Annie Edmundson , Laura Roberts, Agnieszka Dutkowska-Zuk, Marshini Chetty, Nick Feamster USENIX Security Symposium 15 August 2018 1 Tor is a Decentralized Anonymity Network The

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How Do Tor Users Interact With Onion Services?

Philipp Winter, Annie Edmundson, Laura Roberts, Agnieszka Dutkowska-Zuk, Marshini Chetty, Nick Feamster

USENIX Security Symposium 15 August 2018

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SLIDE 2

Tor is a Decentralized Anonymity Network

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The Tor network

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SLIDE 3

Onion Services Provide Server Anonymity

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The Tor network

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SLIDE 4

How Do Users Interact with Onion Services?

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  • What are users’ mental models of onion services?
  • How do users use and manage onion services?
  • What are the challenges of using onion services?
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SLIDE 5

Main Findings

Despite extra security and privacy properties of onion services, many users are confronted with usability issues

  • Discovering the existence of onion services
  • Managing and remembering onion domains
  • Susceptibility to phishing attacks

We can learn from the issues users have encountered to implement design improvements

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Overview

1. Onion Services Background + Features 2. Methods 3. Results

a. Onion Sites Discovery b. Vanity Domains c. Verifying Onion Sites

4. Future Directions & Conclusions

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http://expyuzz4wqqyqhjn.onion

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http://expyuzz4wqqyqhjn.onion

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Special-use domain

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http://expyuzz4wqqyqhjn.onion

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Truncated, base 32-encoded hash over RSA public key

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http://expyuzz4wqqyqhjn.onion

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Not limited to HTTP(S)

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Onion Service UI is Designed to be Seamless

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Onion Service UI is Designed to be Seamless

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Onion Service UI is Designed to be Seamless

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SLIDE 14

Onion Service UI is Designed to be Seamless

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SLIDE 15

Onion Services are Self-authenticating

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3wcwjjnuvjyazeza.onion 3wcwjjnuvjyazeza

The Tor network

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Onion Services are Self-authenticating

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3wcwjjnuvjyazeza.onion 3wcwjjnuvjyazeza

The Tor network

Public key

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SLIDE 17

Onion Services are Self-authenticating

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3wcwjjnuvjyazeza.onion 3wcwjjnuvjyazeza

The Tor network

Public key

SHA-1

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SLIDE 18

Onion Services are End-to-end Encrypted

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3wcwjjnuvjyazeza

The Tor network

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SLIDE 19

Onion Services are End-to-end Encrypted

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3wcwjjnuvjyazeza

The Tor network

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SLIDE 20

Both Client and Server are Anonymous

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3wcwjjnuvjyazeza

The Tor network

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SLIDE 21

Both Client and Server are Anonymous

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3wcwjjnuvjyazeza

The Tor network

I talk to the client through relay R2 I talk to the onion service through relay R2 I have no idea who I’m talking to

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SLIDE 22

While onion services provide anonymity benefits, they are not perfect.

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  • Susceptible to traffic analysis attacks
  • Configuration errors
  • Usability issues
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SLIDE 23

Overview

  • 1. Onion Services Background + Features
  • 2. Methods
  • 3. Results
  • a. Onion Sites Discovery
  • b. Vanity Domains
  • c. Verifying Onion Sites
  • 4. Future Directions & Conclusions

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SLIDE 24

How Do Users Interact with Onion Services?

24

  • What are users’ mental models of onion services?
  • How do users use and manage onion services?
  • What are the challenges of using onion services?
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SLIDE 25

How Do Users Interact with Onion Services?

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Mixed-method user study

Interviews Survey DNS B Root Data

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SLIDE 26

How Do Users Interact with Onion Services?

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Mixed-method user study

Interviews

  • N=17
  • Diverse

backgrounds

  • Exploratory

Survey DNS B Root Data

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SLIDE 27

How Do Users Interact with Onion Services?

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Mixed-method user study

Interviews

  • N=17
  • Diverse

backgrounds

  • Exploratory

Survey

  • N=517
  • 49 questions (mix
  • f open-ended and

closed-ended)

  • 4 attention checks

DNS B Root Data

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SLIDE 28

How Do Users Interact with Onion Services?

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Mixed-method user study

Interviews

  • N=17
  • Diverse

backgrounds

  • Exploratory

Survey

  • N=517
  • 49 questions (mix
  • f open-ended and

closed-ended

  • 4 attention checks

DNS B Root Data

  • ~2 days of data
  • Filtered correctly

formatted .onion domains

  • 15,471 leaked
  • nion domains
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SLIDE 29

Overview

  • 1. Onion Services Background + Features
  • 2. Methods
  • 3. Results
  • a. Onion Sites Discovery
  • b. Vanity Domains
  • c. Verifying Onion Sites
  • 4. Future Directions & Conclusions

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Makeshift Solutions Ease Onion Discovery

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SLIDE 31

Makeshift Solutions Ease Onion Discovery

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SLIDE 32

Makeshift Solutions Ease Onion Discovery

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Makeshift Solutions Ease Onion Discovery

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I wasn't aware that onion site search engines exist. It's been near impossible for me to find them so far.

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Survey Respondent (S195)

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Onion Domain Management is Chaotic

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Onion Domain Management is Chaotic

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Onion Domains are Difficult to Remember

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Onion Domains are Difficult to Remember

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Meaningful prefixes appear to make remembering easier

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Phonetic pronunciation plays a large part in how I remember onions.

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Survey Respondent (S46)

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Vanity Onion Domains

propub3r6espa33w.onion nytimes3xbfgragh.onion facebookcorewwwi.onion protonirockerxow.onion

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SLIDE 44

Vanity Onion Domains

propub3r6espa33w.onion nytimes3xbfgragh.onion facebookcorewwwi.onion protonirockerxow.onion

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  • Generate onion domains

until hash resembles desired string

  • The good:

○ Hints at onion service content

  • The bad:

○ Breeds false sense of security ○ Economically unfair

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SLIDE 45

I only memorize the first part of the domain.

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Survey Respondent (S96)

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I understand vanity onion domains are a sign of the weakness of the hash algorithm used by Tor.

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Survey Respondent (S454)

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These people who created their onion name using scallion or other tools should notice that other people can make [the] same private key.

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Survey Respondent (S552)

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SLIDE 48

Onion Lookups Suggest Typos or Phishing

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hydraruzxpnew4af.onion hydraruzxpnew3af.onion

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SLIDE 49

Onion Lookups Suggest Typos or Phishing

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hydraruzxpnew4af.onion hydraruzxpnew3af.onion

529 occurrences in DNS dataset 2 occurrences in DNS dataset

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SLIDE 50

Onion Lookups Suggest Typos or Phishing

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hydraruzxpnew4af.onion hydraruzxpnew3af.onion

529 occurrences in DNS dataset 2 occurrences in DNS dataset Unique, correctly-formatted

  • nion domains

Jaro-Winkler similarity score Weight results by frequency

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SLIDE 51

Onion Lookups Suggest Typos or Phishing

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Onion Lookups Suggest Typos or Phishing

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Russian Market DuckDuckGo The Hidden Wiki

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Onion Sites are Hard to Verify as Authentic

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Onion Sites are Hard to Verify as Authentic

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Onion Sites are Hard to Verify as Authentic

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Summary of Findings

  • Discovering onion services is challenging because they

are private by default

  • Vanity domains are more memorable but provide a false

sense of security

  • Users are lacking a way to verify the authenticity of onion

domains

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SLIDE 57

Overview

  • 1. Onion Services Background + Features
  • 2. Methods
  • 3. Results
  • a. Onion Sites Discovery
  • b. Vanity Domains
  • c. Verifying Onion Sites
  • 4. Future Directions & Conclusions

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SLIDE 58

Making Onion Domains More Usable

  • Make it easier for site foo.com to announce its onion

service

  • Allow onion service operators to opt-in to publishing

mechanism

  • Have Tor Browser help with encrypted bookmarks
  • Better documentation and education

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SLIDE 59

Conclusion

Despite extra security and privacy properties of onion services, many users are confronted with usability issues

  • Susceptibility of onion services to phishing attacks
  • Discovering the existence of onion services
  • Managing and remembering onion domains

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SLIDE 60

Conclusion

Despite extra security and privacy properties of onion services, many users are confronted with usability issues

  • Susceptibility of onion services to phishing attacks
  • Discovering the existence of onion services
  • Managing and remembering onion domains

We can learn from the issues users have encountered to implement design improvements

  • Better discovery mechanisms
  • Better verification mechanisms

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Questions?

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More info at: https://nymity.ch/onion-services/ https://hci.princeton.edu https://citp.princeton.edu/ Sponsored by: