1. CrowdShare
Secure Resource Sharing in Mobile Crowds
Stanislaus Stelle
CASED / TU Darmstadt
8th of March 2013 on Moosecon
Joined work with
Alexandra Dmitrienko | Ahmad-Reza Sadeghi | Elena Reshetova | Thomas Schneider | N. Asokan
1

2. Motivation
2

3. Motivation
Resource Sharing
3

4. Motivation
Resource Sharing
Collaborative work
4

5. Motivation
Resource Sharing
Collaborative work
Social Networks
5

6. Motivation
Resource Sharing
Collaborative work
Social Networks
Mobile
6

7. Depends on
Carrier
7

8. 4.6 billions without
Internet
8

9. 4.6 billions without
Internet
Focus on Internet
Availability
9

10. What can we
do about it
10

11. Existing Technology: Tethering
Participant
Participant
Access Point
11

12. Existing Technology: Tethering
Range
Participant
Participant
Access Point
12

13. Existing Technology: Tethering
Range
Password
Distribution
Password Participant
Participant
Access Point
Password
13

14. Solution: Multihop Resource
Sharing 14

15. How should
this work?
15

16. Mesh Network Routing: BATMAN
16

17. What about
security?
17

18. Link Security

19. Link Security Access Control

20. Anonymity
Link Security Access Control
20

21. Liability
Anonymity
Link Security Access Control
21

22. Implementation
for Android
Link Security – SSL/VPN
Anonymity – Registration with Certs.
Liability – Signed Resource Requests
Access Control – FoF Service

23. And what
about
liability?
23

24. Liability
Internet
Wants to tether Has Internet Connection
24

25. Liability
25

26. Liability
26

27. Liability
27

28. Bound to phone number Liability
Destination IP, Protocol, Port, Timestamp
28

29. Liability
29

30. Liability
30

31. Liability
31

32. Liability
32

33. Liability
33

34. Liability
34

35. And what
about
access
control?
35

36. Friend of Friend Service
Simple alternative
Fancy alternative
36

37. Simple alternative
register
37

38. Simple alternative
sync
38

39. Simple alternative
Transmit
Whitelists
39

40. Fancy alternative
40

41. Challenges
WiFi and 3G at the same time
WiFi in Ad-Hoc mode
Dynamic Access Control

42. WiFi and 3G at the same time
Android prohibits both to be activated
insmod /system/lib/modules/bcm4329
firmware_path=/system/vendor/firmware/fw_bcm4329.bin

43. WiFi in Ad-Hoc mode
No System option in Android
iwconfig eth0 channel 11 essid Mesh mode ad-hoc
ifconfig eth0 10.0.0.1 netmask 255.0.0.0 up

44. Dynamic Access Control
Friend of Friend Service
Liability Feature

45. Conclusion
1) Design of CrowdShare service for secure resource sharing
a. Allows arbitrary people to establish mesh and share resources
b. Enables users to decide what and with whom to share
c. Ensures anonymity, liability, confidentiality, authenticity
2) Implementation for Internet sharing on Android devices
a. Extends Serval
b. Enables internet sharing
c. Brings in a security layer
d. Addresses a number of technical challenges

46. T ha n
k y ou
Ques
ti ons?

47. Stanislaus Stelle
Freelancer
stas.stelle@gmail.com