Anonymous Techniques for Securing Mobile Ad hoc NETworks (MANETs)

1. Anonymous Techniques for Securing Mobile Ad hoc NETworks (MANETs) Oscar Manso Helena Rifà

2. Network Anonymity Subject Anonymity Message Unlinkability Undetectability Dummy data Pseudonymity Mix router Burst communic. Trapdoor functions Mixed network Solutions for MANET Frequency Hopping Anonymous multicast Location-based Anonymity Issues on MANETs

3. 1.1 Pseudonymity • A pseudonym is an identifier of a subject other than one of the subject’s real names. • Pseudonymity is the use of pseudonyms as identifiers. • Ongoing use of the same pseudonym: • Allows the holder to establish a reputation (unless used by adversaries to impersonate the user) • Reduces the anonymity of the user (unless used by himself to misinform the adversaries). • Anonymity is stronger the less is known about the linking to a subject.

4. 1.2 Location-based identification • Addressing is referred to a location area • Broader area addressed →Greater anonymity • Receiver should provide proof of location to sender • Efficient routing mechanisms can be envisioned • Useful in specific settings • Emergency Rescue, Traffic, Military, etc..

5. 1.3 Trapdoor Functions • Trapdoor functions are one-way functions such as: • y=ƒ(x) is easy to compute • Given y is computationally infeasible to compute x Given trapdoor information, then it becomes feasible to find x for any given y such that ƒ(x)=y • Receiver anonymous identification can be achieved by: • Trapdoor function shared among sender and receiver • Trapdoor information only kept by receiver • Receiver can prove sender its ability to retrieve x value.

6. 2. Message unlinkability • Mix Router • Mix Network • Anonymous multicast

7. 2.1 Mix Router Two models: • Pool Mix • Continuous Mix

8. 2.2 Mix Network Two models: • Cascades • Free Mix Nets

9. 2.3 Anonymous Multicast Two models: • Onion Routing • Free Routes

10. 3. Undetectability The property of not being able to distinguish whether an object exists. • Aimed towards passive adversaries. • Techniques: • Dummy data • Frequency hopping • Burst communication

11. 3.1 Dummy data Introduction of fake messages in order to increase anonymity set. • Objective: Minimize amount of dummy data • When? Low traffic. • Preferably at random intervals of time • From where? Anywhere. • Most effective from destination. • Where to? • Inexistent location, cyclic path or faked routes

12. 3.2 Burst Communication Communication in very short bursts, so as to minimize the probability the adversary is monitoring • Low bandwidth • High latency

13. 3.3 Frequency hopping Transmission frequency change at time intervals according to shared key. • Poor at hiding the fact that communication is taking place • Direct Sequence Spread Spectrum (DSSS) transforms a high-power low-bandwidth signal into a high-bandwidth low-power signal • More difficult to detect because signal has to be extracted from noise

14. Conclusion Main issues: • Anonymous identification • Key Setup • Anonymous Routing mechanisms • Mutual anonymous authentication • Multiple path • Efficiency • Minimization of asymmetric key computations • Minimization of dummy messages • Security • Resistance to attacks (passive and active)