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Physical Contact in Ad-Hoc Wireless Network. Nie Pin 27.10.2006. Agenda. Introduction Assumptions on Ad-Hoc Wireless Network during the First Connect Constraints on mobile devices Attack Models Principles of Physical Contact Out-Of-Band (OOB) solutions Evaluation Conclusion. - PowerPoint PPT Presentation
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Physical Contact in Ad-Hoc Wireless Network
Nie Pin
27.10.2006
Agenda• Introduction• Assumptions on Ad-Hoc Wireless Network
during the First Connect • Constraints on mobile devices• Attack Models• Principles of Physical Contact• Out-Of-Band (OOB) solutions• Evaluation• Conclusion
Introduction• First Connect
– Initial setup of a security association among two or more devices for subsequent secure communication. Typical case: pairing of two devices, agreement signing between two parties.
• Physical Contact– Negotiating and exchanging process within a limited scope,
between two parties. (OOB)– Basic perceivability of the surroundings (users’ role)
• Out of Band (OOB)– A separate communicating band (auxiliary channel) other than
the one used for the subsequent communications, for exchanging security parameters (e.g. transmitting authentication data) or control information
Assumptions• Direct talk
– One-to-One communication style
• Demonstrative Identification (DI)– Authentication and confirmation– Limit the control range, reduce interferences
• No trusted third party– No valid assertion, token, rumor and recommendation
• No previous context– No history and experience
• Security Transient Association– Not necessary, but likely in practice, better to include
Constraints• User Interface
– Input• Keypad, handwriting, microphone, camera, biometric
detectors
– Output• Sticker (i.e. label), LED, beeper, LCD display
• Computing Power and Memory– Weak CPU (Intel PXA255 400MHz, bus 200MHz)– Little memory (HP iPAQ Pocket PC 2215 – 96MB,
Nokia 6822 – 3.5MB internal memory)
• Battery Consumption– Limited on electrical power (Nokia N95 – Talk
time:2.5-3.5 hours, PDA – Talk time:4-6 hours)
Attack Models• Active Attacks
– Denial-of-Service (DoS) attack• Block the target by flooding it with numerous requests• Considering the battery limit, it turns to be sleep deprivation
torture.
– Interference attack• Create too much strong noises to disable the detection at the
receiver’s side
– Man-in-the-middle (MITM) attack• Modifying data streams, inserting and deleting (break the
integration)• Playback of data, e.g. reflection attack and replay attack.
• Passive Attacks– Eavesdropping, a step for further attacking
Principles of Physical Contact• Bootstrap
– Imprinting, what should be bound or exchanged for subsequent secure communication?
• Proximity Detection– Fulfill the DI requirement
• Presence Confirmation– Derive from DI– Capture intention and set location restriction
• Pre-authentication– Control Information or security factors exchange by using OOB
• Flexibility– The solution can be carried out in many forms or OOBs to fit the
constraints of different devices
Out-Of-Band (OOB) solutions• Authenticated Strings
– Use commitment schemes to exchange the commitment, containing the keys and a “hidden value”
– Strings/numeric Comparison or Passkey-based– User acknowledges the check values on both devices or input the value (a
shared secret) to the other devices– Human knowledge based
• Radio, Infrared and ultrasound– Special transmitter and receiver for the channel– Location limited channel (LLC): distance binding– Closest proximity assumption is the necessary condition
• Visual Channel– Camera needed, display (e.g. LCD or LED) needed– Computing intensive analyzing algorithms– Two examples: SiB and VIC (DH-IC)
• Audio Channel– L&C with the same basic idea as SiB
• Biometrics Channel– E.g. Grip pattern, fingerprint, voice spectrum…
Evaluation
• Advantages– Benefits
• Pre-authentication, DI, MitM attack prevention
– Flexibility• Unidirectional authentication and mutual authentication
• Disadvantages– Algorithms complexity
• E.g. image processing, light signals processing, distance measurement, Integrity verification…
– Extra assumptions or overhead on devices and environment
• Channel carrier (e.g. transmitter, receiver, detector or camera, LED)
Evaluation (2)
• Human knowledge / biometric based– Simple, but needs user operation (e.g. compare or
input) as the auxiliary authentication channel
• Radio, infrared and ultrasound– Fool prove– High requirement on distance measuring– Special modules needed on the devices
• Visual channel– Easy to use– Algorithm complex and computing intensive
Conclusion• Balancing game
– Tradeoff between usability (human involved degree) and complexity (algorithms simulate human perceivability, e.g. seeing, touching, feeling)
– Tradeoff between security and efficiency, execution time (e.g. integrity verification)
• Fitting specific situations (applications scope)– One way authentication for ad-hoc services in public
places• Lower the requirements on SP’s equipments (e.g.
SC=>Passkey, SiB=>VIC)– Mutual authentication for peer-to-peer
communications• Make full use of popular equipments or functions on mobile
devices (e.g. SC, SiB)
Acknowledgement• Thanks for the comments and suggestions from
Prof. K. Nyberg , Prof. N. Asokan, Jukka Valkonen and Vesa Vaskelainen
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