SECURE DEVICE ASSOCIATION:

TRENDS AND ISSUES

Presenter Gicheol Wang

Yasir Arfat Malkani, Dan Chalmers, and Ian Wakeman

presented by gcwang

Outline

Introduction

Problem

Challenges

Background

Summary and Future Directions for Research

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Introduction–Mobile Ad Hoc Environments

More and more devices every day Varying size and capabilities Varying connection methods (e.g. Cable, Bluetooth, etc) Varying user interface (rich, moderate and poor)

Spontaneous method of interaction Increasing Mobility in devices Use of wireless technology in some form

e.g. 802.11,Bluetooth, Infrared, Zigbee, Wibree, etc Frequent associations and disassociations

e.g. pairing of Bluetooth enable headset with mobile phone or MP3 player, pairing IR remote with laptop, etc.

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Problem

-------------------------Intended Communication

___________Actual Communication

Man-in-the-middle attacker

A B

E

SolutionEstablishing secure channel between the pairing devices

• Eavesdropping• Disclosure of sensitive information to 3rd Party

• Manipulation• Illegitimate analysis and modification of data• Can cause Denial-of-Service (DoS)• E can gain control over the device B

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Challenges

No prior context Devices lack prior knowledge of each other due to ad hoc

nature

No pre-shared secret key Traditional key exchange/agreement approaches

(e.g. Diffie- Hellman) are not secure against MiTM attack

Variations in device capabilities Communication channels User-interfaces Power and computational resources Sensing technology, etc.

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Attack Types in Device Association Model

Eavesdropping and MiTM attack Discussed in previous slides

Denial-of-Service (DoS) attack Prevent communication between wirelessly connected nodes Prevents pairing partners to establish a secure channel

Bidding-Down attack It is possible, where a list of choices to establish a secure

channel is available The goal is to fool (bid-down) the devices to use weaker security

than is possible

Compromised Devices Difficult to prevent at the protocol level Could suggest pairing with only the adversary’s device Could run a weak pairing protocol

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Background

Resurrecting Duckling Security Model Talking to Strangers Visual Out-of-Band Channels Audio Out-of-Band Channels Accelerometer-Based Approaches Radio-Signals Based Approaches Biometrics-Based Approaches Button Enabled Device Association (BEDA) Industry and Standardization Bodies

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Resurrecting Duckling Security Model

Exchange encryption key in plain-text form using a

physical medium, such as cable

No cryptography required

Cables are cumbersome

Not all the devices have similar physical interface

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Actual Communication

Inte

nded Com

municatio

n

Talking to Strangers

Extended Resurrecting Duckling security model Two-phase authentication

Use infrared as an out-of-band (OOB) channel

Susceptible to eavesdropping e.g. Two remotes and one projector

Rene Mayrhofer et al. Use laser [4, (2007)] and Ultrasound [5, (2007)]

Requires interface and/or additional hardware, such

as laser/ultrasound transceiver923年 4月 19日

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Visual Out-of-Band Channels Seeing-is-Believing (SiB) by McCune et al.

Use camera phones and bar codes to create visual OOB channel

Secure Device Pairing Based on Visual Channel by Saxena et al. Proposed an improvement to SiB through the use of LED

and short authenticated integrity checksums Not all devices are equipped with camera Might not be enough light at some places to scan bar

codes properly Not all devices have big enough displays to show 2D bar

codes In some situations, camera equipped devices cannot be

placed sufficiently near Camera-equipped devices are not allowed in security-

sensitive areas

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Audio Out-of-Band Channels Loud and Clear (L&C)

Use audio as OOB channel for human-assisted authentication Derive auditorially-robust, syntactically correct, but nonsensical

(MadLib) sentence from hash of a public key Compare the vocalized sentences

Human-Assisted Pure Audio Device Pairing (HAPADEP) Pairing two devices that have no common standard wireless channel

at the time of pairing Use audio to exchange both cryptographic material and protocol

messages

Not applicable to pairing scenarios where one of the devices does not have a display and/or a speaker (or microphone in case of HAPADEP)

Not suitable for hearing-impaired users Not feasible in noisy environments Places burden on user to compare the two Madlib sentences or

Melodies

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Accelerometer-Based Approaches

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Smart-its-Friend by Holmquist et al. Use common readings from the embedded accelerometers in

the devices Security has not been the major concern

Are You With ME by Lester et al. Use accelerometers’ data to show that a set of devices is being

carried by the same person Shake-Well-Before-Use by Mayrhofer et al.

Combine cryptographic primitives with accelerometer data analysis for secure device-to-device authentication

Require accelerometer in each device Large variety of devices can not be shaken together

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Radio-Signals Based Approaches Radio-Based approaches require no or minimal hardware and/or user

involvement Shake-Them-Up by Castelluccia et al.

Movement-based technique for pairing two resource-constrained devices, such as sensors.

Use the source indistinguishability property of radio signals

Susceptible to attack by an eavesdropper that exploits the differences in the base-band frequencies of the two radio sources

Amigo by Varshavsky et al. Utilize commonality of radio signals from locally available wireless access

points Extended Diffie-Hellman key exchange protocol with the addition of a key

verification stage

Not applicable in the scenarios where radio-date is not available

Hard to identify the intended device when many other devices surround it.

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Biometrics-Based Approaches

Biometrics are a common technique for identifying human beings

Feeling-is-Believing (FiB) by Buhan et al. Investigated grip pattern Proposed to generate a shared secret key from biometric data

using quantization and cryptanalysis Secure Ad-hoc Pairing with Biometrics (SAfE) by Buhan et al.

Keys are extracted from images during the pre-authentication phase

Both of the techniques are based on Balfanz et al. model

Logic and calculations to accurately recognize the biometric-patterns are a heavy burden on its applications

Issue regarding the accuracy of recognition techniques still need more research and improvement

Require biometrics reader in both of the devices

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Button Enabled Device Association (BEDA)

Transfer the short secret key from one device to the other using ‘button-presses’

Then, the short secret key is used to authenticate the public keys of the devices

There are four variants of BEDA Button-to-Button (B-to-B)

Involves the user simultaneously pressing buttons on both of the devices within certain random time-intervals

Each of these intervals are used to derive 3-bits of the short secret key Display-to-Button (D-to-B)

Emits visual signals by showing a blinking square on its screen. The user reacts to blinking square events by pressing the button on the

other device. Short-Vibration-to-Button (SV-to-B)

Transmits signals through short vibration events instead of blinking square Long-Vibration-to-Button (LV-to-B)

Signals are emitted through either the start or the end of a long vibration

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Industry and Standardization Bodies

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Bluetooth Pairing

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Industry and Standardization Bodies Near Field Communication (NFC) Technology

Short-range, high-frequency, low-bandwidth wireless connectivity standard Use magnetic field induction Operates on 13.56 MHz freq. with data transfer rate of up to 424 kbps with a

bandwidth of 14 KHz Supports two modes of communication: active-mode and passive-mode Applications: pairing two devices, smart posters, contactless-credit-cards, etc

Wireless USB Association (WUSB) WUSB group was formed in 2004 to define the WUSB specifications It is a short-range (up to 10 m), high-bandwidth wireless communication technology Replace wired USB

Wi-Fi Protected Setup (WPS) Wi-Fi Alliance officially launched Wi-Fi Protected Setup (WPS) in early 2007 Secure establishment and configuration of wireless home networks

Windows Connect now-Net Goal is to provide a way to set up secure wireless networks Works for both in-band wireless devices and out-of-band Ethernet devices

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Some Other Approaches

LoKey by Nicholson et al. , Uses SMS messages to authenticate key exchanged over the

internet Drawbacks: Delay and substantial monetary cost

Manual Authentication for Wireless Devices by Gehrmann et al. Enable handheld devices to authenticate their public keys by

some kind of user interaction User manually exchanges short message authentication codes

between the devices

A Generic Framework for Secure Device Association by Malkani et al. Device first register their capabilities with the directory service Then, client queries the directory service to discover and

acquire the required information to initiate the pairing process

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Co-locationServer

1. DeviceDescription

1. DeviceDescription

1. DeviceDescription

2. Client’sQuery

3. ServerResponse

Au

then

tica

tio

n P

roce

ss

Directory

1. DeviceDescription

3. ServerResponse

Resource(Target Device)

Client Device

Some Other Approaches

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Summary and Future Directions for Research

No single solution or standard for device pairing Too many solutions

Entering pins (e.g. Bluetooth devices) and passwords (e.g. WEP/WPA)

Comparing two audible sequences Exchanging cryptographic material through the use of

pure audio Verifying hashes of public keys Moving around and/or shaking devices together Comparing ‘Blinking’ pattern and ‘Beeping’ sequence Using SMS messages Button presses, etc.

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Summary and Future Directions for Research

Pairing protocols vary in the: Strength of their security The level of required user intervention Their susceptibility to environmental conditions Required physical capabilities of the devices Required proximity between the devices

Majority of the users are non-technical Difficult to remember the different kinds of steps

for establishing secure channel in varying situations and scenarios

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Summary and Future Directions for Research

We need to: Investigate ways of integrating different pairing protocols

within a general architecture for providing secure and usable pairing mechanisms for a large set of ad hoc scenarios

Integrate discovery mechanism into pairing schemes Design and develop new tools that can be used to

evaluate the existing as well as new pairing schemes

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