Security of bluetooth
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Security of Bluetooth. Máté Szalay [email protected] Introduction. Wireless Standard Piconet (8 devices) Scatternet Range: ~10m LOS 1Mbps 64k voice 768k data 2.4 GHz v1.0, v1.1. Bluetooth SIG. Special Interest Group Founded in 1998 www.bluetooth.com Members:

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Security of Bluetooth

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Security of bluetooth

Security of Bluetooth

Máté [email protected]

Bluetooth Security


Introduction

Introduction

  • Wireless Standard

  • Piconet (8 devices)

  • Scatternet

  • Range: ~10m LOS

  • 1Mbps

    • 64k voice

    • 768k data

  • 2.4 GHz

  • v1.0, v1.1

Bluetooth Security


Bluetooth sig

Bluetooth SIG

  • Special Interest Group

  • Founded in 1998

  • www.bluetooth.com

  • Members:

    • IBM, Intel, Microsoft

    • Ericsson, Nokia, Motorola

    • Agere, 3COM, Toshiba

Bluetooth Security


Bluetooth devices

Bluetooth Devices

  • Cellular phones

  • Headsets

  • Earphones

  • Printers, keyboards

Bluetooth Security


Bluetooth security goals

Bluetooth Security Goals

  • Message Confidentiality

  • User Anonimity

  • Unique ID

Bluetooth Security


Modes of operation 1

Modes of Operation - 1

  • Discoverable

    • Replies to everyone

    • Other piconet?

    • New device?

  • Non-Discoverable

    • Replies to devices already known

Bluetooth Security


Modes of operation 2

Modes of Operation - 2

  • Connectable

    • Replies to queries from already discovered nodes

  • Non-Connectable

    • Does not reply

Bluetooth Security


Setting up communication

Setting Up Communication

  • Two devices

  • Not yet seen each other

  • Symmetric link key is set up

  • No shared secret

  • PIN based

  • Man-in-the-middle attacks

Bluetooth Security


Setting up link key

Setting Up Link Key

  • Two methods

  • 1. Insufficient Memory

    • Using the unit key as link key

    • Impersonation attacks!

  • 2. Sufficient Memory

    • Initialization key

    • Mutual Authentication

    • Exchange of random numbers

    • Link key generation

Bluetooth Security


Initialization key generation

RND a(B) PIN

RND a(B) PIN

IK

IK

CH1 a(B) IK

CH1 a(B) IK

RESP1

RESP1’

Initialization Key Generation

A

B

RND

CH1

RESP1

Bluetooth Security


Link key method 1

Link Key – Method 1

A

B

  • KA is the link key

  • Can be different from unit key!

EIK{KA}

Bluetooth Security


Link key method 2

randA a(A)

randB a(B)

LK_Ka

LK_Kb

Link Key – Method 2

A

B

  • (LK_KaLK_Kb) is the link key

  • Mutual Verification

EIK{LK_Ka}

EIK{LK_Kb}

Bluetooth Security


Link key attacks

Link Key - Attacks

  • Attacker obtains initialization key

  • PIN length!

  • Attacker obtains unit key

  • Link key computed from initialization key

  • Encryption keys are computed from link key

Bluetooth Security


Location 1

Location - 1

  • Attacker traces movement of bluetooth users

  • Owns or leases several bluetooth devices

    • $10/device

    • Well placed (airports)

  • Records identities

Bluetooth Security


Location 2

Location - 2

  • Discoverable mode

  • Non-discoverable mode

    • Wait for the user to initiate

    • Gaining control over user’s device

  • Controlling only user’s device

Bluetooth Security


Linking identities

Linking Identities

  • Consumer identity is known

    • e.g.: credit card transfer

  • Probabilistic matches

Bluetooth Security


Encryption engine

Encryption Engine

  • 4 LFSRs

    • Lengths: 25, 31, 33, 39

  • Two 2-bit registers

  • Broken:

    • 2100 time

    • 266 time + 266 memory

Bluetooth Security


Countermeasures

Countermeasures

  • PIN length > 64 bit

  • Protecting unit keys

  • Application layer security

  • Replacing the Cipher

Bluetooth Security


Thank you for your attention

Thank you for your attention!

[email protected]

Bluetooth Security


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