Device-to-Device Authentication Nitesh Saxena Polytechnic Institue of NYU.
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Transcript of Device-to-Device Authentication Nitesh Saxena Polytechnic Institue of NYU.
The Problem: “Pairing”
How to bootstrap secure communication between Alice’s and Bob’s devices when they have no prior context no common trusted CA or TTP
Examples (single user setting)
Pairing a bluetooth cell phone with a headset
Pairing a WiFi laptop with an access point
(In)Security of PIN-based Pairing
Long believed to be insecure for short PINs Why?
First to demonstrate this insecurity; Shaked and Wool [Mobisys’05]
Attack Implementation
Coded in C on linux platform Given a piece of code for SAFER algorithm,
implemented the encryption functions E22, E21, E1
Hardware for sniffing: bluetooth packet analyzer with windows software
Log Parser (in perl): reads the sniffer log, and parse it to grab IN_RAND, RAND_A \xor Kinit, RAND_B \xor Kinit, AU_RAND_A, AU_RAND_B, SRES
Timing Measurements of Attack Theoretically: O(10^L), with decimal digits
Assuming the PINs are chosen uniformly at random Empirically, on a PIII 700MHz machine:
No. of digits in PIN (L)
CPU time (sec)
4 1.294
5 12.915
6 129.657
7 1315.332
Timing of Attack and User Issues
ASCII PINs: O(90^L), assuming there are 90 ascii characters that can be typed on a mobile phone Assuming random pins
However, in practice the actual space will be quite small Users choose weak PINs; User find it hard to type in ascii characters on
mobile devices Another problem: shoulder surfing (manual or
automated) Yet another problem: hard-coded PINs
The Problem: “Pairing”
Idea make use of a physical channel between devices with least involvement from Alice and Bob
Authenticated: Audio, Visual, Tactile
Seeing-is-Believing (McCune et al. [Oakland’05])
Protocol (Balfanz, et al. [NDSS’02])
A B
pkA
pkB
H(pkA)
H(pkB)
Insecure Channel
Rohs, Gfeller [PervComp’04]
Secure if H(.) weak CR
80-bit
Authenticated Channel
Challenges
OOB channels are low-bandwidth! One of the device might not have a receiver! Neither has a receiver and only one has a
good quality transmitter (Non-)Universality!
Usability Evalutation! Protocols might be slow – multiple executions! Multiple devices – scalability!
Challenges
OOB channels are low-bandwidth! One of the device might not have a One of the device might not have a
receiver!receiver! Neither has a receiver and only one has Neither has a receiver and only one has
a good quality transmittera good quality transmitter (Non-)Universality!(Non-)Universality!
Usability!Usability! Multiple devices -- scalabilityMultiple devices -- scalability
Protocol: Short Authenticated Strings (SAS)
A B
pkA,cA
pkB,cB
dA
dB
Secure (with prob. 1-2-k )
Insecure Channel
Authenticated Channel
SASA
SASB
cA,dA comm(pkA,RA)
RA ε {0,1}k
RB ε {0,1}k
cB,dB comm(pkB,RB)
SASA = RA RB
SASB = RA RB
Accept (pkB,B) if
SASB = RA RB
Accept (pkB,A) if
SASA = RA RB
Vaudenay [Crypto’05]
RA open(pkA,cA,dA)
RB open(pkB,cB,dB)
Laur et al. [eprint’05]
Pasini-Vaudenay [PKC’06]
Challenges
OOB channels are low-bandwidth!OOB channels are low-bandwidth! One of the devices might not have a
receiver! e.g., keyboard-desktop; AP-phone
Neither has a receiver and only one has Neither has a receiver and only one has a good quality transmittera good quality transmitter (Non-)Universality!(Non-)Universality!
[Usability!][Usability!] Multiple devices -- scalabilityMultiple devices -- scalability
Unidirectional SAS (Saxena et al. [S&P’06])
A B
pkA , H(RA)
pkB, RB
RA
hs(RA,RB;pkA,pkB)Galois MAC
Success/Failure
Secure (with prob. 1-2-15) if 15-bit AU hs()
Blinking-LightsInsecure Channel
Authenticated Channel
User I/O
Muliple Blinking LEDs (Saxena-Uddin [ICICS’08])
Challenges
OOB channels are low-bandwidth!OOB channels are low-bandwidth! One of the device might not have a One of the device might not have a
receiver!receiver! Neither has a receiver and only one has
a good quality transmitter e.g., AP-laptop/PDA
[Usability!][Usability!] Multiple devices -- scalabilityMultiple devices -- scalability
A Universal Pairing Method Prasad-Saxena [ACNS’08] Use existing SAS protocols The strings transmitted by both devices over
physical channel should be the same, if everything is fine different, if there is an attack/fault
Both devices encode these strings using a pattern of Synchronized beeping/blinking The user acts as a reader and verifies if the two
patterns are same or not
Is This Usable?
Our test results are promising Users can verify both good test cases and bad
ones Blink-Blink the easiest
Very low errors (less than 5%) Execution time ~22s
Then, Beep-Blink Very low errors with a learning instance
(less than 5%) Execution time ~15s
Beep-Beep turns out error-prone
Further Improvement: Auxiliary Device
Saxena et al. [SOUPS’08]
Auxiliary device needs a camera and/or microphone – a smart phone Does not need to be trusted with cryptographic data Does not need to communicate with the devices
A B
S
ucce
ss/F
ailu
re
Further Improvement: Auxiliary Device
Blink-Blink ~14s (compared to 22s of manual scheme)
Beep-Blink Approximately takes as long as the same as
manual scheme No learning needed
In both cases, False negatives are eliminated False positives are reduced
It was preferred by most users
Challenges
OOB channels are low-bandwidth!OOB channels are low-bandwidth! One of the device might not have a One of the device might not have a
receiver!receiver! Neither has a receiver and only one has Neither has a receiver and only one has
a good quality transmittera good quality transmitter (Non-)Universality!(Non-)Universality!
Comparative Usability! Multiple devices -- scalabilityMultiple devices -- scalability
Selected Methods (Kumar et al. [Percom’09; PMC’09])
Manual Comparison Numbers (Uzun et al. [USEC’06]) Spoken/Displayed Phrases
L&C (Goodrich et al. [ICDCS’06]) Images (Random Arts) (Perrig-Song [Cryptec’99]) Synchronized Comparison (Prasad-Saxena
[ACNS’08]) Manual Transfer
BEDA (Soriente et al. [IWSSI’07]) Automated
SiB (McCune et al. [S&P’05]) Blinking Lights (Saxena et al. [S&P’06]) Audio Transfer (HAPADEP) (Soriente et al. [ISC’08])
Tested Methods: Manual Comparison
Number Comparison “65473” =? “75853”
Phrase Comparison “Alice buys jackets” =? “John likes elephants”
Image Comparison
=?
Tested Methods: Manual Comparison
Loud and Clear (L&C) variants Speaker-Speaker
=?
Display-Speaker
=?
John buys a
car
John buys a
car
John buys a
car
John buys a car
Button enabled (BEDA) methods LED-Button
Vibrate-Button
Button-Button
Tested Methods: Manual Transfer/Entry
Tested Methods: Automated Transfer
Seeing is Believing (SiB)
Blinking Lights
… … ….. HAPADEP Variant
Study Results: Fatal Errors
*Cases with 0% fatal errors are removed from the table
Method name Specific test case Avg. fatal error rate
Image Comparison Mismatched Images 0%
Number Comparison*First Digit Mismatch 10%
Middle Digit Mismatch 5%
Phrase Comparison*2-Word Mismatch 5%
Middle Word Mismatch 5%BEDA (Led-Button) Reject Signal 0%
BEDA (Vibrate-Button) Reject Signal 0%Loud & Clear (Display-Speaker)* First Word Mismatch 5%
Loud & Clear (Speaker-Speaker)*
2-Word Mismatch 5%First Word Mismatch 10%Last Word Mismatch 5%
Audio/Visual (Beep-Blink)*First Bit Mismatch 20%
Middle Bit Mismatch 5%
Audio/Visual (Blink-Blink)*
4-Bit Mismatch 5%First Bit Mismatch 30%
Synchrony Bit Mismatch 5%Middle Bit Mismatch 5%
Study Results: Safe ErrorsMethod name Specific test case Avg. completion
time (seconds)Avg. safe error rate
Image Comparison Matching Images 12.7 (sd*=10.7) 15%Number Comparison Matching Numbers 8.6 (sd=4.9) 0%Phrase Comparison Matching Phrases 12.7 (sd=8.0) 10%
BEDA (Led-Button) Accept Signal 49.5 (sd=27.5) 0%
BEDA (Vibrate-Button) Accept Signal 44.3 (sd=18.0) 0%
Loud & Clear (Display-Speaker) Matching Phrases 15.5 (sd=6.3) 0%
Loud & Clear (Speaker-Speaker) Matching Phrases 21.3 (sd=6.8) 0%
Blinking Lights Accepting Receving Device 28.8 (sd=10.4) 0%Seeing Is Believing Accepting Receving Device 26.9 (sd=7.5) 5%
Audio/Visual (Beep-Blink) Matching Patterns 26.3 (sd=5.3) 5%
Audio/Visual (Blink-Blink) Matching Patterns 27.8 (sd=10.3) 0%
HAPADEP Variant Accepting Receving Device 10.8 (sd=2.6) 5%BEDA (Button-Button)
Normal Protocol Behavior Until Pairing Is Successful 31.9 (sd=32.1) N/A
*Estimated Standard Deviation from the sample
Conclusions from the Study Users did not like camera-based methods Best overall choices when:
both devices have a displayNumeric Comparison Phrase Comparison >= Image Comparison
one device doesn’t have a display but an audio interfaceHAPADEP (if microphone is available on one, and speaker on the
other)L&C Display-Speaker (if one has a display and the other has a
speaker. device(s) are highly interface constrained
BEDA Vibrate-Button if possibleBEDA LED-Button otherwise
Challenges
OOB channels are low-bandwidth!OOB channels are low-bandwidth! One of the device might not have a receiver!One of the device might not have a receiver! Neither has a receiver and only one has a Neither has a receiver and only one has a
good quality transmittergood quality transmitter (Non-)Universality!(Non-)Universality!
[Usability!][Usability!] Protocols might be slow – multiple executions!Protocols might be slow – multiple executions! Multiple devices – scalability
Bootstrapping key pre-distribution on sensors