seminar presentation

SEMINAR REPORTPHYSICAL LAYER SECURITY IN WIRELESS

NETWORKS

IEEE Wireless Communications Journal, April 2011Authors:YI-SHENG SHIU AND SHIH YU CHANG, NATIONAL TSING HUA UNIVERSITYHSIAO-CHUN WU, LOUISIANA STATE UNIVERSITYSCOTT C.-H. HUANG, CITY UNIVERSITY OF HONG KONGHSIAO-HWA CHEN, NATIONAL CHENG KUNG UNIVERSITY

SHAANTNU ANAND149/EC/12

CONTENTS• OSI MODEL

• ABSTRACT

• OVERVIEW

• SECURITY ATTACKS

• SECURITY REQUIREMENTS

• PHYSICAL LAYER SECURITY APPROACHES

• COMPARISON

OSI MODEL (1)• Conceptual model that standardizes the communication functions of a

telecommunication system.

OSI MODEL (2)• The Physical layer : Transmission and reception of bit streams over a

physical medium . In wireless communications the physical layer can also be radio waves and infrared light.

• CRYPTOGRAPHY :

ABSTRACT (1)• Wireless Network : Any type of a computer network using wireless data

connections for connecting network nodes.

• Wireless networks are generally implemented using radio communication.

ABSTRACT (2)• In today's age wireless communication plays an extremely important

role in civil and military applications.• The transfer of confidential information over wireless networks is a

challenging task. • Thus , it becomes essential that data is only accessible to the intended

users. • The two most prevalent attacks at the physical layer are jamming and

eavesdropping.

OVERVIEW (1)• Wireless communication is an indispensible part of our daily life.• Security is now a critical issue when it comes to transmission of

important private information such as electronic transactions and banking related data communications.

• Most commonly used methods to ensure security rely on cryptographic techniques employed at the upper layers of the OSI model.

• A secure channel is required for key exchange to implement the cryptographic technique.

• Instead of using an additional layer the physical layer method can be employed to distribute secret keys, supply location privacy and to supplement upper layer algorithms.

• The application of physical layer security schemes makes it more difficult for attackers to decipher transmitted information.

OVERVIEW (2)• Existing physical layer security techniques can be classified into five major

categories :(1) Theoretical secure capacity(2) Power approach(3) Code approach(4) Channel approach(5) Signal Detection approach

• Physical layer can have some built-in security to assist the traditional upper layer encryption techniques.

• This seminar report aims at evaluating and comparing the physical layer security methods based on two metrics .

• First, secret channel capacities and second, computational complexities.

SECURITY ATTACKS (1)• Most attacks are classified into two major categories :

SECURITY ATTACKS (2)Passive Attacks

•Intruder/adversary’s objective is to steal information from wireless networks.•Network operation is not disrupted.•Types : (1) Traffic analysis (2) Eavesdropping intrusion.

Active Attacks

• Adversary tries to alter the communication data.• Interferes with the normal network operation.•Types : DoS, Masquerade, Information disclosure, replay, message modification,Resource consumption.

SECURITY ATTACKS (3)• ACTIVE ATTACKS :(1) Denial of Service (Dos) : An intruder tries to exhaust the resource

available to its legitimate users. • At the physical layer, radio frequency jamming is used to occupy the

transmitted signal band.• In this way the communication is disrupted and an adversary makes the

attacked nodes suffer from DoS.

SECURITY ATTACKS (4)(2) Masquerade attacks : In a masquerade attack an intruder deceives the

authentication mechanism and pretends to be a legitimate user thus disrupting the communication .

(3) Information Disclosure and Message Modification : A compromised node acts as an information leaker.

• Information such as periodicity of traffic between two nodes can be valuable to an intruder.

• Message modification refers to addition or deletion of network communication content by an adversary.

SECURITY ATTACKS (5)• PASSIVE ATTACKS(1) Eavesdropping : It is the unauthorized real-time interception of private

communication such as a phone call or instant message.• Generally encryption is used to overcome this problem. (2) Traffic Analysis : Process of intercepting and analyzing messages in order

to deduce patterns in communication.• The greater the number of messages stored the more can be inferred

form the traffic.• Traffic analysis can also be done with encrypted information.

SECURITY ATTACKS (6)• A typical passive attack is shown below :

SECURITY REQUIREMENTS (1)• Services in a wireless communication system should satisfy certain

requirements.

(A) AUTHENTICATION AND NON-REPUDIATION• Authentication is used to confirm that a communication request comes

from a legitimate user. • Types : (1) Entity Authentication - Justifies identity of parties in the system. (2) Data origin Authentication – Confirms the identity of data

creator.• Non-repudiation guarantees that the transmitter of a message cannot deny

having sent it.• Similarly the recipient cannot deny having received it. Example : digital

signature.

SECURITY REQUIREMENTS (2)(B) CONFIDENTIALITY AND ACCESS CONTROL• Confidentiality is the protection of data to prevent access to

unauthorized users.• Encryption ensures that data is accessible to intended users only.• Access control limits and controls devices that have access to

communication links.

SECURITY REQUIREMENTS (3)(C) INTEGRITY AND AVAILABILITY• Trustworthiness and reliability of information.• Integrity means data that was sent is exactly the same as to what was

received.• Availability : Communication should remain fully operational when a

legitimate user is trying to communicate.

SECURITY REQUIREMENTS (4)(D) RESISTANCE TO JAMMING • Jamming is a simple technique to interfere with communication

channels.• A jammer may send out interference signals which disrupt signal

reception.• Active jammers send out continuous radio signals into the channel and

thus block the communication of users.• Reactive jammers sit idle till the time they sense transmission in the

channel.• As soon as this happens they send out jamming signals.

SECURITY REQUIREMENTS (5)(E) RESISTANCE TO EAVESDROPPING • Typical secrecy problem :

• Hiding information is a method to embed private information into background signal or noise process.

TRANSMITTER

EAVESDROPPERR

RECEIVER

PHYSICAL LAYER SECURITY APPROACHES (1)

• Physical layer security approaches are divided into five major categories :

(1) Theoretical Secure Capacity(2) Channel Approach(3) Coding Approach(4) Power Approach(5) Signal Design Approach


(A) THEORETICAL SECURE CAPACITY• Secrecy Capacity : maximum rate achievable between a transmitter-

receiver pair subject to information attainable by the unauthorized receiver (or intruder).

• The theoretical secure capacity approach is basically the information –theoretic security approach.

• A huge amount of research is still going on in this field.• This approach requires complete knowledge of the communication

channels ( e.g. : Gaussian or memory less) • A few systems have been deployed but this technology is largely

unavailable due to high implementation cost.


(B) CHANNEL APPRAOCHES(i) R F Fingerprinting : This system consists of multiple sensor systems that

capture and extract RF features from each received signal.• An intrusion detection system processes the feature sets and generates

a dynamic fingerprint for each internal source identifier derived from a few packets.

• This RF system monitors the temporal evolution of each fingerprint and issues an alert when a strange fingerprint is detected, thus distinguishing an intruder.


(ii) ACDM Precoding : Transmitted code vectors are generated by singular value decomposition (SVD) of the correlation matrix which describes the channel characteristics between transmitter and receiver.

• SVD : Singular value decomposition is a factorization of a real or complex matrix

• The transmitted message is sent in terms of blocks and then modulated in order to provide high-data-rate communication.


(iii) Randomization of MIMO transmission coefficients : • The transmitter generates a diagonal matrix dependent on the impulse

response of the transmitter receiver channel.• The diagonal matrix has the unique property of being undetectable to an

intruder.• Reduces signal interception.


(C) CODE APPROACH• Main objective is to improve resilience against jamming and

eavesdropping.(i) Error Correction Coding : • A single error in the received ciphertext will cause a large number of

errors in the decrypted plaintext.• In order to overcome this problem a scheme with encrypted turbo

coding is used.• A secure communication channel is set up based on selecting N pseudo

random bits from M encoded bits.


(ii) Spread Spectrum Coding :• Spread spectrum coding is a signaling technique in which a signal is

spread by a noise sequence over a wide frequency band with frequency greater that that of the original signal.

• Traditional cryptographic techniques can have a large key size however, spread spectrum system is limited to range of carrier frequencies.

• In the CDMA ( Code-division multiple access) system all users share the same channel using different spreading codes to distinguish their signals.


(D) POWER APPROACH• Data protection can also be facilitated using power approaches. The

usual schemes in these approaches involve the employment of directional antennas and the injection of artificial noise.

(i) Directional Antenna : • Beam width is inversely proportional to peak gain in a directional

antenna.• If a directional antenna is used a node can receive data from directions

not covered by a jamming signal.• Thus, directional antennas improve network capacity, avoid physical

jamming attempts and enhance data availability.


(ii) Artificial Noise Scheme : • Perfect secrecy can be achieved when the intruders channel is noisier

than the receivers channel.• Artificial noise is utilized to impair the intruder’s channel, but it does not

affect the receiver’s channel since the noise is generated in the null-space of the receiver’s channel.

Receiver’s channel ( noise generated in null spaces)

Noisier channel

ReceiverTransmitter

Intruder


(E) SIGNAL DESIGN APPROACH• Consider a network that consists of multiple antenna transmitter and

several single antenna receiver (receiver and eavesdropper).• Transmitter has knowledge of the channel and the receiver’s feedback is

recorded.• Artificial Noise scheme is utilized and quality of service (Qos) can be

obtained by using higher modulation or higher error correction codes.

COMPARISON (1)SECURITY SCHEMES RESISTED ATTACKS ACHIEVED SECURITY

REQUIREMENTRF fingerprint Eavesdropping, resource

consumption, masqueradeAuthentication confidentiality

Rand MIMO Eavesdropping Confidentiality

AES CDMA Eavesdropping Confidentiality

ACDM (algebraic channel decomposition multiplexing)

Eavesdropping Confidentiality

FHSS (frequency hopping spread spectrum)

Jamming, eavesdropping, trafficanalysis

Availability confidentiality

Pseudo-chaotic DS/SS (spread spectrum direct)

Eavesdropping, traffic analysis

Confidentiality

Artificial Noise Eavesdropping Confidentiality

COMPARISON (2)• The comparison is based on some assumptions .• The assumptions include that an unauthorized user has a much worse

channel than that of an intended user, or has no idea about the spreading codes or channel characteristics.

• The comparison of the prevalent techniques is done on the basis of two metrics .

(i) Secret Channel Capacity :• Low probability of interception (LPI) is an important factor in physical

layer security.• Secret channel capacity is defined as; an intruder will acquire no more

information than a random guess from the communication than an intended receiver at some given information rate.

COMPARISON (3)(ii) COMPUTATIONAL COMPLEXITY• Intruder cannot obtain information in encrypted transmission without

the secret key.• Larger the number of the keys , higher is the security level.• Computational complexity becomes an issue when receivers have to

decrypt all messages, thus data authentication is employed to distinguish between intruders and transmitters.

CONCLUSIONS• Existing physical layer security approaches have been compared on two

metrics namely, secret channel capacity and computational complexity.• Due to hardware complexity the low cost implementation of most

physical layer security schemes is still beyond the capability of current microelectronic technologies.

• FUTURE WORK :• The existing physical layer security can be improved upon by catering for

multi user access and cross – layer protocols.• The security approaches can also be put through cryptanalysis to test

their strength.

seminar presentation

Documents