Secure Communication Over Fiber Optic Networks

Fiona RozarioD Y Patil School of Engg. &

TechnologyM.E. (CN) – I

22nd March, 2016

Contents

Optical Fiber Networks What are optical fibers? Working principle of optical fibers Types of optical fibers Fiber optic communication system Advantages of using fiber optics in communication Security issues in fiber optic networks

Encryption systems What is encryption? Encryption schemes Optical cryptography Steganography

What are optical fibers?

A flexible, transparent fiber made of glass or plastic

Slightly thicker than human hair

Its function is to guide visible and infrared light over long distances

What are optical fibers?

Working principle of optic fibers

Total internal reflection

Fiber optic communication system

Advantages of fiber optics in communication networks

• Longer life than copper wire• Nominal handling and installation costs • Unaffected by electromagnetic interference • Attenuation much lower than coaxial cable or

twisted pair (about 0.2dB/km)• No issue of protecting against grounding and

voltage problems• Higher BW offered

Security Issues

Network attacks can be classified as: Service disruptions: prevents communication or

degrades QoS Tapping: unauthorized access to data, compromises

privacy

Physical layer attacks Direct attacks: characteristics of physical elements

changed Indirect attacks: introducing crosstalk

Security Issues

Attacks aimed at: Network transmission – tapping, jamming

Security Issues – Direct attacks

Attacks aimed at: Optical amplifiers – jamming

Security Issues – Direct attacks

Attacks aimed at: Optical cross-connects – in-band and out-of-band

crosstalk

Security in optical networks

Security –

Physical security – ensures minimum privacy of data and QoS

Semantic security – protects meaning of the data even if it has already been reached by the attacker

Deals with cryptopraphy

What is encryption?

Mathematical altering data (plaintext) in a consistent manner to form a unintelligible ciphertext

Reversible processRelies on a secret key

Encryption schemes

Building blocks of all cipher algorithms:• Substitution – replace

bits/characters/blocks of data with substitutes

• Transposition - rearrange replace bits/characters/blocks of data

Encryption schemes

Optical encryption schemes

Optical CDMAQuantum cryptographyChaos based encryptionsSteganography

Optical CDMA

• An optical short pulse is spread over a one-bit duration T by encoding.

• The decoding time despreads the signal, reconstructing the signal if the codes between the encoder and decoder match.

• The signal remains spread over T if the codes do not match.

Coherent OCDMA

Incoherent OCDMA

Elements of Quantum Cryptography

Light waves are propagated as discrete quanta called photons.

They are massless and have energy, momentum and angular momentum called spin.

Spin carries the polarization – plane in which the electric field oscillates.

Photons of different polarizations represent the different quantum states

Polarization basis is the mapping we decide to use for a particular state

Quantum Cryptography

Deals with secure key distributionKey transmitted at a lower rate than data but

at a higher security levelKey information is coded onto the quantum

states of a photon

Chaos based encryption

Masks the confidential data with stronger chaos

Enhances robustness of data transmission

Steganography

Aim – to hide the signal in the existing public channels; hacker should be unable to detect the presence of a signal

Steganography

Approach 1 - temporally stretch a short optical pulse through

chromatic dispersion

Without the correct dispersion compensation at the receiver, signal stays buried in the noise of the public channel

Attacker can use tunable dispersion compensating device to check presence of stealth signals

Fine tune the device to retrieve the stealth signal

Steganography

Approach 2 – Add temporal phase masks

Steganography

Approach 3 - Employ ASE noise from amplifiers

ASE noise from EDFA is most prevalent in optic systems

ASE noise carrying stealth signal and ASE noise already existing in the system have identical spectral properties

Eavesdropper cannot differentiate between the two ASE noises

Conclusion