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Secure Communication Over Fiber Optic Networks
Fiona RozarioD Y Patil School of Engg. &
TechnologyM.E. (CN) – I
22nd March, 2016
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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
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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
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What are optical fibers?
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Working principle of optic fibers
Total internal reflection
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Fiber optic communication system
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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
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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
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Security Issues
Attacks aimed at: Network transmission – tapping, jamming
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Security Issues – Direct attacks
Attacks aimed at: Optical amplifiers – jamming
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Security Issues – Direct attacks
Attacks aimed at: Optical cross-connects – in-band and out-of-band
crosstalk
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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
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What is encryption?
Mathematical altering data (plaintext) in a consistent manner to form a unintelligible ciphertext
Reversible processRelies on a secret key
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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
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Encryption schemes
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Optical encryption schemes
Optical CDMAQuantum cryptographyChaos based encryptionsSteganography
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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.
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Coherent OCDMA
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Incoherent OCDMA
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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
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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
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Chaos based encryption
Masks the confidential data with stronger chaos
Enhances robustness of data transmission
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Steganography
Aim – to hide the signal in the existing public channels; hacker should be unable to detect the presence of a signal
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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
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Steganography
Approach 2 – Add temporal phase masks
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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
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Conclusion