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QUANTAMCRYPTOGRAPHY
-SECRECY ENSURED
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TABLE OF CONTENT
TECHNOLOGYKEY DISTRIBUTUION
CLASSICAL
CRYPTOGRAPHY
QUANTAM
CRYPTOGRAPHY
WORKING
INTRODUCTION
SECURITY
CONCLUSION
ADVANTAGES LIMITATIONS
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INTRODUCTION
The recent application of theprinciples of quantum mechanics tocryptography has led to aremarkable new dimension in secretcommunication.
Quantum cryptography is an effortto allow two users of a common
communication channel to create abody of shared and secretinformation.
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CRYPTOGRAPHY
The whole point of cryptography is
to keep information out of the hands
of anyone but its intended recipient.
Even if the message gets intercepted,
the meaning wont be apparent to the
intercepted unless the interceptoris able to decipher it.
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Principle of Cryptography.
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A PRACTICAL EXAMPLE -
Alice wants to send a message to
Bob, without an eavesdropper Eve
intercepting the message.
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TYPE OF CRYPTOGRAPHY
CRYPTOGRAPHY
Classical Quantum
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THE CLASSICAL CRYPTOGRAPHY
Encryption algorithm and related
key are kept secret.
Breaking the system is hard due to
large numbers of possible keys.
For example: for a key 128 bits
longthere are keys to
check.
38128102 }
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THE QUANTUM CRYPTOGRAPHY
An important and unique property of
quantum cryptography is the ability
of the two communicating users to
detect the presence of any thirdparty trying to gain knowledge of
the key.
Quantum technology promises torevolutionize secure communication
at an even more fundamental level.
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THE QUANTUM CRYPTOGRAPHY
Quantum Cryptography ensuring themost secure transmission of the secretinformation works on the principle of Quantum Mechanics.
Transmission is carried out at the bitlevel with the help of various types ofalignment of the photons.
It also solves the problem of keydistribution arising in the ClassicalCryptography.
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WORKING
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QUANTUM KEY DISTRIBUTION
Auser can suggest a key by sendinga series of photons with randompolarizations. This sequence canthen be used to generate a sequence
of numbers. The process is known asquantum key distribution.
Main Features: Key distribution distance: up to 60
km
Key distribution rate: up to 1000
bits/s
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QUANTUM CRYPTOGRAPHY TECHNOLOGY
Photon Source.
Photon Detector.
Communication channel.
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PHOTON SOURCE
Photon Gun.
Light - emitting p-n junction.
Single ion.
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PHOTON DETECTOR
Avalanche photodiodes.
Germanium detectors.
Silicon.
Photo multiplier.
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COMMUNICATION CHANNEL
Fiber optical communication link.
Free space laser communication.
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SECURITY OF QKD
Quantum cryptography obtains its
fundamental security from the fact
that each qubit of information is
carried by a single photon, and thateach photon will be altered as soon
as it is read once.
This makes impossible to intercept
message without being detected.
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EFFECT OF NOISE
The presence of noise can impact
detecting attacks.
Eavesdropper and noise on the
quantum channel are
indistinguishable.
Detecting eavesdropper in the
presence of noise is hard.
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APPLICATION
E-mail messages.
Telephone calls. Financial Transactions.
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ADVANTAGES
The most important contribution of
quantum cryptography is a mechanism
for detecting eavesdropping.
Quantum key distribution enables
encrypted communications on demand,
because it allows key generation at
transmission time over an unsecured
optical communications link.
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LIMITATIONS
We have to use pure fiber optic end-to-
end network and boosters are needed at
some distance, so it is expensive.
It will also be critical to authenticate
the identity of the recipients.
It is also not clear how to modify the
scheme in order to deal with noisy
quantum transmissions.
It is hard to transmit a photon, entangled
over great distances. Photon detectors
aren't particularly reliable.
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CONCLUSION
Currently it works only over shortdistances, but there are situations in
which even short-distance transmission is
useful.Also, with sufficient technical
improvements, it might be possible in the
future to implement quantumcryptography over long distances.
The devices for implementing such
methods exist and the performance of
demonstration systems is beingcontinuously improved. Within the next
few years, such systems could startencrypting some of the most valuable
secrets of government and industry.
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