This ppt was prepared for a Seminar .It covers all the basic of Cryptography as well as Quantum Cryptography .

1. Quantum Cryptography
Presented By -
Swasat Dutta
Gau-C-15/L-381
B.Tech 7th Sem

2. Cryptography
Crypto – Secret
Graphy – Writing

5. ● In Symmetric cryptography same key is used for encyption and
decryption . If key is leaked then communication is not secured.
● In Asymmetric cryptography , keys used are at least 128-bit keys which
are considered to be very strong .To generate a private key for that
public key involves huge amounts of calculations.
WHY DO WE NEED QUANTUM CRYPTOGRAPHY

6. ● Quantum cryptography has a different way of sending the key to the
receiver. It uses photons to send a key .
● Polarization - The ability of waves to oscillate in more than one
direction
Quantum Cryptography
0
01
1
Diagonal
Polarization mode
Rectilinear
Polarization mode

7. The Quantum Cryptosystem : Basic Operation
1. “Alice” prepares a series of photons with random polarizations – either 45,
90, 135, or 180 degrees. She sends these photons to “Bob” over a quantum
channel.
2. Bob measures the photons. He randomly chooses a filter by which to
measure the incoming photons, and records which filter he used. If he
measures 45 or 90 degrees, a 0 bit is recorded; if he measures 135 or 180
degrees, a 1 bit is recorded.
3. Using a normal, unsecured channel, Alice and Bob communicate to find
which bits Bob used the correct filter for. These values are now become a
secret key between Alice and Bob.
4. Error correction processes performed by Alice and Bob .

8. Key-1 0 0 1 0 1 00 Key-1 0 0 1 0 1 00
ALICE BOB

9. Detecting an Eavesdropper
● Heisenberg’s uncertainty principle states that it is impossible to measure
together the speed and position of a particle with highest accuracy, and its
state will change when measured.
● Measuring one variable will necessarily affect the other. Polarization
properties of light fall into this category, therefore, an interloper who is trying
to intercept and measure the optical signal will invariably affect the system in
a such a way that their interference will be noticed.

10. Conclusion
Privacy and data security is right now of utmost importance to
people. With quantum cryptography, secure transmission of data is
possible, and chances of it being intercepted and altered are very low.
This technology has been implemented in some areas. But is still under
deeper research before being widely implemented.

11. References
● www.studymafia.org
● www.technologyreview.com
● www.seminarsonly.com
● www.popsci.com

12. THANK YOU