1. Quantum Computing and Cryptography
Vishal Bilagi
Kennesaw State University

2. Modern Day Cryptography
Relies on mathematical formula to secure data
Easy to create cryptographic keys, but hard to randomly guess because of the integer factorization problem
Pretty good at keeping data encrypted since classical computers can take forever to guess the encryption keys
What can crack such cryptographic keys easily?
Quantum computers are very efficient at doing this task
Kennesaw State University

3. Quantum Computing Impact on Modern Day Cryptography
Poses a threat to asymmetric key cryptographic systems
Proven theory exists that a quantum computer can factorize integers that form an encryption key
In 2001, Shor’s algorithm factorized 15 = 5 x 3 and in 2012, 21 = 3 x 7
A quantum computer with sufficient qbits can actually crack RSA encryption one day.
Quantum computing is not a serious threat to symmetric key cryptographic systems
Grover’s algorithm offered a quadratic speed up to crack a 128-bit encryption key in 264 iterations.
Since there is no basis on where to begin guessing the key, it is harder to crack symmetric encryption keys
Doubling the key size should still keep the currently used symmetric key encryption pretty unbreakable
Building and maintaining a Quantum computer is very expensive and there is really low chance in the given years that it poses a serious threat to cryptosystems
Kennesaw State University

4. Post Quantum Cryptography
In the coming decades, when quantum computing advancements reach new level, only then will it be a threat to existing cryptosystems
In order to tackle such a case, a new way to securely store and transmit data needs to be employed
A transmission medium that quantum computers can securely communicate in
Such a paradigm shift is termed as Post Quantum Cryptography
New algorithms that harness the power of quantum mechanics to secure data
Communication medium that works well between quantum computers
Kennesaw State University

5. Post Quantum Cryptography Approach
Lattice-based Cryptography
Multivariate cryptography
Hash-based cryptography
Code-based cryptography
Supersingular elliptic curve isogeny cryptography
Symmetric key quantum resistance
Kennesaw State University

6. Quantum Key Distribution
A new medium of communication needs to be established and agreed upon the quantum computers that are in it
For this new network medium, keys need to be shared with the authorized parties on the network
Transmitting quantum data across this medium and making some sort of handshake involves a protocol called Quantum Key Distribution (QKD)
Keys are randomly generated and agreed between two parties that want to communicate with each other
One major advantage of quantum key exchange is that it allows the parties to detect intruders in the system by analyzing any anomaly caused by eavesdropping – this is based on the ‘No Cloning Theorem’
Kennesaw State University

7. Quantum Cryptography Algorithm – BB84
In 1984, Charles Bennett and Gilles Brassard published a paper, outlining a protocol for sharing/generating random secret keys on a quantum communication network
Keys are random because both the parties are unaware of what the key will be until they have a discussion after transmission and reception bits
In this protocol each bit is encoded using photons. Specifically in two polarization bases – Rectilinear or Diagonal
For rectilinear bases bit 0 is polarized as 0 degrees, bit 1 is polarized as 90 degrees
For diagonal bases bit 0 is polarized as 45 degrees, bit 1 is polarized as 135 degrees
90, bit 1
45, bit 0
135, bit 1
0, bit 0
Kennesaw State University

8. BB84 – How It Works
Kennesaw State University

9. Thank you
Kennesaw State University