By Wajeeha Ahsan
The second talk in the series of talks by final year students arranged by NPAS was held on 7th of May on MS Teams.
The session started with Alizah Gul Memon, a final year student of BS Physics, introducing her final year project to the audience. The major topics discussed in the session were Quantum Computing, Advance Encryption Standard, Quantum Circuits and also the future direction of Alizah’s project. Alizah started with some basics about Quantum Mechanics and how phenomenon of Superposition, Entanglements and Interference are used in Quantum Mechanics. Phenomenon of superposition was explained well by the Schrodinger’s cat experiment. Entanglements is when group of particles interact in way such that quantum state of each particle cannot be described independently. It’s as if both particles are connected in way. Waves superpose in interference.
In Quantum Computing, we use laws of QM just like the universe in a system. QC is being explored quite a lot to find ways so that Quantum computers can outclass classical computers. So many countries and companies came forward with their share of work in Quantum world and achieved quantum supremacy.
Alizah mentioned that there are threats to principles on which encryptions is done. Popular algorithms used to involve integer factorization problems, discrete logarithm problems etc. As quantum computers are evolving, soon classical algorithms will be threatened. That’s why there is strong need of algorithms which will be safe for post quantum environment. So there is Grover’s Algorithm which speeds up attacks against symmetric ciphers.
Alizah described what AES is and how it works in detail. AES is Advance Encryption Standard and it is relatively safe. It is used by WhatsApp and US government as well. Instead of encrypting and decrypting information bit by bit, it interacts with information in form of blocks. It takes plain text and prints it into cipher text. Hexadecimal notation is used as opposed to binary. In the encryption, we have an initial state and when we use different operations using our cipher key to jumble the information up so that it’s secured. The operations are performed again and again until we have cipher text in the end. Then bytes are substituted from the table. Rows are shifted and then columns are multiplied by a matrix. This multiplication is not ordinary. AddRound key is obtained for each of the column. Few more operations are performed to secure the information. Hence AES is interesting and complex at the same time just like a Rubik’s Cube.
Quantum Circuits are built by gates and they determine the cost. More the qubits involved, more is the cost of circuit. There are two methods to calculate the quantum cost. One cost015 metric and other is cost115 metric. Alizah did the comparison by the smart use of Jenga. There are some qubits which are not required after usage so we can use them somewhere else so it makes our circuit cost efficient.
The future prospect Alizah gave us was to think of more cost efficient circuit with lesser number of qubits and gates and finally we would be able to crack the uncrackable AES.
The session was concluded with some interesting questions from the audience which Alizah answered proficiently.
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