Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/hk-transfield/python-quantum-key-exchange-simulator

A simple program to simulate a Quantum Key Exchange (QKE) algorithm, written in Python3.
https://github.com/hk-transfield/python-quantum-key-exchange-simulator

cryptography encryption python python3 quantum-computing quantum-key-distribution symmetric-cryptography symmetric-encryption symmetric-key-cryptography xor-cipher xor-encryption

Last synced: about 20 hours ago
JSON representation

A simple program to simulate a Quantum Key Exchange (QKE) algorithm, written in Python3.

Awesome Lists containing this project

README 

        
# Quantum-Key Exchange



Symmetric-key cryptography requires a shared key to be known between the two parties. A simple

way to encrypt a message is XOR encryption. This method repeatedly applies the XOR operation

on the message using the key. The receiver performs the same operation to decipher the message.



But how does one transmit a key over an insecure channel? Sending it as plain text means it can

be intercepted by a malicious eavesdropper. And we can’t encrypt it because it leads to a chicken-

and-egg problem, since this operation would also require a key.



A classical solution to this problem is Diffie-Helman key-exchange algorithm. With the advent of

quantum computing, however, novel technologies have been developed. Quantum computing

manipulates quantum bits (qubits), instead of classical bits. Qubits are subject to quantum

mechanical laws of physics. In this assignment, you’ll implement and test the Quantum Key

Exchange (QKE) algorithm.



QKE assumes the existence of a quantum communication channel over which qubits can be

transferred. A qubit can be encoded via a photon’s polarization. For example, we can define

counterclockwise polarization ↺ as 1, and clockwise polarization ⟳ as 0. However, this is not the

only option, a photon could also be polarized in a linear fashion; thus, we can define an upwards

polarization ↑ as 1, and a downwards polarization ↓ as 0. Crucially, because of quantum mechanics,

the internal state of a qubit can only be measured by interacting with it through a polarization filter

of a specific type.



|                          | Qubit Value 1 | Qubit Value 2 |

| ------------------------ | ------------- | ------------- |

| **Linear Polarization**  | ↑             | ↓             |

| **Cirular Polarization** | ↻             | ↺             |



The key quantum mechanical observation is that these two types of polarization (circular vs. linear)

are orthogonal to each other. This means that if a photon is polarized in a circular manner, it has

an equal 50-50 chance to be measured as ↑ or ↓ when measured linearly (and vice-versa).



## QKE Algorithm



1. The transmitter sends a stream of qubits and for each, it records the value and polarization

   type, which are both picked randomly with equal chances.



2. The receiver receives the stream of qubits and for each, it selects a random polarization

   type to measure it, and records the results



3. The transmitter and receiver exchange the polarization types the used for the stream. The

   secret key is formed by the recorded qubit values where both happened to use the same

   polarization type. Thus, for these qubits both have recorded the same value but none but

   they know what that value actually is



---



## Installing and running the program



To run program



```

git clone https://github.com/HK-Transfield/Quantum-Key-Exchange

cd Quantum-Key-Exchange

python3 Main.py

```



To run tests



```

git clone https://github.com/HK-Transfield/Quantum-Key-Exchange

cd Quantum-Key-Exchange

pip install -r Requirements.txt

python3 -m pytest

```