2025/26: Segurança em Sistemas Informáticos (Computer Systems Security) - 1.o M.EIC

Lab 8: Quantum Security Start

Starting with Quantum Cryptography: quantum key distribution

Goal

Experimenting a basic Quantum Distribution Cryptographic scheme, the BB84 protocol, in a real quantum computer made available by IBM (via Qiskit, Quantum Information Science Kit).
The results should allow the validation of the BB84 protocol with real data.

Procedure

This is the "workflow" suggested:

1. Create account in IBM Quantum Platform
   • https://quantum.cloud.ibm.com/
     • Sign-in ...
   • https://quantum.cloud.ibm.com/
     Welcome to the IBM Quantum Platform
     • Create your free instance to get started ...
     • Dashboard (https://quantum.cloud.ibm.com/)
       • Create API key ...
2. Activate a Python virtual environment
   • https://quantum.cloud.ibm.com/docs/en/guides/install-qiskit#local
     • mkdir qiskit
     • qiskit$ sudo apt install python3.12-venv
     • qiskit$ python3 -m venv .venv
     • qiskit$ source .venv/bin/activate
3. Install and set up Qiskit and Qiskit Runtime
   • https://quantum.cloud.ibm.com/docs/en/guides/install-qiskit
     (also, https://pypi.org/project/qiskit/)
     • (.venv) qiskit$ pip install qiskit
4. "Qiskit in the classroom: Quantum key distribution"
   • https://quantum.cloud.ibm.com/learning/en/modules/computer-science/quantum-key-distribution
     Dr. Katie McCormick
     https://youtu.be/R0SOqLwLOR0?si=a0AujghPklDN4iBb
   • 4.1 Install the needed Python packages
     • (.venv) qiskit$ pip install qiskit-ibm-runtime
     • (.venv) qiskit$ pip install numpy
     • (.venv) qiskit$ pip install matplotlib pylatexenc
   • 4.2 Read the text (most of which is about the "one-time pad"...), specially in the parts related to the coding of the BB84 protocol's experiment.
   • 4.3 Edit the code as you think fit, taking in consideration the "Remarks" ahead and run them on the Quantum computer! Also remember that the print() function is a very good friend! ;-)
     

Remarks

• There are several "bugs" in the text and in the code. Be attentive and pacient.
• The text talks about simulating the first two experiments ("Experiment 1: QKD with no eavesdropper", "Experiment 2: QKD with an eavesdropper") and running in actual quantum hardware the last two experiments ("Experiment 3,4: Compare QKD with and without eavesdropping on a real quantum computer"). In fact, the supplied uncommented code _uses_ the real quantum computer right away:
  • (...)
    job = sampler.run([qc_isa], shots=1)
#job = sampler_sim.run([qc], shots = 1)
    (...)
• Probably, it is better to forget the Simulator and use the quantum computer right away, as the running time of these experiments is very small (usually, just a few seconds). I remind that a person has, for free, 10 mn of real quantum computer usage per month!
• An experiment with 20 bits (or so) makes it easier to look at the values; but a more realistic experiment should use much more bits - at the current moment the computers support up to 156 qubits, so, you could use 128 bits easily with this simple experiments.
• For accessing the Quantum computer, I would recommend the simple call:
  • service = QiskitRuntimeService(token=<your-api-key>,
    # Use the 44-character API_KEY you created and saved from the IBM Quantum Platform Home dashboard
instance=<IBM Cloud CRN>
    # use the CRN, Cloud Resource Name, you get from the IBM Quantum Platform Home dashboard, in https://quantum.cloud.ibm.com/)

Report

Analyze the results you obtained both with and without "eavesdropping", compare them with what was expected for the BB84 protocol and write a short report stating your findings and insights gained.
Email the group's report to the teacher, carefully identifying the group and Lab.

Appendices

Example of results obtained with "print()"

• "no eavesdropping", 20 bits
  (.venv) qiskit$ python 5.1.py
Alice's bits are [0. 1. 0. 1. 1. 0. 1. 0. 1. 1. 1. 1. 1. 0. 0. 0. 0. 0. 1. 1.]
Alice's bases are [1. 0. 0. 0. 0. 0. 1. 1. 0. 1. 0. 1. 0. 1. 1. 1. 0. 0. 0. 0.]
Bob's bases are [1. 1. 1. 0. 0. 0. 1. 1. 0. 0. 1. 0. 0. 1. 1. 1. 1. 1. 1. 0.]
qiskit_runtime_service._discover_account:WARNING:2026-04-30 15:20:58,427: Loading account with the given token. A saved account will not be used.
ibm_fez
Bob's measured = [0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1]
Alice's bits = [0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1]
Bob's bits = [0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1]
fidelity = 1.0
loss = 0.0
(.venv) qiskit$
• "eavedropping", 20 bits
  (.venv) qiskit$ python 5.2.py
Alice's bits are [1. 0. 1. 1. 1. 0. 1. 1. 1. 0. 1. 1. 0. 1. 1. 1. 0. 1. 0. 1.]
Alice's bases are [1. 0. 0. 0. 1. 0. 0. 1. 1. 0. 0. 1. 1. 1. 0. 0. 1. 0. 0. 0.]
Eve's bases are [0. 1. 0. 1. 1. 0. 1. 1. 1. 1. 1. 1. 0. 1. 0. 0. 1. 1. 0. 1.]
qiskit_runtime_service._discover_account:WARNING:2026-04-30 15:48:07,301: Loading account with the given token. A saved account will not be used.
ibm_marrakesh
Eve's measured = [1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 0]
Eve's bits are [1, 0, 1, 0, 1, 0, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 0]
Eve's bases are [0. 1. 0. 1. 1. 0. 1. 1. 1. 1. 1. 1. 0. 1. 0. 0. 1. 1. 0. 1.]
Bob's bases are [0. 1. 1. 1. 0. 1. 0. 0. 1. 1. 0. 0. 1. 0. 1. 1. 0. 1. 0. 0.]
Bob's measured = [1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 0, 1]
Alice's bits = [1, 1, 1, 0, 0, 1]
Bob's bits = [0, 1, 1, 1, 0, 1]
fidelity = 0.6666666666666666
loss = 0.33333333333333337
(.venv) qiskit$