Quantum Secure Algorithms

Quantum secure algorithms are cryptographic algorithms that are designed to be secure against the potential threats posed by quantum computers. Unlike classical cryptographic systems, which could be broken by quantum algorithms like Shor's algorithm, quantum secure algorithms leverage the principles of quantum mechanics to ensure security.

• **Quantum Key Distribution (QKD)**: A method for secure communication that uses quantum mechanics to securely share encryption keys.
• **Post-Quantum Cryptography (PQC)**: Cryptographic systems designed to be secure against quantum attacks, relying on mathematical problems that remain hard even for quantum computers.
• **Quantum Entanglement**: A phenomenon where particles become interconnected, influencing each other's states instantaneously, which is used in some quantum protocols.

Two significant quantum algorithms relevant to secure communications are:

1. BB84 Protocol: The first quantum key distribution protocol, developed by Charles Bennett and Gilles Brassard in 1984.
2. Quantum Digital Signatures: A method to provide authenticity and integrity to messages transmitted over a quantum channel.

Here’s a simple implementation example of a quantum key distribution protocol using Qiskit:

from qiskit import QuantumCircuit, Aer, transpile, assemble, execute

# BB84 Protocol Simulation
def bb84():
    qc = QuantumCircuit(2, 2)
    qc.h(0)  # Prepare a qubit in superposition
    qc.measure(0, 0)  # Measure the first qubit
    qc.measure(1, 1)  # Measure the second qubit
    
    # Simulate
    simulator = Aer.get_backend('qasm_simulator')
    compiled_circuit = transpile(qc, simulator)
    qobj = assemble(compiled_circuit)
    result = execute(qc, simulator).result()
    counts = result.get_counts(qc)
    return counts

print(bb84())