Create qkd.py

nexus_infinity_core/qkd.py

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+import numpy as np
+from scipy.linalg import expm
+from qiskit import QuantumCircuit, execute
+from qiskit.providers.aer import AerSimulator
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.kdf.hkdf import HKDF
+
+class QKD:
+    """
+    Quantum Key Distribution (QKD) for secure key exchange.
+
+    Attributes:
+    -----------
+    qen : QEN
+        Quantum Entanglement Network (QEN) instance.
+    alice_node : str
+        Alice's node identifier.
+    bob_node : str
+        Bob's node identifier.
+    shared_secret : str
+        Shared secret key.
+    """
+
+    def __init__(self, qen, alice_node, bob_node):
+        self.qen = qen
+        self.alice_node = alice_node
+        self.bob_node = bob_node
+        self.shared_secret = ''
+
+    def encode_qubit(self, bit):
+        """
+        Encode a classical bit onto a qubit.
+
+        Parameters:
+        -----------
+        bit : int
+            Classical bit (0 or 1).
+
+        Returns:
+        -------
+        qc : QuantumCircuit
+            Quantum circuit encoding the classical bit.
+        """
+        qc = QuantumCircuit(1)
+        if bit == 1:
+            qc.x(0)
+        return qc
+
+    def decode_qubit(self, qc):
+        """
+        Decode a qubit to retrieve the classical bit.
+
+        Parameters:
+        -----------
+        qc : QuantumCircuit
+            Quantum circuit encoding the qubit.
+
+        Returns:
+        -------
+        bit : int
+            Classical bit (0 or 1).
+        """
+        job = execute(qc, self.qen.simulator)
+        result = job.result()
+        measurement = result.get_counts()
+        bit = 0 if measurement['0'] > measurement['1'] else 1
+        return bit
+
+    def bb84_protocol(self):
+        """
+        Implement the BB84 protocol for QKD.
+
+        Returns:
+        -------
+        shared_secret : str
+            Shared secret key.
+        """
+        # Alice prepares and sends qubits to Bob
+        alice_bits = np.random.randint(2, size=256)  # 256-bit key
+        alice_qubits = [self.encode_qubit(bit) for bit in alice_bits]
+        self.qen.teleport_qubit(self.alice_node, self.bob_node, alice_qubits)
+
+        # Bob measures the qubits
+        bob_measurements = [self.decode_qubit(qc) for qc in alice_qubits]
+
+        # Alice and Bob publicly compare their bases
+        alice_bases = np.random.randint(2, size=256)  # 256-bit key
+        bob_bases = np.random.randint(2, size=256)  # 256-bit key
+        alice_bases_public = alice_bases.copy()
+        bob_bases_public = bob_bases.copy()
+
+        # Alice and Bob discard mismatched bases
+        alice_bits_filtered = [alice_bits[i] for i in range(256) if alice_bases[i] == bob_bases[i]]
+        bob_measurements_filtered = [bob_measurements[i] for i in range(256) if alice_bases[i] == bob_bases[i]]
+
+        # Alice and Bob generate the shared secret key
+        shared_secret = ''
+        for i in range(len(alice_bits_filtered)):
+            shared_secret += str(alice_bits_filtered[i] ^ bob_measurements_filtered[i])
+
+        self.shared_secret = shared_secret
+        return shared_secret
+
+    def hkdf_key_derivation(self, shared_secret):
+        """
+        Derive a cryptographic key from the shared secret using HKDF.
+
+        Parameters:
+        -----------
+        shared_secret : str
+            Shared secret key.
+
+        Returns:
+        -------
+        key : bytes
+            Derived cryptographic key.
+        """
+        salt = b'qkd-salt'
+        info = b'qkd-key-derivation'
+        hkdf = HKDF(
+            algorithm=hashes.SHA256(),
+            length=32,
+            salt=salt,
+            info=info
+        )
+        key = hkdf.derive(shared_secret.encode())
+        return key