Cryptographic protocols can be classified by the type of security against eavesdropping which they provide. There exist mathematically secure schemes whose security relies on mathematical proofs (like the Vernam cipher discussed below) or conjectures (like public key RSA encryption) about the complexity of deciphering the message without possessing the correct key. The majority of current secure public Internet connections rely on such schemes. Alternatively, a cryptographic setup may provide a physically secure method for communicating. In these setups the security is provided by the physical laws governing the communication protocol. Here we first discuss a provably secure classical communication protocol and then quantum methods for distributing the necessary keys. The BB84 protocol relies on the impossibility of perfectly distinguishing non-orthogonal quantum states from one copy of the quantum system. The scheme was invented in 1984 and is the first of its kind. In contrast, the Ekert91 protocol makes use of Bell correlations between entangled pairs of photons. These correlations are destroyed when Eve attempts to make a measurement on one of the particles but also when imperfections, such as decoherence processes, affect the scheme. As long as no such “elements of reality” are introduced, and Bell correlations violating local realism can be generated by Alice and Bob, no eavesdropper can be present. One-time pads and the Vernam cipher The Vernam cipher is a cryptographic protocol which allows the encryption and decryption protocol to be publicly known. The security of the protocol relies entirely on the key which is private and not publicly known. Alice and Bob share identical n -bit secret key strings (one-time pad).
Cryptographic protocols can be classified by the type of security against eavesdropping which they provide. There exist mathematically secure schemes whose security relies on mathematical proofs (like the Vernam cipher discussed below) or conjectures (like public key RSA encryption) about the complexity of deciphering the message without possessing the correct key. The majority of current secure public Internet connections rely on such schemes. Alternatively, a cryptographic setup may provide a physically secure method for communicating. In these setups the security is provided by the physical laws governing the communication protocol. Here we first discuss a provably secure classical communication protocol and then quantum methods for distributing the necessary keys. The BB84 protocol relies on the impossibility of perfectly distinguishing non-orthogonal quantum states from one copy of the quantum system. The scheme was invented in 1984 and is the first of its kind. In contrast, the Ekert91 protocol makes use of Bell correlations between entangled pairs of photons. These correlations are destroyed when Eve attempts to make a measurement on one of the particles but also when imperfections, such as decoherence processes, affect the scheme. As long as no such “elements of reality” are introduced, and Bell correlations violating local realism can be generated by Alice and Bob, no eavesdropper can be present. One-time pads and the Vernam cipher The Vernam cipher is a cryptographic protocol which allows the encryption and decryption protocol to be publicly known. The security of the protocol relies entirely on the key which is private and not publicly known. Alice and Bob share identical n -bit secret key strings (one-time pad).
Quantum cryptography is known the most up-to-date in domain of realistic cryptography notably the menace of quantum cryptanalysis which threatens security firmness of public key cryptography. Quantum cryptography has a famous scheme known as Quantum Key Exchange (QKE), that administrates generation and distribution of a secured random key between legitimate channel users depicted as sender and receiver. Consequently, such key could be used as a key for one-time pad hybrid cryptosystems to encrypt and authenticate messages over a quantum channel. (QKE) is based on unifying quantum physics concepts and information theory with conventional cryptographic schemes that target to produce a short secret session key between any two legitimate parties. An important phase in key creation of BB84 protocol is Privacy Amplification phase where two interconnecting parties distill highly secret shared key from a larger body of shared key, which is only partially secret. The two legitimate parties publicly exchange information to create a compressed key free from biased bits known by an eavesdropper.
Quantum cryptography is known the most up-to-date in domain of realistic cryptography notably the menace of quantum cryptanalysis which threatens security firmness of public key cryptography. Quantum cryptography has a famous scheme known as Quantum Key Exchange (QKE), that administrates generation and distribution of a secured random key between legitimate channel users depicted as sender and receiver. Consequently, such key could be used as a key for one-time pad hybrid cryptosystems to encrypt and authenticate messages over a quantum channel. (QKE) is based on unifying quantum physics concepts and information theory with conventional cryptographic schemes that target to produce a short secret session key between any two legitimate parties. An important phase in key creation of BB84 protocol is Privacy Amplification phase where two interconnecting parties distill highly secret shared key from a larger body of shared key, which is only partially secret. The two legitimate parties publicly exchange information to create a compressed key free from biased bits known by an eavesdropper.
Quantum Cryptography is based on the use of subatomic particles (photons) and their intrinsic quantum properties (photon polarization) to develop an unbreakable system. It is not possible to measure the quantum state of any system without affecting the system. This property provides secure transmission of key between sender and receiver. Quantum Cryptography is a way to combine the relative ease and convenience of key exchange in public key cryptography with the ultimate security of a one-time pad. Quantum techniques for key distribution, the classically impossible task of distributing secret information over an insecure channel whose transmissions are subject to inspection by an eavesdropper, between parties who share no secret key initially. Quantum Cryptography uses the principles of Quantum Mechanics to implement a cryptographic system. The key problem which is solved by using quantum techniques is that of eavesdropping detection. The bits are represented as qubits, physically modeled by photons, and communicated over a quantum channel. The polarization states of photons represent 0's and 1's. Keyword: Asymmetric key, Cryptography, Protocols, Quantum, symmetric key
Quantum cryptography is an emerging field that ensures secure communication by leveraging principles of quantum mechanics. Unlike classical cryptography methods that rely on mathematical complexity, quantum cryptographic protocols, Quantum Key Distribution (QKD) protocols derive their security from the fundamental laws of physics. Among these, the BB84 protocol is widely recognized for enabling secure key exchange between communicating parties, with any eavesdropping attempts being inherently detectable. The invention of quantum computing poses a significant threat to classical encryption algorithms, and thereby necessitating both post-quantum cryptography and quantum-based approaches. This paper presents a comprehensive overview of quantum cryptography, emphasizing its theoretical principles foundations of quantum cryptography, emphasizing its advantages over traditional encryption methods, implementation challenges, and real-world application. It also outlines the limitations of quantum technology, e.g., hardware limitations and interference by noise, which restrict large-scale application. A detailed comparison between classical, quantum, and hybrid cryptographic approaches is presented to highlight the key advancement, including improved eavesdropping detection, enhanced key generation rates, and security through quantum entanglement. As quantum networks evolve rapidly, quantum cryptography is poised to become a cornerstone of nextgeneration ultra-secure communication systems.
The practical implementation of quantum information technologies requires, for the most part, highly advanced and currently experimental procedures. One exception is quantum cryptography, or quantum key distribution, which has been successfully demonstrated in many laboratories and has reached an advanced level of development. It will probably become the first commercial application of quantum information. In quantum key distribution, Alice and Bob exploit a quantum channel to create a secret shared key comprising a random string of binary digits. This key can then be used to protect a subsequent communication between them. The principal idea is that the secrecy of the key distribution is ensured by the laws of quantum physics. Proving security for practical communication systems is a challenging problem and requires techniques that are beyond the scope of this book. At a fundamental level, however, the ideas are simple and may readily be understood with the knowledge we have already acquired. Quantum cryptography is the latest idea in the long history of secure (and not so secure) communications and, if it is to develop, it will have to compete with existing technologies. For this reason we begin with a brief survey of the history and current state of the art in secure communications before turning to the possibilities offered by quantum communications. The history of cryptography is a long and fascinating one. As a consequence of the success or, more spectacularly, the failure of ciphers, wars have been fought, battles decided, kingdoms won, and heads lost. In the information age, ciphers and cryptosystems have become part of everyday life; we use them to protect our computers, to shop over the Internet, and to access our money via an ATM (automated teller machine). One of the oldest and simplest of all ciphers is the transposition or Caesarean cipher (attributed to Julius Caesar), in which the letters are shifted by a known (and secret) number of places in the alphabet. If the shift is 1, for example, then A is enciphered as B, B→C, · · ·, Y→Z, Z→A. A shift of five places leads us to make the replacements A→F, B→G, · · ·, Y→D, Z→E.
Quantum cryptography using the BB84 protocol is at the forefront of modern secure communication. This paper emphasizes on BB84 protocol and its role in secure key distribution utilizing the Qiskit libraries in Python to simulate Quantum Key distribution (QKD). This QKD is then applied to the One-Time Pad algorithm for message encryption and decryption. Ensuring data confidentiality and integrity and is difficult due to advanced cyber threats and the potential of quantum computing to undermine traditional cryptographic methods. Current encryption techniques are susceptible to quantum related attacks, risking the decryption of sensitive data. Alice (sender) and Bob (receiver) use classical encryption to communicate but eavesdropper Eve with quantum capabilities, can potentially decrypt their messages. This vulnerability affects critical data security in finance, healthcare, and national security, making robust cryptographic solutions essential for maintaining trust and safety in digital communications. Our work emphasis the utilization of the quantum key generated by employing the BB84 protocol with the help of Qiskit library in python as cipher text in the process of one time pad encryption and decryption. This encrypted data dispatched between the sender and receiver to ensure maximum security, confidentiality and integrity over the period of communication.