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Quantum bit commitment (QBC) is a quantum version of the classical bit commitment security primitive. As other quantum security primitives and protocols, QBC improves on cheating detection over its classical counterpart. The implementation of the QBC protocol below relies on the use of common quantum gates: the Hadamard gate used for orthonormal bases and the CNOT gate used to swap qubits. The protocol was run and tested on IBM quantum experience (IBM QX). IBM QX offers two different quantum environments: as a simulator and as a real quantum machine. In our implementation, honest and dishonest participants were considered. Results of both the simulation and the quantum execution were compared against the theoretical expectations. The IBM QX simulator gives results that match the theoretical model. The IBM QX real computer deviates from the expected behavior by a measurable amount. Using the standard deviation and the Hamming distance, the conclusion is that the quantum computer is usable as the difference to the simulator is within an acceptable margin of error. The QBC protocol of choice is fully secure against cheating by Bob. The only way Alice can cheat is using multi-dimensional entanglement. The cost for Alice to cheat is exponential in the number of qubits used, namely O (2 6 n + 3 k + 1) . [ABSTRACT FROM AUTHOR]

Together with bit commitment, Oblivious Transfer is a very useful cryptographic primitive with important applications, most notably in secure multiparty computations. It has been long known that secure Quantum Oblivious Transfer can be achieved from a secure implementation of Quantum Bit Commitment. Unfortunately, it is also well known that unconditionally secure Quantum Bit Commitment is impossible, so building a secure Oblivious Transfer protocol on top of Quantum Bit Commitment is ruled out. In this paper, we propose a relatively simple quantum protocol for Oblivious Transfer which does not require qubit storage, does not rely on bit commitment as a primitive and is easily implementable with current technology, if the two actors are honest. The protocol is proven to be secure against any individual measurements and entanglement-based attacks. Any cheating attempt trying to speculate collective measurements would be considerably difficult to put in practice, even in the near future. Furthermore, the number of qubits used in our scheme (embodied as photons in a physical realization of the protocol) acts as a security parameter, making it increasingly hard to cheat. [ABSTRACT FROM AUTHOR]

Quantum bit commitment (QBC) is a fundamental cryptographic primitive that can be used as a building block for a whole set of applications like remote coin tossing, zero-knowledge proofs or secure two-party computation. Unconditionally secure QBC, that is a protocol which is both fully binding and fully concealing, is deemed impossible due to the use of entanglement by a dishonest participant [10, 14]. In this paper, we describe a protocol that implements QBC using quantum memories, meaning that a qubit can be stored for as long as needed. We prove that, in the absence of entanglement, our protocol exhibits both properties: it is both binding and concealing. Its security exploits the algebraic properties of an equivalence class with two types of operators: permutation and the Hadamard transform. The only theoretical attack that can be mounted concerns the binding property through the use of entanglement and the Schmidt decomposition. However, for all practical purposes, such an attack can be made arbitrarily difficult, by increasing the value of a security parameter, namely the number of qubits used in the protocol. [ABSTRACT FROM AUTHOR]

Current quantum cryptographic protocols aim to distribute a classical secret key to be used afterwards in classical encryption/decryption schemes. We show in this paper that quantum information processing can be used to do much more than just key distribution. Simple quantum transformations augmented with the ability to store qubits in a quantum memory are the building blocks of a class of protocols allowing two parties to communicate secretly by encoding/decoding the exchanged message directly through quantum means, without the need to establish a secret encryption/decryption key first. Consequently, our quantum mechanical process of securely transmitting a message through a public channel is conceptually simpler than the two-step scenario with a quantum distributed classical key. In addition, since the encrypted message is only transmitted through a quantum channel, copying and off-line analysis of the transmission is impossible. Our algorithms rely on the common assumption that public information can be authenticated. In terms of security, the protocol using three encoding bases achieves the maximum detection rate of 33 % per qubit tested. The probability of catching a potential eavesdropper can be brought as close to 1 as desired by increasing the length of the signature string attached to the message. [ABSTRACT FROM AUTHOR]

It has been said that quantum cryptography in general offers a secure solution to the problem of key enhancement. This means that two parties who already share a small secret key, can use quantum protocols to establish a new large secret key. This large secret key can be arbitrarily long and is unbreakable. Thus, to date, the main contribution of quantum cryptography has been believed to be quantum key enhancement. This paper shows that quantum cryptography can do significantly more. The quantum protocol described here distributes an unbreakable secret key to the two parties by relying on public information only. This is the first time that quantum cryptography is shown to be able to produce secret information using only public information. This contribution is also unique for cryptography in general, classical and quantum. [ABSTRACT FROM AUTHOR]

The identity theft problem, an ever growing threat to safety and security in today's society, is very difficult to tackle using classical means, due to the fact that classical information can be easily read and copied. In this paper, we show that we can do more than it is possible classically through the use of specific tools and techniques from quantum information processing and quantum cryptography. Specifically, we devise a quantum security scheme that completely eliminates the problem of identity theft in sensor networks, although our scheme may be of interest in more general situations involving secrecy and authentication. The hypercomputational aspect of this result pertains to the unprecedented level of security achieved, a level that is beyond the reach of classical information processing. [ABSTRACT FROM AUTHOR]