Quantum Public-key Encryption Research Articles

Towards the Impossibility of Quantum Public Key Encryption with Classical Keys from One-Way Functions

There has been a recent interest in proposing quantum protocols whose security relies on weaker computational assumptions than their classical counterparts. Importantly to our work, it has been recently shown that public-key encryption (PKE) from one-way functions (OWF) is possible if we consider quantum public keys. Notice that we do not expect classical PKE from OWF given the impossibility results of Impagliazzo and Rudich (STOC'89). However, the distribution of quantum public keys is a challenging task. Therefore, the main question that motivates our work is if quantum PKE from OWF is possible if we have classical public keys. Such protocols are impossible if ciphertexts are also classical, given the impossibility result of Austrin et al.(CRYPTO'22) of quantum enhanced key-agreement (KA) with classical communication. In this paper, we focus on black-box separation for PKE with classical public key and quantum ciphertext from OWF under the polynomial compatibility conjecture, first introduced in Austrin et al.. More precisely, we show the separation when the decryption algorithm of the PKE does not query the OWF. We prove our result by extending the techniques of Austrin et al. and we show an attack for KA in an extended classical communication model where the last message in the protocol can be a quantum state.

A receipt-free quantum voting protocol based on quantum public key encryption and quantum key agreement

To better protect the privacy of voters, a receipt-free quantum voting protocol is first proposed, which adopts quantum key agreement and quantum public key encryption with single photons. We employ Lagrange interpolation polynomials and random numbers to blind the voting information on the bulletin board, so that it can minimize the public information. Furthermore, our receipt-free quantum voting protocol is information-theoretically secure, i.e., the eavesdropper cannot get any voting information by collecting both the quantum ciphertext and the public information. In addition, compared with the existing quantum voting protocols, our protocol can meet more security attributes, such as anonymity, unrepeatability, verifiability legitimacy and especially, receipt-freeness.

All-or-nothing oblivious transfer based on the quantum one-way function

Oblivious transfer (OT) is one of the keystones of secure multi-party computation. It is generally believed that unconditionally secure OT is impossible. In this article, we propose a practical and secure quantum all-or-nothing oblivious transfer protocol based on the quantum one-way function. The protocol is built upon a quantum public-key encryption construction, and its security relies on the no-cloning theorem and no-communication theorem. Practical security is reflected in limitations on non-demolition measurements.

Quantum public key encryption scheme with four states key

Asymmetric encryption has some important applications in the field of communication. In classical computers, most public key encryption schemes are designed based on computational assumption. In other words, they can ensure computational security. When the computing power is large enough, it will pose a threat to these encryption schemes. We propose a quantum public key encryption scheme which based on properties of quantum physics. Our scheme realizes encryption and decryption with few resources and does not rely on any computational assumption. The key in our scheme consists of classical bits and qubits. Where the private key are classical bit and public key are qubits. The public key are generated through private key. We analyze the performance and security of the scheme. Our scheme ensures the information-theoretic secure and can be implemented easily.

A secure quantum sealed-bid auction protocol based on quantum public key encryption

A secure quantum sealed-bid auction protocol based on quantum public key encryption

Quantum Election Protocol Based on Quantum Public Key Cryptosystem

There is no quantum election protocol that can fulfil the eight requirements of an electronic election protocol, i.e., completeness, robustness, privacy, legality, unreusability, fairness, verifiability, and receipt-freeness. To address this issue, we employ the general construction of quantum digital signature and quantum public key encryption, in conjunction with classic public key encryption, to develop and instantiate a general construction of quantum election protocol. The proposed protocol exhibits the following advantages: (i) no pre-shared key between any two participants is required, and no trusted third party or anonymous channels are required. The protocol is suitable for large-scale elections with numerous candidates and voters and accommodates the situation in which multiple voters vote simultaneously. (ii) It is the first protocol that dismantles the contradiction between verifiability and receipt-freeness in a quantum election protocol. It satisfies all eight requirements stated earlier under the physical assumptions that there exists a one-way untappable channel from the administrator to the voter and that there is no collusion between any of the three parties in the protocol. Compared with current election protocols with verifiability and receipt-freeness, this protocol relies upon fewer physical assumptions. (iii) This construction is flexible and can be instantiated into an election scheme having post-quantum security by applying cryptographic algorithms conveying post-quantum security. Moreover, utilizing quantum digital signature and public key encryption yields a good result: the transmitted ballots are in quantum states, so owing to the no-cloning theorem, ballot privacy is less likely to be compromised, even if private keys of the signature and public key encryption are leaked after the election. However, in existing election protocols employing classic digital signatures and public key encryption, ballot privacy can be easily violated if attackers obtain private keys. Thus, our construction enhances privacy.

Quantum public-key encryption schemes based on conjugate coding

We present several quantum public-key encryption (QPKE) protocols designed using conjugate coding single-photon strings; thus, they may be realized in the laboratory using current techniques. The first two schemes can encrypt one-bit messages; these are then extended to two kinds of QPKE schemes oriented toward multi-bit messages. In these schemes, Boolean functions are used as private keys and classical-quantum pairs as public keys, where one private key corresponds to an exponential number of public keys. Later, we discuss some issues related to authentication and a possible way to improve the security of the proposed schemes in this paper. The novel structure of the protocols presented here ensures that most of them are information-theoretic secure under attacks on the private key and on the encryption, while they can be realized more easily compared to other protocols.

Quantum Random Oracle Model for Quantum Public-Key Encryption

Random oracle model is a general security analysis tool for rigorous security proof and effective cryptographic protocol design. In the quantum world, the attempts of constructing a quantum random oracle (QRO) have been made, such as quantum-accessible random oracle for post-quantum cryptography and quantum random oracle for quantum digital signature. As in the classical circumstance, it is crucial and challenging to design and instantiate the QRO model with an appropriate quantum hash function. In this work, we construct a QRO model for quantum public-key encryption against key-collision attack, due to the near-orthogonality property of the QRO. To explore a feasible instantiation procedure in the quantum setting, we distinctively give two instantiation examples of QRO by means of single-qubit rotation and quantum fingerprinting, and compare the numerical results of their performances under the key-collision attack. As a result, we extend the QRO model to the security analysis of quantum public-key encryption beyond quantum digital signature, and immunity from collision-type attacks.

Bit-Oriented Quantum Public-Key Cryptosystem Based on Bell States

Quantum public key encryption system provides information confidentiality using quantum mechanics. This paper presents a quantum public key cryptosystem (QPKC) based on the Bell states. By Holevo’s theorem, the presented scheme provides the security of the secret key using one-wayness during the QPKC. While the QPKC scheme is information theoretic security under chosen plaintext attack (CPA). Finally some important features of presented QPKC scheme can be compared with other QPKC scheme.

Qubit-wise teleportation and its application in public-key secret communication

We propose a quantum public-key encryption (QPKE) protocol for an unknown multi-qubit state based on qubit-wise teleportation. The private-key is a computational Boolean function, whereas the public-key is a pair of a random bit string and a quantum state. A private-key corresponds to an exponential number of public-keys. Security analysis showed that the proposed protocol has information-theoretic security from attacks for the private-key and the encryption. A multi-partite quantum secret state sharing protocol is presented based on the proposed multi-qubit-oriented QPKE protocol. Such secret state sharing protocol is information-theoretically secure.

Bit-oriented quantum public-key encryption based on quantum perfect encryption

A bit-oriented quantum public-key encryption scheme is presented. We use Boolean functions as private-key and randomly changed pairs of quantum state and classical string as public-keys. Following the concept of quantum perfect encryption, we prepare the public-key with Hadamard transformation and Pauli transformation. The quantum part of public-keys is various with different classical strings. In contrast to the typical classical public-key scheme, one private-key in our scheme corresponds to an exponential number of public-keys. We investigate attack to the private-key and prove that the public-key is a totally mixed state. So the adversary cannot acquire any information about private-key from measurement of the public-key. Then, the attack to encryption is analyzed. Since the trace distance between two different ciphertexts is zero, the adversary cannot distinguish between the two ciphertext states and also obtains nothing about plaintext and private-key. Thus, we have the conclusion that the proposed scheme is information-theoretically secure under an attack of the private-key and encryption.

Bit-Oriented Quantum Public Key Probabilistic Encryption Schemes

Quantum public-key encryption system provides information confidentiality using quantum mechanics. In this paper, two bit-oriented public key probabilistic encryption schemes are constructed based on a new randomizing method combined with single-qubit rotation. They are strong enough to resist forward search attack and have private key secrecy. Moreover, the ciphertext expansion of the second scheme is low and the number of public key qubits used to encrypt is small under the condition that decryption error is negligible.

Public-key encryption and authentication of quantum information

Public-key cryptosystems for quantum messages are considered from two aspects: public-key encryption and public-key authentication. Firstly, we propose a general construction of quantum public-key encryption scheme, and then construct an information-theoretic secure instance. Then, we propose a quantum public-key authentication scheme, which can protect the integrity of quantum messages. This scheme can both encrypt and authenticate quantum messages. It is information-theoretic secure with regard to encryption, and the success probability of tampering decreases exponentially with the security parameter with regard to authentication. Compared with classical public-key cryptosystems, one private-key in our schemes corresponds to an exponential number of public-keys, and every quantum public-key used by the sender is an unknown quantum state to the sender.