Public-channel cryptography

Margaret B. Cozzens, Steven Miller

S. Rajasekar, R. Velusamy

Quantum cryptography lies at the intersection of information theory and quantum mechanics. Cryptosystems come in two major classes depending on whether the key is shared in public or in secret. Public key cryptosystems are special in that they allow two people, who have not yet met, to communicate securely by looking-up encryption methods in a public directory. In quantum cryptography, the sender and receiver have two types of communication channels: a classical public channel and a quantum channel. The best application of cryptography is to allow a secure communication. In the near future, quantum cryptography may be used in top-secret applications in the military, for example, as the basis of communication links. The first protocol for quantum cryptography was proposed in 1984 by C. H. Bennett and G. Brassard. Some of the basic quantum cryptographic systems are: four-states protocol, two-states protocol, 4+2 protocol and multi-photon and multi-stage protocol.

Yuh‐Min Tseng, Ting-Chieh Ho, Sen‐Shan Huang +1 more

In public-key cryptography (PKC), a signcryption (SC) scheme is a significant primitive by combining both signature and encryption functionalities in one scheme while reducing computing time. Most SC schemes are based on single PKC setting, such as public-key infrastructure PKC (PKI-PKC), identity-based PKC (ID-PKC), certificate-based PKC (CB-PKC), and certificateless PKC (CL-PKC). For providing practical usage, numerous hybrid SC (HSC) schemes were also presented to suit for the sense that a sender and a recipient belong to different PKC settings (i.e., heterogeneous PKC settings). Recently, side-channel attacks have been realized to endanger the existing SC and HSC schemes. Indeed, the research of leakage-resilient cryptography resistant to side-channel attacks have attracted the attention of researchers. Indeed, several SC schemes with leakage resilience (SC-LR) based on single PKC setting have been proposed. However, little research focuses on HSC scheme with leakage-resilience (HSC-LR). Therefore, this paper aims to design the first HSC-LR from senders under a CB-PKC setting to recipients under a PKI-PKC setting, called as the HSC-LR-CBPKI scheme. We formally define a new framework and two security games of the HSC-LR-CBPKI scheme. Two security theorems are proved that the HSC-LR-CBPKI scheme possesses both signature and encryption functionalities (including unforgeability and confidentiality) under side-channel attacks. Finally, the proposed scheme is very efficient by performance analysis.

Sanjam Garg, Yuval Ishai, Eyal Kushilevitz Z +2 more

Oded Goldreich

Trey Li

Secure quantum communication traditionally assumes that the adversary controls only the public channel. We consider a more powerful adversary who can demand private information of users. This type of adversary has been studied in public key cryptography in recent years, initiated by Persiano, Phan, and Yung at Eurocrypt 2022. We introduce a similar attacker to quantum communication, referring to it as the controller. The controller is a quantum computer that controls the entire communication infrastructure, including both classical and quantum channels. It can even ban classical public key cryptography and post-quantum public key cryptography, leaving only quantum cryptography and post-quantum symmetric key cryptography as the remaining options. We demonstrate how such a controller can control quantum communication and how users can achieve covert communication under its control.