Secure Composition of Public Key Infrastructures and Protocols in Game-based Cryptographic Models

Vipul Goyal

Mordechai M. Yung

Investigating the capabilities of public key and related cryptographic techniques has recently become an important area of cryptographic research. In this paper we present some new algorithms and cryptographic protocols (Cryptoprotocols) which enlarge the range of applications of public key systems and enable us to perform certain transactions in communication networks. The basic cryptographic tools used are Rabm's Oblivious Transfer Protocol and an algorithm we developed for Number Embedding which is provably hard to invert. We introduce the protocol Subscription to a Public Key, which gives a way to transfer keys over insecure communication channels and has useful applications to cryptosystems. We develop the Secret Blocking Protocol, specified as follows 'A transfers a secret to B, B can block the message. If B does not block it, there is a probability P that he might get it. (1/2 ≤ P < 1, where we can control the size of P). A does not know if the message was blocked (but he can find out later)'. The classic cryptotransaction is the A1ental Poker Game. A cryptographically secure solution to the Multi Player Mental Poker Game is given. The approach used in constructing the solution provides a general methodology of provable and modular Protocol Composition.

Rudolf Sinaga, Frangky, Danang

Purpose – This study develops and empirically evaluates a Quantum Exposure Index (QEI) for characterizing quantum-related exposure observable from public-sector Transport Layer Security (TLS) infrastructures and supporting post-quantum migration prioritization. Methods – The framework integrates TLS protocol version, certificate public-key algorithm, classical key-strength equivalence, and Perfect Forward Secrecy into a normalized composite index. Component weights were derived through the Analytical Hierarchy Process, while non-intrusive TLS measurements from publicly accessible government infrastructures provided the empirical inputs. Sensitivity and sector-level analyses were conducted to examine the robustness and interpretability of the resulting exposure profiles. Findings – The evaluated infrastructures remain dependent on classical public-key cryptography and therefore retain exposure to future quantum-capable adversaries despite widespread adoption of modern TLS configurations and forward secrecy. The analysis further shows that cryptographic key strength and protocol configuration differentiate exposure profiles, whereas the continued reliance on quantum-vulnerable public-key primitives establishes a common exposure baseline. Classification outcomes are sensitive to interpretive thresholds, reinforcing the importance of continuous index values over categorical labels. Research Implications – The QEI provides a reproducible infrastructure-level baseline for prioritizing cryptographic inventories, monitoring migration progress, and supporting evidence-based post-quantum transition planning. Originality – This study combines operational TLS measurement, standardized cryptographic-strength mapping, and multicriteria weighting within a unified quantitative framework for assessing observable quantum exposure in public-sector infrastructures.

Vipul Goyal

Zvi Galil, Stuart Haber, Moti M. Yung

Sergey E. Yunakovsky, Maxim Kot, N. O. Pozhar +7 more

Abstract Quantum computing technologies pose a significant threat to the currently employed public-key cryptography protocols. In this paper, we discuss the impact of the quantum threat on public key infrastructures (PKIs), which are used as a part of security systems for protecting production environments. We analyze security issues of existing models with a focus on requirements for a fast transition to post-quantum solutions. Although our primary focus is on the attacks with quantum computing, we also discuss some security issues that are not directly related to the used cryptographic algorithms but are essential for the overall security of the PKI. We attempt to provide a set of security recommendations regarding the PKI from the viewpoints of attacks with quantum computers.