Secure Messaging apps have seen growing adoption, and are used by billions of people daily. However, due to imminent threat of a "Harvest Now, Decrypt Later" attack, secure messaging providers must react know in order to make their protocols $\textit{hybrid-secure}$: at least as secure as before, but now also post-quantum (PQ) secure. Since many of these apps are internally based on the famous Signal's Double-Ratchet (DR) protocol, making Signal hybrid-secure is of great importance. In...

It is imperative to modernize traditional core cryptographic primitives, such as Oblivious Transfer (OT), to address the demands of the new digital era, where privacy-preserving computations are executed on low-power devices. This modernization is not merely an enhancement but a necessity to ensure security, efficiency, and continued relevance in an ever-evolving technological landscape. This work introduces two scalable OT schemes: (1) Helix OT, a $1$-out-of-$n$ OT, and (2) Priority OT,...

Internet of Medical Things (IoMT) has gained significant research focus in both academic and medical institutions. Nevertheless, the sensitive data involved in IoMT raises concerns regarding user validation and data privacy. To address these concerns, certificateless signcryption (CLSC) has emerged as a promising solution, offering authenticity, confidentiality, and unforgeability. Unfortunately, most existing CLSC schemes are impractical for IoMT due to their heavy computational and storage...

For decades now, mathematical complexity is being regarded as the sole means to creating a sufficient distance between a ciphertext and its generating plaintext. Alas, mathematical complexity operates under the irremovable shadow of stealth cryptanalysis. By its nature mathematical complexity is vulnerable to smarter mathematicians and better equipped adversaries, which is a sufficient motivation to explore an alternative means to project security. Applying the Innovation Solution Protocol...

We tackle the atypical challenge of supporting post-quantum cryptography (PQC) and its significant overhead in safety-critical vehicle-to-vehicle (V2V) communications, dealing with strict overhead and latency restrictions within the limited radio spectrum for V2V. For example, we show that the current use of spectrum to support signature verification in V2V makes it nearly impossible to adopt PQC. Accordingly, we propose a scheduling technique for message signing certificate transmissions...

We re-visit Unclonable Encryption as introduced by Gottesman in 2003. We look at the combination of Unclonable Encryption and Key Recycling, while aiming for low communication complexity and high rate. We introduce a qubit-based prepare-and-measure Unclonable Encryption scheme with re-usable keys. Our scheme consists of a single transmission by Alice and a single classical feedback bit from Bob. The transmission from Alice to Bob consists entirely of qubits. The rate, defined as the message...

Recent research in quantum cryptography has led to the development of schemes that encrypt and authenticate quantum messages with computational security. The security definitions used so far in the literature are asymptotic, game-based, and not known to be composable. We show how to define finite, composable, computational security for secure quantum message transmission. The new definitions do not involve any games or oracles, they are directly operational: a scheme is secure if it...

Although it is widely deemed impossible to overcome the information theoretic optimality of the one-time pad (OTP) cipher in pre and post-quantum cryptography, this work shows that the optimality of information theoretic security (ITS) of OTP is paradoxical from the perspective of information conservational computing and cryptography. To prove this point, ITS of OTP is extended to information conservational security (ICS) of scalable OTP (S-OTP) with percentage-based key extension where...

In the Wyner wiretap channel, a sender is connected to a receiver and an eavesdropper through two noisy channels. It has been shown that if the noise in the eavesdropper channel is higher than the receiver's channel, information theoretically secure communication from Alice to Bob, without requiring a shared key, is possible. The approach is particularly attractive noting the rise of quantum computers and possibility of the complete collapse of today's’ cryptographic infrastructure. If the...

Authenticated Key Exchange (AKE) is the backbone of internet security protocols such as TLS and IKE. A recent announcement by standardization bodies calling for a shift to quantum-resilient crypto has resulted in several AKE proposals from the research community. Because AKE can be generically constructed by combining a digital signature scheme with public key encryption (or a KEM), most of these proposals focused on optimizing the known KEMs and left the authentication part to the generic...

We consider the scenario where Alice wants to send a secret(classical) $n$-bit message to Bob using a classical key, and where only one-way transmission from Alice to Bob is possible. In this case, quantum communication cannot help to obtain perfect secrecy with key length smaller then $n$. We study the question of whether there might still be fundamental differences between the case where quantum as opposed to classical communication is used. In this direction, we show that there exist...