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IEEE Conference of Russian Young Researchers in Electrical and Electronic Engineering

Post-Quantum Security of Messaging Protocols: Analysis of Double Ratcheting Algorithm

Julia Bobrysheva, Sergey Vladimirovich Zapechnikov

Published Jan 1, 2020• 6 citations
Publisher

Abstract

Development in the area of quantum technologies led to the appearance of first quantum computers. The threat of using a quantum computer for cryptanalysis requires wide implementing post-quantum security in computing algorithms and communication protocols. We evaluate the computational power of some existing quantum computers to illustrate the relevance of research in post-quantum security. One of the best ways to test post-quantum protocols is to embed them into some non-critical but widely-used sphere. Secure messaging is an excellent example of such an application. In the paper, we analyze the post-quantum security of well-known messaging specification Signal, which is considered to have high-security properties. The core of Signal specification is the Double Ratchet protocol. We notice and explain why it is not a post-quantum secure scheme. After that, we suggest some possible ways to improve the security features of Signal specification.

DOI
10.1109/eiconrus49466.2020.9039075

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Development in the area of quantum technologies led to the appearance of first quantum computers. The threat of using a quantum computer for cryptanalysis requires wide implementing post-quantum security in computing algorithms and communication protocols. We evaluate the computational power of some existing quantum computers to illustrate the relevance of research in post-quantum security. One of the best ways to test post-quantum protocols is to embed them into some non-critical but widely-used sphere. Secure messaging is an excellent example of such an application. In the paper, we analyze the post-quantum security of well-known messaging specification Signal, which is considered to have high-security properties. The core of Signal specification is the Double Ratchet protocol. We notice and explain why it is not a post-quantum secure scheme. After that, we suggest some possible ways to improve the security features of Signal specification.
Due to development in quantum computing, we need to create and implement new cryptographic protocols, which are resistant to attacks using a quantum computer, in all practical cases. Last years humans became using messengers to transfer far more important information than earlier, so it is necessary to create new post-quantum secure messaging protocols for peer-to-peer and group communications. In this article, we describe needed security properties, existing ways for the creation of group chats, and our suggestions. We described ways and needed primitives for the creation of a group key establishment scheme based on isogenies of elliptic curves. We describe such protocol as an extended Double Ratchet protocol.
Widely used communication and messaging protocols, e.g., TLS 1.3 and Signal, are insecure against an adversary with a quantum computer. We expect that post-quantum security will become mandatory for a new generation of cryptographic protocols in the nearest 10-15 years. The analysis of existing post-quantum secure cryptographic tools for key exchange, encryption and message authentication based on hard problems in codes, lattices, ring learning with errors and elliptic curve isogenies revealed their advantages and drawbacks. In particular, we conclude, that the main threat to communication and messaging protocols is only pre-quantum security of currently used Diffie-Hellman key exchange protocols. We summarize efficiency and safety results for each class of post-quantum cryptographic schemes and present an experimental implementation of isogeny-based Diffie-Hellman-like key exchange protocol as an illustration of their applicability.
Signal is a new security protocol and accompanying app that provides end-to-end encryption for instant messaging. The core protocol has recently been adopted by WhatsApp, Facebook Messenger, and Google Allo among many others, the first two of these have at least 1 billion active users. Signal includes several uncommon security properties (such as "future secrecy" or "post-compromise security"), enabled by a novel technique called ratcheting in which session keys are updated with every message sent. Despite its importance and novelty, there has been little to no academic analysis of the Signal protocol. We conduct the first security analysis of Signal's key agreement and double ratchet as a multi-stage key exchange protocol. We extract from the implementation a formal description of the abstract protocol, and define a security model which can capture the "ratcheting" key update structure. We then prove the security of Signal's core in our model, demonstrating several standard security properties. We have found no major flaws in the design, and hope that our presentation and results can serve as a starting point for other analyses of this widely adopted protocol.
Classical cryptographic primitives such as RSA or Diffie-Hellman key exchange are based on computationally difficult mathematical problems for the solution of which no efficient algorithms are known. However, with the advent of practical quantum computers, quantum algorithms can be used to easily solve these problems and break the security of these algorithms. For this reason, post-quantum algorithms are being rapidly developed, evaluated, and optimized to resist quantum attacks in the hope that they will be used in secure instant messaging protocols such as the Signal protocol, in addition to other secure network protocols. This literature review provides an overview of efforts to develop quantum-resistant primitives for secure instant messaging protocols, with a particular focus on the Signal protocol.
The Signal Protocol is a two-party secure messaging protocol used in applications such as Signal, WhatsApp, Google Messages and Facebook Messenger and is used by billions daily. It consists of two core components, one of which is the Double Ratchet protocol that has been the subject of a line of work that aims to understand and formalise exactly what security it provides. Existing models capture strong guarantees including resilience to state exposure in both forward security (protecting past secrets) and post-compromise security (restoring security), adaptive state corruptions, message injections and out-of-order message delivery. Due to this complexity, prior work has failed to provide security guarantees that do not degrade in the number of interactions, even in the single-session setting.
The rise of quantum computer made a significant threat to traditional cryptographic protocols which figured out the importance of implementing hybrid approaches which integrate classical and post quantum cryptographic techniques.In this overview, we analyze different areas where quantum computing technique is implemented and how it has contributed to those applications.Traditional encryption schemes like RSA and ECC can be attacked by quantum algorithm which necessitating the need for quantum resistant technique.The research includes the evaluation of different systems where the classical system are integrated with post quantum cryptographic algorithm.Besides, discuss and analyze the seamless working of existing network layer protocols with quantum algorithms.This survey provides a foundation for protecting systems from upcoming quantum threats, which describes the advancements in post-quantum algorithms and quantum cryptography.