It is well known that Shor's quantum algorithm for integer factorization can break down the RSA public-key cryptosystem, which is widely used in many cryptographic applications. Thus, public-key cryptosystems in the quantum computational setting are longed for cryptology. In order to define the security notions of public-key cryptosystems, we have to model the power of the sender, receiver, adversary and channel. While we may consider a setting where quantum computers are available only to adversaries, we generally discuss what are the right security notions for (quantum) public-key cryptosystems in the quantum computational setting. Moreover, we consider the security of quantum public-key cryptosystems known so far.
It is well known that Shor's quantum algorithm for integer factorization can break down the RSA public-key cryptosystem, which is widely used in many cryptographic applications. Thus, public-key cryptosystems in the quantum computational setting are longed for cryptology. In order to define the security notions of public-key cryptosystems, we have to model the power of the sender, receiver, adversary and channel. While we may consider a setting where quantum computers are available only to adversaries, we generally discuss what are the right security notions for (quantum) public-key cryptosystems in the quantum computational setting. Moreover, we consider the security of quantum public-key cryptosystems known so far.
Abstract. This paper presents a new paradigm of cryptography, quantum public-key cryptosystems. In quantum public-key cryptosystems, all parties including senders, receivers and adversaries are modeled as quantum (probabilistic) poly-time Turing (QPT) machines and only classical channels (i.e., no quantum channels) are employed. A quantum trapdoor one-way function, f, plays an essential role in our system, in which a QPT machine can compute f with high probability, any QPT machine can invert f with negligible probability, and a QPT machine with trapdoor data can invert f. This paper proposes a concrete scheme for quantum public-key cryptosystems: a quantum public-key encryption scheme or quantum trapdoor one-way function. The security of our schemes is based on the computational assumption (over QPT machines) that a class of subset-sum problems is intractable against any QPT machine. Our scheme is very efficient and practical if Shor’s discrete logarithm algorithm is efficiently realized on a quantum machine.
Compared with electronic computers, quantum parallelism has led to a significant increase in the computing power of quantum computers.However, the computing power of quantum computers will also be limited by the laws of physics, and hence there is no doubt that the computing power of quantum computers is not unlimited.For an algorithm, we need to consider both its space complexity and time complexity.This not only requires quantum computers to achieve large-scale integration, but also requires the quantum coherence time to be sufficiently long.If either of the above two conditions is not met, the task cannot be completed.Shor's algorithm [1] reduced the computational complexity of large integer factorization to the polynomial level.This complexity is of the same order as that of the encryption and decryption for the RSA public key cryptography protocol, which leads to the insecurity of the RSA in universal quantum computing.In addition, some other quantum algorithms show different kinds of enhanced speeds for solving different problems, such as the Grover's search algorithm [2] and its improved works [ 3 , 4 ], and the HHL algorithm [5] .With the remarkable computational power of these quantum algorithms, physicists have begun to seek suitable physical systems for the implementation of quantum computing.The implementation of quantum computing includes several basic technologies, such as preparation, precise control, measurement of the physical qubits, and construction of logical qubits.At present, there are many experimental candidate quantum computing platforms, including the superconducting system [6] , trapped ions system [7] , nitrogenvacancy centers in diamonds [8] , and ultra-cold atoms [9] .Recently, Google experimentally demonstrated quantum supremacy with a superconducting quantum computer [10] , thus placing the research on quantum computing at the forefront.With the booming development of quantum computing technology, the public key cryptosystem also needs to be updated periodically.Thus, cryptographers have to constantly look for public key protocols to resist quantum computing attacks, which leads to the emergence of postquantum cryptography.It is worth noting that although the name of post-quantum cryptography contains the word 'quantum', it essentially consists of protocols of classical cryptography.The current research on post-quantum cryptography mainly includes protocols based on the following four frameworks: the protocols based on Hash function, the pro- * Corresponding author.
With recent advances on the capabilities of quantum computers and the seminal work by Shor on the prime factorization of integers with quantum algorithms, the threat of quantum computers is looming over public-key based cryptographic systems. Two distinct areas of research – post-quantum and quantum cryptography – provide the technical means to secure cryptographic systems against potentially powerful enough quantum computers. As both technologies are now becoming readily available, integration in a wide range of applications to understand their characteristics and trade-offs and the associated evaluation is of importance.
The aim of this thesis is to study quantum computers and their impact on public-key cryptography. Crucial part of the work is dedicated to theoretical basis and definitions necessary for understanding the basic principles of quantum computers. The further chapters describe Shor's algorithm, explain the part of integer factoring problem in the security of current public key cryptographic algorithms, and show how to break the most widely used assymetric algorithm RSA by means of effective factoring. Last chapter provides comparison of classical factoring algorithms with Shors algorithm, mentions cryptography resistant to quantum computer attacks and discusses the current state of development in the field of qunatum computing. The conclusion summarizes both potential and real impact of quantum computers on public-key cryptography.
The ongoing development of Quantum Computing (QC) is a breakthrough paradigm that holds the power to revolutionize the way we process information and solve complex problems today. Quantum Computation works on the fundamental principles of Superposition and Entanglement, enabling Quantum Computers to Leverage the power of Physics in Computing. QC has the potential to revolutionize fields such as Drug Development, Financial Modeling, Optimization, and Cryptography. Shor’s algorithm, a quantum algorithm used to factorize large numbers, poses significant threats to RSA, a widely used public key cryptosystem. RSA relies on the difficulty of factoring large semi-primes to keep its security. Shor's algorithm's ability to factorize quickly on a quantum computer undermines RSA's security assumptions, necessitating the exploration of post-quantum cryptographic solutions to ensure secure communication in the quantum era. The goal of this paper is to assess the present state of Shor's algorithm implementation and efficiency, specifically its application in the context of compromising public key cryptosystems like RSA.
Public-key cryptography is a key technology for making the Internet and other IT infrastructures secure. The security of the established public-key cryptosystems relies on the difficulty of factoring large composite integers or computing discrete logarithms. However, it is unclear whether these computational problems remain intractable in the future. For example, Shor showed in 1994 that quantum computers can be used to factor integers and to compute discrete logarithms in polynomial time. It is therefore necessary to develop alternative public-key cryptosystems which do not rely on the difficulty of factoring or computing discrete logarithms and which are secure even against quantum computer attacks. We call such cryptosystems quantum-immune. To prove the security of these quantum-immune cryptosystems, appropriate security models have to be used. Since quantum computers are able to solve problems in polynomial time which are supposed to be intractable for classical computers, the existing security models are inadequate in the presence of quantum adversaries. Therefore, new security models have to be developed to capture quantum adversaries. Properties of these new security models have to be investigated. On a more practical level, the quantum-immune cryptosystems have to be implemented in a way that they can seamlessly replace established cryptosystems. The implementations have to be efficient and suitable for resource-constrained devices. They must easily integrate into existing public-key infrastructures. This thesis contributes to both the theory and practice of quantum-immune cryptography, addressing the above-mentioned challenges. In the theoretical part, we concentrate on the quantum zero-knowledge property of interactive proof systems. We show for the first time that the quantum statistical, perfect, and computational zero-knowledge properties are preserved under sequential composition of interactive proof systems. In the practical part, we provide implementations of the most important quantum-immune cryptosystems. We present efficiency improvements of some of the alternative cryptosystems. The implementations are very efficient and easily integrate into existing public-key infrastructures. We present comprehensive timings that show that the alternative cryptosystems are competitive or even superior compared to established cryptosystems. Finally, we present a new cryptographic API that is particularly well-suited for resource-constrained devices like mobile phones and PDAs. With this API, the alternative cryptosystems can also be used with these devices.