596 research outputs found
Breaking Symmetric Cryptosystems Using Quantum Period Finding
Due to Shor's algorithm, quantum computers are a severe threat for public key
cryptography. This motivated the cryptographic community to search for
quantum-safe solutions. On the other hand, the impact of quantum computing on
secret key cryptography is much less understood. In this paper, we consider
attacks where an adversary can query an oracle implementing a cryptographic
primitive in a quantum superposition of different states. This model gives a
lot of power to the adversary, but recent results show that it is nonetheless
possible to build secure cryptosystems in it.
We study applications of a quantum procedure called Simon's algorithm (the
simplest quantum period finding algorithm) in order to attack symmetric
cryptosystems in this model. Following previous works in this direction, we
show that several classical attacks based on finding collisions can be
dramatically sped up using Simon's algorithm: finding a collision requires
queries in the classical setting, but when collisions happen
with some hidden periodicity, they can be found with only queries in the
quantum model.
We obtain attacks with very strong implications. First, we show that the most
widely used modes of operation for authentication and authenticated encryption
e.g. CBC-MAC, PMAC, GMAC, GCM, and OCB) are completely broken in this security
model. Our attacks are also applicable to many CAESAR candidates: CLOC, AEZ,
COPA, OTR, POET, OMD, and Minalpher. This is quite surprising compared to the
situation with encryption modes: Anand et al. show that standard modes are
secure with a quantum-secure PRF.
Second, we show that Simon's algorithm can also be applied to slide attacks,
leading to an exponential speed-up of a classical symmetric cryptanalysis
technique in the quantum model.Comment: 31 pages, 14 figure
Quantum Algorithms for Some Hidden Shift Problems
Almost all of the most successful quantum algorithms discovered to date exploit the ability of the Fourier transform to recover subgroup structures of functions, especially periodicity. The fact that Fourier transforms can also be used to capture shift structure has received far less attention in the context of quantum computation. In this paper, we present three examples of "unknown shift" problems that can be solved efficiently on a quantum computer using the quantum Fourier transform. For one of these problems, the shifted Legendre symbol problem, we give evidence that the problem is hard to solve classically, by showing a reduction from breaking algebraically homomorphic cryptosystems. We also define the hidden coset problem, which generalizes the hidden shift problem and the hidden subgroup problem. This framework provides a unified way of viewing the ability of the Fourier transform to capture subgroup and shift structure
Cloud Computing in the Quantum Era
Cloud computing has become the prominent technology of this era. Its elasticity, dynamicity, availability, heterogeneity, and pay as you go pricing model has attracted several companies to migrate their businesses' services into the cloud. This gives them more time to focus solely on their businesses and reduces the management and backup overhead leveraging the flexibility of cloud computing. On the other hand, quantum technology is developing very rapidly. Experts are expecting to get an efficient quantum computer within the next decade. This has a significant impact on several sciences including cryptography, medical research, and other fields. This paper analyses the reciprocal impact of quantum technology on cloud computing and vice versa
Using Simon's Algorithm to Attack Symmetric-Key Cryptographic Primitives
We present new connections between quantum information and the field of
classical cryptography. In particular, we provide examples where Simon's
algorithm can be used to show insecurity of commonly used cryptographic
symmetric-key primitives. Specifically, these examples consist of a quantum
distinguisher for the 3-round Feistel network and a forgery attack on CBC-MAC
which forges a tag for a chosen-prefix message querying only other messages (of
the same length). We assume that an adversary has quantum-oracle access to the
respective classical primitives. Similar results have been achieved recently in
independent work by Kaplan et al. Our findings shed new light on the
post-quantum security of cryptographic schemes and underline that classical
security proofs of cryptographic constructions need to be revisited in light of
quantum attackers.Comment: 14 pages, 2 figures. v3: final polished version, more formal
definitions adde
Using quantum key distribution for cryptographic purposes: a survey
The appealing feature of quantum key distribution (QKD), from a cryptographic
viewpoint, is the ability to prove the information-theoretic security (ITS) of
the established keys. As a key establishment primitive, QKD however does not
provide a standalone security service in its own: the secret keys established
by QKD are in general then used by a subsequent cryptographic applications for
which the requirements, the context of use and the security properties can
vary. It is therefore important, in the perspective of integrating QKD in
security infrastructures, to analyze how QKD can be combined with other
cryptographic primitives. The purpose of this survey article, which is mostly
centered on European research results, is to contribute to such an analysis. We
first review and compare the properties of the existing key establishment
techniques, QKD being one of them. We then study more specifically two generic
scenarios related to the practical use of QKD in cryptographic infrastructures:
1) using QKD as a key renewal technique for a symmetric cipher over a
point-to-point link; 2) using QKD in a network containing many users with the
objective of offering any-to-any key establishment service. We discuss the
constraints as well as the potential interest of using QKD in these contexts.
We finally give an overview of challenges relative to the development of QKD
technology that also constitute potential avenues for cryptographic research.Comment: Revised version of the SECOQC White Paper. Published in the special
issue on QKD of TCS, Theoretical Computer Science (2014), pp. 62-8
Quantum Attacks on Modern Cryptography and Post-Quantum Cryptosystems
Cryptography is a critical technology in the modern computing industry, but the security of many cryptosystems relies on the difficulty of mathematical problems such as integer factorization and discrete logarithms. Large quantum computers can solve these problems efficiently, enabling the effective cryptanalysis of many common cryptosystems using such algorithms as Shor’s and Grover’s. If data integrity and security are to be preserved in the future, the algorithms that are vulnerable to quantum cryptanalytic techniques must be phased out in favor of quantum-proof cryptosystems. While quantum computer technology is still developing and is not yet capable of breaking commercial encryption, these steps can be taken immediately to ensure that the impending development of large quantum computers does not compromise sensitive data
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