Papers updated in last 31 days (Page 4 of 302 results)

Last updated:  2022-10-31
Lattice-Based Quantum Advantage from Rotated Measurements
Yusuf Alnawakhtha, Atul Mantri, Carl A. Miller, and Daochen Wang
Trapdoor claw-free functions (TCFs) are immensely valuable in cryptographic interactions between a classical client and a quantum server. Typically, a protocol has the quantum server prepare a superposition of two-bit strings of a claw and then measure it using Pauli-$X$ or $Z$ measurements. In this paper, we demonstrate a new technique that uses the entire range of qubit measurements from the $XY$-plane. We show the advantage of this approach in two applications. First, building on (Brakerski et al. 2018, Kalai et al. 2022), we show an optimized two-round proof of quantumness whose security can be expressed directly in terms of the hardness of the LWE (learning with errors) problem. Second, we construct a one-round protocol for blind remote preparation of an arbitrary state on the $XY$-plane up to a Pauli-$Z$ correction.
Last updated:  2022-10-31
Big Brother Is Watching You: A Closer Look At Backdoor Construction
Anubhab Baksi, Arghya Bhattacharjee, Jakub Breier, Takanori Isobe, and Mridul Nandi
With the advent of Malicious (Peyrin and Wang, Crypto'20), the question of a cipher with an intentional weakness which is only known to its designer has gained its momentum. In their work, the authors discuss how an otherwise secure cipher can be broken by its designer with the help of a secret backdoor (which is not known to the user/attacker). The contribution of Malicious is to propose a cipher-level construction with a backdoor, where it is computationally infeasible to retrieve the backdoor entry despite knowing how the mechanism works. In this work, we revisit the work done by Peyrin and Wang in a greater depth. We discuss the relevant aspects with more clarity, thereby addressing some of the important issues connected to a backdoor construction. The main contribution, however, comes as a new proof-of-concept block cipher with an innate backdoor, named ZUGZWANG. Unlike Malicious, which needs new/experimental concepts like partially non-linear layer; our cipher entirely relies on concepts which are well-established for decades (such as, using a one-way function as a Feistel cipher's state-update), and also offers quite a few advantages over Malicious (easy to visualise, succeeds with probability 1, and so on). Having known the secret backdoor entry, one can recover the secret key with only 1 plaintext query to our cipher; but it is secure otherwise. As the icing on the cake, we show the provable security claims for our cipher.
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