Lior Ozer | Searcharxiv

arXiv2025

A search for minute-time-scale flares from the transient AT\,2024wpp

The AT 2018cow-like fast blue optical transient AT2022tsd showed a large number of few-minute-duration, high-luminosity (~10^43 erg/s) flares. We present an intensive search for such flares from another 18cow-like event, AT2024wpp. We have used the Large Array Survey Telescope (LAST) to observe this transient between 28 and 74 days after the approximate time of zero flux. The target was observed for about 23 hours to a sensitivity that allows one to detect 3x10^42 erg/s flares at S/N>5. No optical flares have been found, suggesting a one-sided 2-sigma confidence upper limit of <0.02 on the flare's duty cycle, and flare rate lower than about 0.11/hr. These limits suggest that not all 18cow-like objects display a high rate of minute-timescale luminous flares. This can be explained either by diversity in the 18cow-like population or by viewing angle effects (e.g., beaming), or rather that the optical depth towards the central emitting region did not fall below unity during the particular search window.

astro-ph.HE↗

arXiv2023

Signatures From Pseudorandom States via $\bot$-PRFs

Different flavors of quantum pseudorandomness have proven useful for various cryptographic applications, with the compelling feature that these primitives are potentially weaker than post-quantum one-way functions. Ananth, Lin, and Yuen (2023) have shown that logarithmic pseudorandom states can be used to construct a pseudo-deterministic PRG: informally, for a fixed seed, the output is the same with $1-1/poly$ probability. In this work, we introduce new definitions for $\bot$-PRG and $\bot$-PRF. The correctness guarantees are that, for a fixed seed, except with negligible probability, the output is either the same (with probability $1-1/poly$) or recognizable abort, denoted $\bot$. Our approach admits a natural definition of multi-time PRG security, as well as the adaptive security of a PRF. We construct a $\bot$-PRG from any pseudo-deterministic PRG and, from that, a $\bot$-PRF. Even though most mini-crypt primitives, such as symmetric key encryption, commitments, MAC, and length-restricted one-time digital signatures, have been shown based on various quantum pseudorandomness assumptions, digital signatures remained elusive. Our main application is a (quantum) digital signature scheme with classical public keys and signatures, thereby addressing a previously unresolved question posed in Morimae and Yamakawa's work (Crypto, 2022). Additionally, we construct CPA secure public-key encryption with tamper-resilient quantum public keys.

cs.CR↗