Keyless secrecy against bounded adversaries

Quantum Physics arXiv:2609.12251 (quant-ph) [Submitted on 10 Sep 2026] Title:Keyless secrecy against bounded adversaries Authors:Anne Broadbent, Upendra Kapshikar, Denis Rochette View a PDF of the paper titled Keyless secrecy against bounded adversaries, by Anne Broadbent and 1 other authors View PDF HTML (experimental) Abstract:We introduce a keyless coding/cryptographic primitive that asks for two guarantees at once: the receiver is never fooled into accepting a message other than the one sent, and the adversary learns nothing about the message unless the receiver aborts. Neither the sender nor the receiver holds a secret key, and no computational hardness is assumed. The only restriction is on the adversary's online computation: the receiver aborts if nothing arrives by a fixed deadline, so the adversary must forward something before it, and her map in that window is computed by a circuit of size (or depth) at most $p$; before and after, she is unbounded. For every polynomial $p$ we construct such an efficient quantum scheme, encoding $k$-bit messages into $n = O(k)$ qubits with circuits of size $\mathrm{poly}(n,p)$. No classical scheme achieves this type of everlasting security, at any choice of parameters. Our techniques also resolve open questions about universal tamper detection against families restricted in cardinality rather than in circuit size. We settle a question of Broadbent, Kapshikar and Rochette on relaxed tamper detection. As a corollary, we obtain the first efficient non-malleable code secure against global quantum tampering, with no split-state restriction, whereas the current constructions in the literature require the codeword to be split into non-communicating shares. Subjects: Quantum Physics (quant-ph) Cite as: arXiv:2609.12251 [quant-ph] (or arXiv:2609.12251v1 [quant-ph] for this version) https://doi.org/10.48550/arXiv.2609.12251 Focus to learn more arXiv-issued DOI via DataCite (pending registration) Submission history From: Denis Rochette [view email] [v1] Thu, 10 Sep 2026 22:17:06 UTC (52 KB) Full-text links: Access Paper: View a PDF of the paper titled Keyless secrecy against bounded adversaries, by Anne Broadbent and 1 other authorsView PDFHTML (experimental)TeX Source view license Current browse context: quant-ph new | recent | 2026-09 References & Citations INSPIRE HEP NASA ADSGoogle Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... Data provided by: Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Code, Data and Media Associated with this Article alphaXiv Toggle alphaXiv (What is alphaXiv?) Links to Code Toggle CatalyzeX Code Finder for Papers (What is CatalyzeX?) DagsHub Toggle DagsHub (What is DagsHub?) GotitPub Toggle Gotit.pub (What is GotitPub?) Huggingface Toggle Hugging Face (What is Huggingface?) ScienceCast Toggle ScienceCast (What is ScienceCast?) Demos Demos Replicate Toggle Replicate (What is Replicate?) Spaces Toggle Hugging Face Spaces (What is Spaces?) Spaces Toggle TXYZ.AI (What is TXYZ.AI?) Related Papers Recommenders and Search Tools Link to Influence Flower Influence Flower (What are Influence Flowers?) Core recommender toggle CORE Recommender (What is CORE?) Author Venue Institution Topic About arXivLabs arXivLabs: experimental projects with community collaborators arXivLabs is a framework that allows collaborators to develop and share new arXiv features directly on our website. Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them. Have an idea for a project that will add value for arXiv's community? Learn more about arXivLabs. Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)