Multi-key Authenticated Encryption with Corruptions: Reductions Are Lossy

Tibor Jager, Martijn Stam, Ryan Stanley-Oakes, Bogdan Warinschi

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

3 Citations (Scopus)


We study the security of symmetric encryption schemes in settings with multiple users and realistic adversaries who can adaptively corrupt encryption keys. To avoid confinement to any particular definitional paradigm, we propose a general framework for multi-key security definitions. By appropriate settings of the parameters of the framework, we obtain multi-key variants of many of the existing single-key security notions.

This framework is instrumental in establishing our main results. We show that for all single-key secure encryption schemes satisfying a minimal key uniqueness assumption and almost any instantiation of our general multi-key security notion, any reasonable reduction from the multi-key game to a standard single-key game necessarily incurs a linear loss in the number of keys. We prove this result for all three classical single-key security notions capturing confidentiality, authenticity and the combined authenticated encryption notion.
Original languageEnglish
Title of host publicationTheory of Cryptography
Subtitle of host publication15th International Conference, TCC 2017, Baltimore, MD, USA, November 12-15, 2017, Proceedings, Part I
Number of pages33
ISBN (Electronic)9783319705002
ISBN (Print)9783319704999
Publication statusPublished - 5 Nov 2017

Publication series

NameLecture Notes in Computer Science
PublisherSpringer Berlin Heidelberg
ISSN (Print)0302-9743


  • Secret-key cryptography/authenticated encryption
  • Multi-user security
  • Multi-key security
  • Black-box reductions

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