---
_id: '6430'
abstract:
- lang: eng
  text: "A proxy re-encryption (PRE) scheme is a public-key encryption scheme that
    allows the holder of a key pk to derive a re-encryption key for any other key
    \U0001D45D\U0001D458′. This re-encryption key lets anyone transform ciphertexts
    under pk into ciphertexts under \U0001D45D\U0001D458′ without having to know the
    underlying message, while transformations from \U0001D45D\U0001D458′ to pk should
    not be possible (unidirectional). Security is defined in a multi-user setting
    against an adversary that gets the users’ public keys and can ask for re-encryption
    keys and can corrupt users by requesting their secret keys. Any ciphertext that
    the adversary cannot trivially decrypt given the obtained secret and re-encryption
    keys should be secure.\r\n\r\nAll existing security proofs for PRE only show selective
    security, where the adversary must first declare the users it wants to corrupt.
    This can be lifted to more meaningful adaptive security by guessing the set of
    corrupted users among the n users, which loses a factor exponential in  Open image
    in new window , rendering the result meaningless already for moderate Open image
    in new window .\r\n\r\nJafargholi et al. (CRYPTO’17) proposed a framework that
    in some cases allows to give adaptive security proofs for schemes which were previously
    only known to be selectively secure, while avoiding the exponential loss that
    results from guessing the adaptive choices made by an adversary. We apply their
    framework to PREs that satisfy some natural additional properties. Concretely,
    we give a more fine-grained reduction for several unidirectional PREs, proving
    adaptive security at a much smaller loss. The loss depends on the graph of users
    whose edges represent the re-encryption keys queried by the adversary. For trees
    and chains the loss is quasi-polynomial in the size and for general graphs it
    is exponential in their depth and indegree (instead of their size as for previous
    reductions). Fortunately, trees and low-depth graphs cover many, if not most,
    interesting applications.\r\n\r\nOur results apply e.g. to the bilinear-map based
    PRE schemes by Ateniese et al. (NDSS’05 and CT-RSA’09), Gentry’s FHE-based scheme
    (STOC’09) and the LWE-based scheme by Chandran et al. (PKC’14)."
alternative_title:
- LNCS
article_processing_charge: No
author:
- first_name: Georg
  full_name: Fuchsbauer, Georg
  id: 46B4C3EE-F248-11E8-B48F-1D18A9856A87
  last_name: Fuchsbauer
- first_name: Chethan
  full_name: Kamath Hosdurg, Chethan
  id: 4BD3F30E-F248-11E8-B48F-1D18A9856A87
  last_name: Kamath Hosdurg
- first_name: Karen
  full_name: Klein, Karen
  id: 3E83A2F8-F248-11E8-B48F-1D18A9856A87
  last_name: Klein
- first_name: Krzysztof Z
  full_name: Pietrzak, Krzysztof Z
  id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
  last_name: Pietrzak
  orcid: 0000-0002-9139-1654
citation:
  ama: 'Fuchsbauer G, Kamath Hosdurg C, Klein K, Pietrzak KZ. Adaptively secure proxy
    re-encryption. In: Vol 11443. Springer Nature; 2019:317-346. doi:<a href="https://doi.org/10.1007/978-3-030-17259-6_11">10.1007/978-3-030-17259-6_11</a>'
  apa: 'Fuchsbauer, G., Kamath Hosdurg, C., Klein, K., &#38; Pietrzak, K. Z. (2019).
    Adaptively secure proxy re-encryption (Vol. 11443, pp. 317–346). Presented at
    the PKC: Public-Key Cryptograhy, Beijing, China: Springer Nature. <a href="https://doi.org/10.1007/978-3-030-17259-6_11">https://doi.org/10.1007/978-3-030-17259-6_11</a>'
  chicago: Fuchsbauer, Georg, Chethan Kamath Hosdurg, Karen Klein, and Krzysztof Z
    Pietrzak. “Adaptively Secure Proxy Re-Encryption,” 11443:317–46. Springer Nature,
    2019. <a href="https://doi.org/10.1007/978-3-030-17259-6_11">https://doi.org/10.1007/978-3-030-17259-6_11</a>.
  ieee: 'G. Fuchsbauer, C. Kamath Hosdurg, K. Klein, and K. Z. Pietrzak, “Adaptively
    secure proxy re-encryption,” presented at the PKC: Public-Key Cryptograhy, Beijing,
    China, 2019, vol. 11443, pp. 317–346.'
  ista: 'Fuchsbauer G, Kamath Hosdurg C, Klein K, Pietrzak KZ. 2019. Adaptively secure
    proxy re-encryption. PKC: Public-Key Cryptograhy, LNCS, vol. 11443, 317–346.'
  mla: Fuchsbauer, Georg, et al. <i>Adaptively Secure Proxy Re-Encryption</i>. Vol.
    11443, Springer Nature, 2019, pp. 317–46, doi:<a href="https://doi.org/10.1007/978-3-030-17259-6_11">10.1007/978-3-030-17259-6_11</a>.
  short: G. Fuchsbauer, C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, in:, Springer
    Nature, 2019, pp. 317–346.
conference:
  end_date: 2019-04-17
  location: Beijing, China
  name: 'PKC: Public-Key Cryptograhy'
  start_date: 2019-04-14
date_created: 2019-05-13T08:13:46Z
date_published: 2019-04-06T00:00:00Z
date_updated: 2023-09-08T11:33:20Z
day: '06'
department:
- _id: KrPi
doi: 10.1007/978-3-030-17259-6_11
ec_funded: 1
intvolume: '     11443'
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://eprint.iacr.org/2018/426
month: '04'
oa: 1
oa_version: Preprint
page: 317-346
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
  call_identifier: H2020
  grant_number: '682815'
  name: Teaching Old Crypto New Tricks
publication_identifier:
  eissn:
  - '16113349'
  isbn:
  - '9783030172589'
  issn:
  - '03029743'
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
  record:
  - id: '10035'
    relation: dissertation_contains
    status: public
scopus_import: '1'
status: public
title: Adaptively secure proxy re-encryption
type: conference
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
volume: 11443
year: '2019'
...