---
_id: '11476'
abstract:
- lang: eng
text: "Messaging platforms like Signal are widely deployed and provide strong security
in an asynchronous setting. It is a challenging problem to construct a protocol
with similar security guarantees that can efficiently scale to large groups. A
major bottleneck are the frequent key rotations users need to perform to achieve
post compromise forward security.\r\n\r\nIn current proposals – most notably in
TreeKEM (which is part of the IETF’s Messaging Layer Security (MLS) protocol draft)
– for users in a group of size n to rotate their keys, they must each craft a
message of size log(n) to be broadcast to the group using an (untrusted) delivery
server.\r\n\r\nIn larger groups, having users sequentially rotate their keys requires
too much bandwidth (or takes too long), so variants allowing any T≤n users to
simultaneously rotate their keys in just 2 communication rounds have been suggested
(e.g. “Propose and Commit” by MLS). Unfortunately, 2-round concurrent updates
are either damaging or expensive (or both); i.e. they either result in future
operations being more costly (e.g. via “blanking” or “tainting”) or are costly
themselves requiring Ω(T) communication for each user [Bienstock et al., TCC’20].\r\n\r\nIn
this paper we propose CoCoA; a new scheme that allows for T concurrent updates
that are neither damaging nor costly. That is, they add no cost to future operations
yet they only require Ω(log2(n)) communication per user. To circumvent the [Bienstock
et al.] lower bound, CoCoA increases the number of rounds needed to complete all
updates from 2 up to (at most) log(n); though typically fewer rounds are needed.\r\n\r\nThe
key insight of our protocol is the following: in the (non-concurrent version of)
TreeKEM, a delivery server which gets T concurrent update requests will approve
one and reject the remaining T−1. In contrast, our server attempts to apply all
of them. If more than one user requests to rotate the same key during a round,
the server arbitrarily picks a winner. Surprisingly, we prove that regardless
of how the server chooses the winners, all previously compromised users will recover
after at most log(n) such update rounds.\r\n\r\nTo keep the communication complexity
low, CoCoA is a server-aided CGKA. That is, the delivery server no longer blindly
forwards packets, but instead actively computes individualized packets tailored
to each user. As the server is untrusted, this change requires us to develop new
mechanisms ensuring robustness of the protocol."
acknowledgement: We thank Marta Mularczyk and Yiannis Tselekounis for their very helpful
feedback on an earlier draft of this paper.
alternative_title:
- LNCS
article_processing_charge: No
author:
- first_name: Joël
full_name: Alwen, Joël
last_name: Alwen
- first_name: Benedikt
full_name: Auerbach, Benedikt
id: D33D2B18-E445-11E9-ABB7-15F4E5697425
last_name: Auerbach
orcid: 0000-0002-7553-6606
- first_name: Miguel
full_name: Cueto Noval, Miguel
id: ffc563a3-f6e0-11ea-865d-e3cce03d17cc
last_name: Cueto Noval
- first_name: Karen
full_name: Klein, Karen
id: 3E83A2F8-F248-11E8-B48F-1D18A9856A87
last_name: Klein
- first_name: Guillermo
full_name: Pascual Perez, Guillermo
id: 2D7ABD02-F248-11E8-B48F-1D18A9856A87
last_name: Pascual Perez
- first_name: Krzysztof Z
full_name: Pietrzak, Krzysztof Z
id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
last_name: Pietrzak
orcid: 0000-0002-9139-1654
- first_name: Michael
full_name: Walter, Michael
last_name: Walter
citation:
ama: 'Alwen J, Auerbach B, Cueto Noval M, et al. CoCoA: Concurrent continuous group
key agreement. In: Advances in Cryptology – EUROCRYPT 2022. Vol 13276.
Cham: Springer Nature; 2022:815–844. doi:10.1007/978-3-031-07085-3_28'
apa: 'Alwen, J., Auerbach, B., Cueto Noval, M., Klein, K., Pascual Perez, G., Pietrzak,
K. Z., & Walter, M. (2022). CoCoA: Concurrent continuous group key agreement.
In Advances in Cryptology – EUROCRYPT 2022 (Vol. 13276, pp. 815–844). Cham:
Springer Nature. https://doi.org/10.1007/978-3-031-07085-3_28'
chicago: 'Alwen, Joël, Benedikt Auerbach, Miguel Cueto Noval, Karen Klein, Guillermo
Pascual Perez, Krzysztof Z Pietrzak, and Michael Walter. “CoCoA: Concurrent Continuous
Group Key Agreement.” In Advances in Cryptology – EUROCRYPT 2022, 13276:815–844.
Cham: Springer Nature, 2022. https://doi.org/10.1007/978-3-031-07085-3_28.'
ieee: 'J. Alwen et al., “CoCoA: Concurrent continuous group key agreement,”
in Advances in Cryptology – EUROCRYPT 2022, Trondheim, Norway, 2022, vol.
13276, pp. 815–844.'
ista: 'Alwen J, Auerbach B, Cueto Noval M, Klein K, Pascual Perez G, Pietrzak KZ,
Walter M. 2022. CoCoA: Concurrent continuous group key agreement. Advances in
Cryptology – EUROCRYPT 2022. EUROCRYPT: Annual International Conference on the
Theory and Applications of Cryptology and Information Security, LNCS, vol. 13276,
815–844.'
mla: 'Alwen, Joël, et al. “CoCoA: Concurrent Continuous Group Key Agreement.” Advances
in Cryptology – EUROCRYPT 2022, vol. 13276, Springer Nature, 2022, pp. 815–844,
doi:10.1007/978-3-031-07085-3_28.'
short: J. Alwen, B. Auerbach, M. Cueto Noval, K. Klein, G. Pascual Perez, K.Z. Pietrzak,
M. Walter, in:, Advances in Cryptology – EUROCRYPT 2022, Springer Nature, Cham,
2022, pp. 815–844.
conference:
end_date: 2022-06-03
location: Trondheim, Norway
name: 'EUROCRYPT: Annual International Conference on the Theory and Applications
of Cryptology and Information Security'
start_date: 2022-05-30
date_created: 2022-06-30T16:48:00Z
date_published: 2022-05-25T00:00:00Z
date_updated: 2023-08-03T07:25:02Z
day: '25'
department:
- _id: GradSch
- _id: KrPi
doi: 10.1007/978-3-031-07085-3_28
ec_funded: 1
external_id:
isi:
- '000832305300028'
intvolume: ' 13276'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2022/251
month: '05'
oa: 1
oa_version: Preprint
page: 815–844
place: Cham
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
- _id: 2564DBCA-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '665385'
name: International IST Doctoral Program
publication: Advances in Cryptology – EUROCRYPT 2022
publication_identifier:
eisbn:
- '9783031070853'
eissn:
- 1611-3349
isbn:
- '9783031070846'
issn:
- 0302-9743
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'CoCoA: Concurrent continuous group key agreement'
type: conference
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 13276
year: '2022'
...
---
_id: '10035'
abstract:
- lang: eng
text: 'Many security definitions come in two flavors: a stronger “adaptive” flavor,
where the adversary can arbitrarily make various choices during the course of
the attack, and a weaker “selective” flavor where the adversary must commit to
some or all of their choices a-priori. For example, in the context of identity-based
encryption, selective security requires the adversary to decide on the identity
of the attacked party at the very beginning of the game whereas adaptive security
allows the attacker to first see the master public key and some secret keys before
making this choice. Often, it appears to be much easier to achieve selective security
than it is to achieve adaptive security. A series of several recent works shows
how to cleverly achieve adaptive security in several such scenarios including
generalized selective decryption [Pan07][FJP15], constrained PRFs [FKPR14], and
Yao’s garbled circuits [JW16]. Although the above works expressed vague intuition
that they share a common technique, the connection was never made precise. In
this work we present a new framework (published at Crypto ’17 [JKK+17a]) that
connects all of these works and allows us to present them in a unified and simplified
fashion. Having the framework in place, we show how to achieve adaptive security
for proxy re-encryption schemes (published at PKC ’19 [FKKP19]) and provide the
first adaptive security proofs for continuous group key agreement protocols (published
at S&P ’21 [KPW+21]). Questioning optimality of our framework, we then show that
currently used proof techniques cannot lead to significantly better security guarantees
for "graph-building" games (published at TCC ’21 [KKPW21a]). These games cover
generalized selective decryption, as well as the security of prominent constructions
for constrained PRFs, continuous group key agreement, and proxy re-encryption.
Finally, we revisit the adaptive security of Yao’s garbled circuits and extend
the analysis of Jafargholi and Wichs in two directions: While they prove adaptive
security only for a modified construction with increased online complexity, we
provide the first positive results for the original construction by Yao (published
at TCC ’21 [KKP21a]). On the negative side, we prove that the results of Jafargholi
and Wichs are essentially optimal by showing that no black-box reduction can provide
a significantly better security bound (published at Crypto ’21 [KKPW21c]).'
acknowledgement: "I want to acknowledge the funding by the European Research Council
(ERC) under the European Union’s Horizon 2020 research and innovation programme
(682815 - TOCNeT).\r\n"
alternative_title:
- ISTA Thesis
article_processing_charge: No
author:
- first_name: Karen
full_name: Klein, Karen
id: 3E83A2F8-F248-11E8-B48F-1D18A9856A87
last_name: Klein
citation:
ama: Klein K. On the adaptive security of graph-based games. 2021. doi:10.15479/at:ista:10035
apa: Klein, K. (2021). On the adaptive security of graph-based games. Institute
of Science and Technology Austria. https://doi.org/10.15479/at:ista:10035
chicago: Klein, Karen. “On the Adaptive Security of Graph-Based Games.” Institute
of Science and Technology Austria, 2021. https://doi.org/10.15479/at:ista:10035.
ieee: K. Klein, “On the adaptive security of graph-based games,” Institute of Science
and Technology Austria, 2021.
ista: Klein K. 2021. On the adaptive security of graph-based games. Institute of
Science and Technology Austria.
mla: Klein, Karen. On the Adaptive Security of Graph-Based Games. Institute
of Science and Technology Austria, 2021, doi:10.15479/at:ista:10035.
short: K. Klein, On the Adaptive Security of Graph-Based Games, Institute of Science
and Technology Austria, 2021.
date_created: 2021-09-23T07:31:44Z
date_published: 2021-09-23T00:00:00Z
date_updated: 2023-10-17T09:24:07Z
day: '23'
ddc:
- '519'
degree_awarded: PhD
department:
- _id: GradSch
- _id: KrPi
doi: 10.15479/at:ista:10035
ec_funded: 1
file:
- access_level: open_access
checksum: 73a44345c683e81f3e765efbf86fdcc5
content_type: application/pdf
creator: cchlebak
date_created: 2021-10-04T12:22:33Z
date_updated: 2021-10-04T12:22:33Z
file_id: '10082'
file_name: thesis_pdfa.pdf
file_size: 2104726
relation: main_file
success: 1
- access_level: closed
checksum: 7b80df30a0e686c3ef6a56d4e1c59e29
content_type: application/x-zip-compressed
creator: cchlebak
date_created: 2021-10-05T07:04:37Z
date_updated: 2022-03-10T12:15:18Z
file_id: '10085'
file_name: thesis_final (1).zip
file_size: 9538359
relation: source_file
file_date_updated: 2022-03-10T12:15:18Z
has_accepted_license: '1'
language:
- iso: eng
month: '09'
oa: 1
oa_version: Published Version
page: '276'
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication_identifier:
issn:
- 2663-337X
publication_status: published
publisher: Institute of Science and Technology Austria
related_material:
record:
- id: '10044'
relation: part_of_dissertation
status: public
- id: '10049'
relation: part_of_dissertation
status: public
- id: '637'
relation: part_of_dissertation
status: public
- id: '10041'
relation: part_of_dissertation
status: public
- id: '6430'
relation: part_of_dissertation
status: public
- id: '10048'
relation: part_of_dissertation
status: public
status: public
supervisor:
- first_name: Krzysztof Z
full_name: Pietrzak, Krzysztof Z
id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
last_name: Pietrzak
orcid: 0000-0002-9139-1654
title: On the adaptive security of graph-based games
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: dissertation
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
year: '2021'
...
---
_id: '10041'
abstract:
- lang: eng
text: Yao’s garbling scheme is one of the most fundamental cryptographic constructions.
Lindell and Pinkas (Journal of Cryptograhy 2009) gave a formal proof of security
in the selective setting where the adversary chooses the challenge inputs before
seeing the garbled circuit assuming secure symmetric-key encryption (and hence
one-way functions). This was followed by results, both positive and negative,
concerning its security in the, stronger, adaptive setting. Applebaum et al. (Crypto
2013) showed that it cannot satisfy adaptive security as is, due to a simple incompressibility
argument. Jafargholi and Wichs (TCC 2017) considered a natural adaptation of Yao’s
scheme (where the output mapping is sent in the online phase, together with the
garbled input) that circumvents this negative result, and proved that it is adaptively
secure, at least for shallow circuits. In particular, they showed that for the
class of circuits of depth δ , the loss in security is at most exponential in δ
. The above results all concern the simulation-based notion of security. In this
work, we show that the upper bound of Jafargholi and Wichs is basically optimal
in a strong sense. As our main result, we show that there exists a family of Boolean
circuits, one for each depth δ∈N , such that any black-box reduction proving
the adaptive indistinguishability of the natural adaptation of Yao’s scheme from
any symmetric-key encryption has to lose a factor that is exponential in δ√
. Since indistinguishability is a weaker notion than simulation, our bound also
applies to adaptive simulation. To establish our results, we build on the recent
approach of Kamath et al. (Eprint 2021), which uses pebbling lower bounds in conjunction
with oracle separations to prove fine-grained lower bounds on loss in cryptographic
security.
acknowledgement: We would like to thank the anonymous reviewers of Crypto’21 whose
detailed comments helped us considerably improve the presentation of the paper.
alternative_title:
- LCNS
article_processing_charge: No
author:
- 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
- first_name: Daniel
full_name: Wichs, Daniel
last_name: Wichs
citation:
ama: 'Kamath Hosdurg C, Klein K, Pietrzak KZ, Wichs D. Limits on the Adaptive Security
of Yao’s Garbling. In: 41st Annual International Cryptology Conference, Part
II . Vol 12826. Cham: Springer Nature; 2021:486-515. doi:10.1007/978-3-030-84245-1_17'
apa: 'Kamath Hosdurg, C., Klein, K., Pietrzak, K. Z., & Wichs, D. (2021). Limits
on the Adaptive Security of Yao’s Garbling. In 41st Annual International Cryptology
Conference, Part II (Vol. 12826, pp. 486–515). Cham: Springer Nature. https://doi.org/10.1007/978-3-030-84245-1_17'
chicago: 'Kamath Hosdurg, Chethan, Karen Klein, Krzysztof Z Pietrzak, and Daniel
Wichs. “Limits on the Adaptive Security of Yao’s Garbling.” In 41st Annual
International Cryptology Conference, Part II , 12826:486–515. Cham: Springer
Nature, 2021. https://doi.org/10.1007/978-3-030-84245-1_17.'
ieee: C. Kamath Hosdurg, K. Klein, K. Z. Pietrzak, and D. Wichs, “Limits on the
Adaptive Security of Yao’s Garbling,” in 41st Annual International Cryptology
Conference, Part II , Virtual, 2021, vol. 12826, pp. 486–515.
ista: 'Kamath Hosdurg C, Klein K, Pietrzak KZ, Wichs D. 2021. Limits on the Adaptive
Security of Yao’s Garbling. 41st Annual International Cryptology Conference, Part
II . CRYPTO: Annual International Cryptology Conference, LCNS, vol. 12826, 486–515.'
mla: Kamath Hosdurg, Chethan, et al. “Limits on the Adaptive Security of Yao’s Garbling.”
41st Annual International Cryptology Conference, Part II , vol. 12826,
Springer Nature, 2021, pp. 486–515, doi:10.1007/978-3-030-84245-1_17.
short: C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, D. Wichs, in:, 41st Annual International
Cryptology Conference, Part II , Springer Nature, Cham, 2021, pp. 486–515.
conference:
end_date: 2021-08-20
location: Virtual
name: 'CRYPTO: Annual International Cryptology Conference'
start_date: 2021-08-16
date_created: 2021-09-23T14:06:15Z
date_published: 2021-08-11T00:00:00Z
date_updated: 2023-09-07T13:32:11Z
day: '11'
department:
- _id: KrPi
doi: 10.1007/978-3-030-84245-1_17
ec_funded: 1
intvolume: ' 12826'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2021/945
month: '08'
oa: 1
oa_version: Preprint
page: 486-515
place: Cham
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: '41st Annual International Cryptology Conference, Part II '
publication_identifier:
eisbn:
- 978-3-030-84245-1
eissn:
- 1611-3349
isbn:
- 978-3-030-84244-4
issn:
- 0302-9743
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
record:
- id: '10035'
relation: dissertation_contains
status: public
status: public
title: Limits on the Adaptive Security of Yao’s Garbling
type: conference
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
volume: 12826
year: '2021'
...
---
_id: '10044'
abstract:
- lang: eng
text: We show that Yao’s garbling scheme is adaptively indistinguishable for the
class of Boolean circuits of size S and treewidth w with only a S^O(w) loss in
security. For instance, circuits with constant treewidth are as a result adaptively
indistinguishable with only a polynomial loss. This (partially) complements a
negative result of Applebaum et al. (Crypto 2013), which showed (assuming one-way
functions) that Yao’s garbling scheme cannot be adaptively simulatable. As main
technical contributions, we introduce a new pebble game that abstracts out our
security reduction and then present a pebbling strategy for this game where the
number of pebbles used is roughly O(d w log(S)), d being the fan-out of the circuit.
The design of the strategy relies on separators, a graph-theoretic notion with
connections to circuit complexity.
acknowledgement: 'We would like to thank Daniel Wichs for helpful discussions on the
landscape of adaptive security of Yao’s garbling. '
article_number: 2021/926
article_processing_charge: No
author:
- 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: 'Kamath Hosdurg C, Klein K, Pietrzak KZ. On treewidth, separators and Yao’s
garbling. In: 19th Theory of Cryptography Conference 2021. International
Association for Cryptologic Research; 2021.'
apa: 'Kamath Hosdurg, C., Klein, K., & Pietrzak, K. Z. (2021). On treewidth,
separators and Yao’s garbling. In 19th Theory of Cryptography Conference 2021.
Raleigh, NC, United States: International Association for Cryptologic Research.'
chicago: Kamath Hosdurg, Chethan, Karen Klein, and Krzysztof Z Pietrzak. “On Treewidth,
Separators and Yao’s Garbling.” In 19th Theory of Cryptography Conference 2021.
International Association for Cryptologic Research, 2021.
ieee: C. Kamath Hosdurg, K. Klein, and K. Z. Pietrzak, “On treewidth, separators
and Yao’s garbling,” in 19th Theory of Cryptography Conference 2021, Raleigh,
NC, United States, 2021.
ista: 'Kamath Hosdurg C, Klein K, Pietrzak KZ. 2021. On treewidth, separators and
Yao’s garbling. 19th Theory of Cryptography Conference 2021. TCC: Theory of Cryptography
Conference, 2021/926.'
mla: Kamath Hosdurg, Chethan, et al. “On Treewidth, Separators and Yao’s Garbling.”
19th Theory of Cryptography Conference 2021, 2021/926, International Association
for Cryptologic Research, 2021.
short: C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, in:, 19th Theory of Cryptography
Conference 2021, International Association for Cryptologic Research, 2021.
conference:
end_date: 2021-11-11
location: Raleigh, NC, United States
name: 'TCC: Theory of Cryptography Conference'
start_date: 2021-11-08
date_created: 2021-09-24T12:01:34Z
date_published: 2021-07-08T00:00:00Z
date_updated: 2023-09-07T13:32:11Z
day: '08'
department:
- _id: KrPi
ec_funded: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2021/926
month: '07'
oa: 1
oa_version: Preprint
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: 19th Theory of Cryptography Conference 2021
publication_status: published
publisher: International Association for Cryptologic Research
quality_controlled: '1'
related_material:
record:
- id: '10409'
relation: later_version
status: public
- id: '10035'
relation: dissertation_contains
status: public
status: public
title: On treewidth, separators and Yao's garbling
type: conference
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
year: '2021'
...
---
_id: '10048'
abstract:
- lang: eng
text: "The security of cryptographic primitives and protocols against adversaries
that are allowed to make adaptive choices (e.g., which parties to corrupt or which
queries to make) is notoriously difficult to establish. A broad theoretical\r\nframework
was introduced by Jafargholi et al. [Crypto’17] for this purpose. In this paper
we initiate the study of lower bounds on loss in adaptive security for certain
cryptographic protocols considered in the framework. We prove lower\r\nbounds
that almost match the upper bounds (proven using the framework) for proxy re-encryption,
prefix-constrained PRFs and generalized selective decryption, a security game
that captures the security of certain group messaging and\r\nbroadcast encryption
schemes. Those primitives have in common that their security game involves an
underlying graph that can be adaptively built by the adversary. Some of our lower
bounds only apply to a restricted class of black-box reductions which we term
“oblivious” (the existing upper bounds are of this restricted type), some apply
to the broader but still restricted class of non-rewinding reductions, while our
lower bound for proxy re-encryption applies to all black-box reductions. The fact
that some of our lower bounds seem to crucially rely on obliviousness or at least
a non-rewinding reduction hints to the exciting possibility that the existing
upper bounds can be improved by using more sophisticated reductions. Our main
conceptual contribution is a two-player multi-stage game called the Builder-Pebbler
Game. We can translate bounds on the winning probabilities for various instantiations
of this game into cryptographic lower bounds for the above-mentioned primitives
using oracle separation techniques.\r\n"
article_processing_charge: No
author:
- 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
- first_name: Michael
full_name: Walter, Michael
id: 488F98B0-F248-11E8-B48F-1D18A9856A87
last_name: Walter
orcid: 0000-0003-3186-2482
citation:
ama: 'Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. The cost of adaptivity in
security games on graphs. In: 19th Theory of Cryptography Conference 2021.
International Association for Cryptologic Research; 2021.'
apa: 'Kamath Hosdurg, C., Klein, K., Pietrzak, K. Z., & Walter, M. (2021). The
cost of adaptivity in security games on graphs. In 19th Theory of Cryptography
Conference 2021. Raleigh, NC, United States: International Association for
Cryptologic Research.'
chicago: Kamath Hosdurg, Chethan, Karen Klein, Krzysztof Z Pietrzak, and Michael
Walter. “The Cost of Adaptivity in Security Games on Graphs.” In 19th Theory
of Cryptography Conference 2021. International Association for Cryptologic
Research, 2021.
ieee: C. Kamath Hosdurg, K. Klein, K. Z. Pietrzak, and M. Walter, “The cost of adaptivity
in security games on graphs,” in 19th Theory of Cryptography Conference 2021,
Raleigh, NC, United States, 2021.
ista: 'Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. 2021. The cost of adaptivity
in security games on graphs. 19th Theory of Cryptography Conference 2021. TCC:
Theory of Cryptography Conference.'
mla: Kamath Hosdurg, Chethan, et al. “The Cost of Adaptivity in Security Games on
Graphs.” 19th Theory of Cryptography Conference 2021, International Association
for Cryptologic Research, 2021.
short: C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, M. Walter, in:, 19th Theory of
Cryptography Conference 2021, International Association for Cryptologic Research,
2021.
conference:
end_date: 2021-11-11
location: Raleigh, NC, United States
name: 'TCC: Theory of Cryptography Conference'
start_date: 2021-11-08
date_created: 2021-09-27T12:52:05Z
date_published: 2021-07-08T00:00:00Z
date_updated: 2023-10-17T09:24:08Z
day: '08'
department:
- _id: KrPi
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://ia.cr/2021/059
month: '07'
oa: 1
oa_version: Preprint
publication: 19th Theory of Cryptography Conference 2021
publication_status: published
publisher: International Association for Cryptologic Research
quality_controlled: '1'
related_material:
record:
- id: '10410'
relation: later_version
status: public
- id: '10035'
relation: dissertation_contains
status: public
status: public
title: The cost of adaptivity in security games on graphs
type: conference
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
year: '2021'
...
---
_id: '10049'
abstract:
- lang: eng
text: While messaging systems with strong security guarantees are widely used in
practice, designing a protocol that scales efficiently to large groups and enjoys
similar security guarantees remains largely open. The two existing proposals to
date are ART (Cohn-Gordon et al., CCS18) and TreeKEM (IETF, The Messaging Layer
Security Protocol, draft). TreeKEM is the currently considered candidate by the
IETF MLS working group, but dynamic group operations (i.e. adding and removing
users) can cause efficiency issues. In this paper we formalize and analyze a variant
of TreeKEM which we term Tainted TreeKEM (TTKEM for short). The basic idea underlying
TTKEM was suggested by Millican (MLS mailing list, February 2018). This version
is more efficient than TreeKEM for some natural distributions of group operations,
we quantify this through simulations.Our second contribution is two security proofs
for TTKEM which establish post compromise and forward secrecy even against adaptive
attackers. The security loss (to the underlying PKE) in the Random Oracle Model
is a polynomial factor, and a quasipolynomial one in the Standard Model. Our proofs
can be adapted to TreeKEM as well. Before our work no security proof for any TreeKEM-like
protocol establishing tight security against an adversary who can adaptively choose
the sequence of operations was known. We also are the first to prove (or even
formalize) active security where the server can arbitrarily deviate from the protocol
specification. Proving fully active security – where also the users can arbitrarily
deviate – remains open.
acknowledgement: The first three authors contributed equally to this work. Funded
by the European Research Council (ERC) under the European Union’s Horizon2020 research
and innovation programme (682815-TOCNeT). Funded by the European Union’s Horizon
2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement
No.665385.
article_processing_charge: No
author:
- first_name: Karen
full_name: Klein, Karen
id: 3E83A2F8-F248-11E8-B48F-1D18A9856A87
last_name: Klein
- first_name: Guillermo
full_name: Pascual Perez, Guillermo
id: 2D7ABD02-F248-11E8-B48F-1D18A9856A87
last_name: Pascual Perez
orcid: 0000-0001-8630-415X
- first_name: Michael
full_name: Walter, Michael
id: 488F98B0-F248-11E8-B48F-1D18A9856A87
last_name: Walter
orcid: 0000-0003-3186-2482
- first_name: Chethan
full_name: Kamath Hosdurg, Chethan
id: 4BD3F30E-F248-11E8-B48F-1D18A9856A87
last_name: Kamath Hosdurg
- first_name: Margarita
full_name: Capretto, Margarita
last_name: Capretto
- first_name: Miguel
full_name: Cueto Noval, Miguel
id: ffc563a3-f6e0-11ea-865d-e3cce03d17cc
last_name: Cueto Noval
- first_name: Ilia
full_name: Markov, Ilia
id: D0CF4148-C985-11E9-8066-0BDEE5697425
last_name: Markov
- first_name: Michelle X
full_name: Yeo, Michelle X
id: 2D82B818-F248-11E8-B48F-1D18A9856A87
last_name: Yeo
- first_name: Joel F
full_name: Alwen, Joel F
id: 2A8DFA8C-F248-11E8-B48F-1D18A9856A87
last_name: Alwen
- 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: 'Klein K, Pascual Perez G, Walter M, et al. Keep the dirt: tainted TreeKEM,
adaptively and actively secure continuous group key agreement. In: 2021 IEEE
Symposium on Security and Privacy . IEEE; 2021:268-284. doi:10.1109/sp40001.2021.00035'
apa: 'Klein, K., Pascual Perez, G., Walter, M., Kamath Hosdurg, C., Capretto, M.,
Cueto Noval, M., … Pietrzak, K. Z. (2021). Keep the dirt: tainted TreeKEM, adaptively
and actively secure continuous group key agreement. In 2021 IEEE Symposium
on Security and Privacy (pp. 268–284). San Francisco, CA, United States:
IEEE. https://doi.org/10.1109/sp40001.2021.00035'
chicago: 'Klein, Karen, Guillermo Pascual Perez, Michael Walter, Chethan Kamath
Hosdurg, Margarita Capretto, Miguel Cueto Noval, Ilia Markov, Michelle X Yeo,
Joel F Alwen, and Krzysztof Z Pietrzak. “Keep the Dirt: Tainted TreeKEM, Adaptively
and Actively Secure Continuous Group Key Agreement.” In 2021 IEEE Symposium
on Security and Privacy , 268–84. IEEE, 2021. https://doi.org/10.1109/sp40001.2021.00035.'
ieee: 'K. Klein et al., “Keep the dirt: tainted TreeKEM, adaptively and actively
secure continuous group key agreement,” in 2021 IEEE Symposium on Security
and Privacy , San Francisco, CA, United States, 2021, pp. 268–284.'
ista: 'Klein K, Pascual Perez G, Walter M, Kamath Hosdurg C, Capretto M, Cueto Noval
M, Markov I, Yeo MX, Alwen JF, Pietrzak KZ. 2021. Keep the dirt: tainted TreeKEM,
adaptively and actively secure continuous group key agreement. 2021 IEEE Symposium
on Security and Privacy . SP: Symposium on Security and Privacy, 268–284.'
mla: 'Klein, Karen, et al. “Keep the Dirt: Tainted TreeKEM, Adaptively and Actively
Secure Continuous Group Key Agreement.” 2021 IEEE Symposium on Security and
Privacy , IEEE, 2021, pp. 268–84, doi:10.1109/sp40001.2021.00035.'
short: K. Klein, G. Pascual Perez, M. Walter, C. Kamath Hosdurg, M. Capretto, M.
Cueto Noval, I. Markov, M.X. Yeo, J.F. Alwen, K.Z. Pietrzak, in:, 2021 IEEE Symposium
on Security and Privacy , IEEE, 2021, pp. 268–284.
conference:
end_date: 2021-05-27
location: San Francisco, CA, United States
name: 'SP: Symposium on Security and Privacy'
start_date: 2021-05-24
date_created: 2021-09-27T13:46:27Z
date_published: 2021-08-26T00:00:00Z
date_updated: 2023-09-07T13:32:11Z
day: '26'
department:
- _id: KrPi
- _id: DaAl
doi: 10.1109/sp40001.2021.00035
ec_funded: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2019/1489
month: '08'
oa: 1
oa_version: Preprint
page: 268-284
project:
- _id: 2564DBCA-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '665385'
name: International IST Doctoral Program
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: '2021 IEEE Symposium on Security and Privacy '
publication_status: published
publisher: IEEE
quality_controlled: '1'
related_material:
record:
- id: '10035'
relation: dissertation_contains
status: public
status: public
title: 'Keep the dirt: tainted TreeKEM, adaptively and actively secure continuous
group key agreement'
type: conference
user_id: 8b945eb4-e2f2-11eb-945a-df72226e66a9
year: '2021'
...
---
_id: '10408'
abstract:
- lang: eng
text: 'Key trees are often the best solution in terms of transmission cost and storage
requirements for managing keys in a setting where a group needs to share a secret
key, while being able to efficiently rotate the key material of users (in order
to recover from a potential compromise, or to add or remove users). Applications
include multicast encryption protocols like LKH (Logical Key Hierarchies) or group
messaging like the current IETF proposal TreeKEM. A key tree is a (typically balanced)
binary tree, where each node is identified with a key: leaf nodes hold users’
secret keys while the root is the shared group key. For a group of size N, each
user just holds log(N) keys (the keys on the path from its leaf to the root)
and its entire key material can be rotated by broadcasting 2log(N) ciphertexts
(encrypting each fresh key on the path under the keys of its parents). In this
work we consider the natural setting where we have many groups with partially
overlapping sets of users, and ask if we can find solutions where the cost of
rotating a key is better than in the trivial one where we have a separate key
tree for each group. We show that in an asymptotic setting (where the number m
of groups is fixed while the number N of users grows) there exist more general
key graphs whose cost converges to the cost of a single group, thus saving a factor
linear in the number of groups over the trivial solution. As our asymptotic “solution”
converges very slowly and performs poorly on concrete examples, we propose an
algorithm that uses a natural heuristic to compute a key graph for any given group
structure. Our algorithm combines two greedy algorithms, and is thus very efficient:
it first converts the group structure into a “lattice graph”, which is then turned
into a key graph by repeatedly applying the algorithm for constructing a Huffman
code. To better understand how far our proposal is from an optimal solution, we
prove lower bounds on the update cost of continuous group-key agreement and multicast
encryption in a symbolic model admitting (asymmetric) encryption, pseudorandom
generators, and secret sharing as building blocks.'
acknowledgement: B. Auerbach, M.A. Baig and K. Pietrzak—received funding from the
European Research Council (ERC) under the European Union’s Horizon 2020 research
and innovation programme (682815 - TOCNeT); Karen Klein was supported in part by
ERC CoG grant 724307 and conducted part of this work at IST Austria, funded by the
ERC under the European Union’s Horizon 2020 research and innovation programme (682815
- TOCNeT); Guillermo Pascual-Perez was funded by the European Union’s Horizon 2020
research and innovation programme under the Marie Skłodowska-Curie Grant Agreement
No. 665385; Michael Walter conducted part of this work at IST Austria, funded by
the ERC under the European Union’s Horizon 2020 research and innovation programme
(682815 - TOCNeT).
alternative_title:
- LNCS
article_processing_charge: No
author:
- first_name: Joel F
full_name: Alwen, Joel F
id: 2A8DFA8C-F248-11E8-B48F-1D18A9856A87
last_name: Alwen
- first_name: Benedikt
full_name: Auerbach, Benedikt
id: D33D2B18-E445-11E9-ABB7-15F4E5697425
last_name: Auerbach
orcid: 0000-0002-7553-6606
- first_name: Mirza Ahad
full_name: Baig, Mirza Ahad
id: 3EDE6DE4-AA5A-11E9-986D-341CE6697425
last_name: Baig
- first_name: Miguel
full_name: Cueto Noval, Miguel
id: ffc563a3-f6e0-11ea-865d-e3cce03d17cc
last_name: Cueto Noval
- first_name: Karen
full_name: Klein, Karen
id: 3E83A2F8-F248-11E8-B48F-1D18A9856A87
last_name: Klein
- first_name: Guillermo
full_name: Pascual Perez, Guillermo
id: 2D7ABD02-F248-11E8-B48F-1D18A9856A87
last_name: Pascual Perez
orcid: 0000-0001-8630-415X
- first_name: Krzysztof Z
full_name: Pietrzak, Krzysztof Z
id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
last_name: Pietrzak
orcid: 0000-0002-9139-1654
- first_name: Michael
full_name: Walter, Michael
id: 488F98B0-F248-11E8-B48F-1D18A9856A87
last_name: Walter
orcid: 0000-0003-3186-2482
citation:
ama: 'Alwen JF, Auerbach B, Baig MA, et al. Grafting key trees: Efficient key management
for overlapping groups. In: 19th International Conference. Vol 13044. Springer
Nature; 2021:222-253. doi:10.1007/978-3-030-90456-2_8'
apa: 'Alwen, J. F., Auerbach, B., Baig, M. A., Cueto Noval, M., Klein, K., Pascual
Perez, G., … Walter, M. (2021). Grafting key trees: Efficient key management for
overlapping groups. In 19th International Conference (Vol. 13044, pp. 222–253).
Raleigh, NC, United States: Springer Nature. https://doi.org/10.1007/978-3-030-90456-2_8'
chicago: 'Alwen, Joel F, Benedikt Auerbach, Mirza Ahad Baig, Miguel Cueto Noval,
Karen Klein, Guillermo Pascual Perez, Krzysztof Z Pietrzak, and Michael Walter.
“Grafting Key Trees: Efficient Key Management for Overlapping Groups.” In 19th
International Conference, 13044:222–53. Springer Nature, 2021. https://doi.org/10.1007/978-3-030-90456-2_8.'
ieee: 'J. F. Alwen et al., “Grafting key trees: Efficient key management
for overlapping groups,” in 19th International Conference, Raleigh, NC,
United States, 2021, vol. 13044, pp. 222–253.'
ista: 'Alwen JF, Auerbach B, Baig MA, Cueto Noval M, Klein K, Pascual Perez G, Pietrzak
KZ, Walter M. 2021. Grafting key trees: Efficient key management for overlapping
groups. 19th International Conference. TCC: Theory of Cryptography, LNCS, vol.
13044, 222–253.'
mla: 'Alwen, Joel F., et al. “Grafting Key Trees: Efficient Key Management for Overlapping
Groups.” 19th International Conference, vol. 13044, Springer Nature, 2021,
pp. 222–53, doi:10.1007/978-3-030-90456-2_8.'
short: J.F. Alwen, B. Auerbach, M.A. Baig, M. Cueto Noval, K. Klein, G. Pascual
Perez, K.Z. Pietrzak, M. Walter, in:, 19th International Conference, Springer
Nature, 2021, pp. 222–253.
conference:
end_date: 2021-11-11
location: Raleigh, NC, United States
name: 'TCC: Theory of Cryptography'
start_date: 2021-11-08
date_created: 2021-12-05T23:01:42Z
date_published: 2021-11-04T00:00:00Z
date_updated: 2023-08-14T13:19:39Z
day: '04'
department:
- _id: KrPi
doi: 10.1007/978-3-030-90456-2_8
ec_funded: 1
external_id:
isi:
- '000728363700008'
intvolume: ' 13044'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2021/1158
month: '11'
oa: 1
oa_version: Preprint
page: 222-253
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
- _id: 2564DBCA-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '665385'
name: International IST Doctoral Program
publication: 19th International Conference
publication_identifier:
eisbn:
- 978-3-030-90456-2
eissn:
- 1611-3349
isbn:
- 9-783-0309-0455-5
issn:
- 0302-9743
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
scopus_import: '1'
status: public
title: 'Grafting key trees: Efficient key management for overlapping groups'
type: conference
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 13044
year: '2021'
...
---
_id: '10409'
abstract:
- lang: eng
text: We show that Yao’s garbling scheme is adaptively indistinguishable for the
class of Boolean circuits of size S and treewidth w with only a SO(w) loss
in security. For instance, circuits with constant treewidth are as a result adaptively
indistinguishable with only a polynomial loss. This (partially) complements a
negative result of Applebaum et al. (Crypto 2013), which showed (assuming one-way
functions) that Yao’s garbling scheme cannot be adaptively simulatable. As main
technical contributions, we introduce a new pebble game that abstracts out our
security reduction and then present a pebbling strategy for this game where the
number of pebbles used is roughly O(δwlog(S)) , δ being the fan-out of the
circuit. The design of the strategy relies on separators, a graph-theoretic notion
with connections to circuit complexity. with only a SO(w) loss in security.
For instance, circuits with constant treewidth are as a result adaptively indistinguishable
with only a polynomial loss. This (partially) complements a negative result of
Applebaum et al. (Crypto 2013), which showed (assuming one-way functions) that
Yao’s garbling scheme cannot be adaptively simulatable. As main technical contributions,
we introduce a new pebble game that abstracts out our security reduction and then
present a pebbling strategy for this game where the number of pebbles used is
roughly O(δwlog(S)) , δ being the fan-out of the circuit. The design of the
strategy relies on separators, a graph-theoretic notion with connections to circuit
complexity.
acknowledgement: We are grateful to Daniel Wichs for helpful discussions on the landscape
of adaptive security of Yao’s garbling. We would also like to thank Crypto 2021
and TCC 2021 reviewers for their detailed review and suggestions, which helped improve
presentation considerably.
alternative_title:
- LNCS
article_processing_charge: No
author:
- 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: 'Kamath Hosdurg C, Klein K, Pietrzak KZ. On treewidth, separators and Yao’s
garbling. In: 19th International Conference. Vol 13043. Springer Nature;
2021:486-517. doi:10.1007/978-3-030-90453-1_17'
apa: 'Kamath Hosdurg, C., Klein, K., & Pietrzak, K. Z. (2021). On treewidth,
separators and Yao’s garbling. In 19th International Conference (Vol. 13043,
pp. 486–517). Raleigh, NC, United States: Springer Nature. https://doi.org/10.1007/978-3-030-90453-1_17'
chicago: Kamath Hosdurg, Chethan, Karen Klein, and Krzysztof Z Pietrzak. “On Treewidth,
Separators and Yao’s Garbling.” In 19th International Conference, 13043:486–517.
Springer Nature, 2021. https://doi.org/10.1007/978-3-030-90453-1_17.
ieee: C. Kamath Hosdurg, K. Klein, and K. Z. Pietrzak, “On treewidth, separators
and Yao’s garbling,” in 19th International Conference, Raleigh, NC, United
States, 2021, vol. 13043, pp. 486–517.
ista: 'Kamath Hosdurg C, Klein K, Pietrzak KZ. 2021. On treewidth, separators and
Yao’s garbling. 19th International Conference. TCC: Theory of Cryptography, LNCS,
vol. 13043, 486–517.'
mla: Kamath Hosdurg, Chethan, et al. “On Treewidth, Separators and Yao’s Garbling.”
19th International Conference, vol. 13043, Springer Nature, 2021, pp. 486–517,
doi:10.1007/978-3-030-90453-1_17.
short: C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, in:, 19th International Conference,
Springer Nature, 2021, pp. 486–517.
conference:
end_date: 2021-11-11
location: Raleigh, NC, United States
name: 'TCC: Theory of Cryptography'
start_date: 2021-11-08
date_created: 2021-12-05T23:01:43Z
date_published: 2021-11-04T00:00:00Z
date_updated: 2023-08-17T06:21:38Z
day: '04'
department:
- _id: KrPi
doi: 10.1007/978-3-030-90453-1_17
ec_funded: 1
external_id:
isi:
- '000728364000017'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2021/926
month: '11'
oa: 1
oa_version: Preprint
page: 486-517
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: 19th International Conference
publication_identifier:
eissn:
- 1611-3349
isbn:
- 9-783-0309-0452-4
issn:
- 0302-9743
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
record:
- id: '10044'
relation: earlier_version
status: public
scopus_import: '1'
status: public
title: On treewidth, separators and Yao’s garbling
type: conference
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: '13043 '
year: '2021'
...
---
_id: '10410'
abstract:
- lang: eng
text: The security of cryptographic primitives and protocols against adversaries
that are allowed to make adaptive choices (e.g., which parties to corrupt or which
queries to make) is notoriously difficult to establish. A broad theoretical framework
was introduced by Jafargholi et al. [Crypto’17] for this purpose. In this paper
we initiate the study of lower bounds on loss in adaptive security for certain
cryptographic protocols considered in the framework. We prove lower bounds that
almost match the upper bounds (proven using the framework) for proxy re-encryption,
prefix-constrained PRFs and generalized selective decryption, a security game
that captures the security of certain group messaging and broadcast encryption
schemes. Those primitives have in common that their security game involves an
underlying graph that can be adaptively built by the adversary. Some of our lower
bounds only apply to a restricted class of black-box reductions which we term
“oblivious” (the existing upper bounds are of this restricted type), some apply
to the broader but still restricted class of non-rewinding reductions, while our
lower bound for proxy re-encryption applies to all black-box reductions. The fact
that some of our lower bounds seem to crucially rely on obliviousness or at least
a non-rewinding reduction hints to the exciting possibility that the existing
upper bounds can be improved by using more sophisticated reductions. Our main
conceptual contribution is a two-player multi-stage game called the Builder-Pebbler
Game. We can translate bounds on the winning probabilities for various instantiations
of this game into cryptographic lower bounds for the above-mentioned primitives
using oracle separation techniques.
acknowledgement: C. Kamath—Supported by Azrieli International Postdoctoral Fellowship.
Most of the work was done while the author was at Northeastern University and Charles
University, funded by the IARPA grant IARPA/2019-19-020700009 and project PRIMUS/17/SCI/9,
respectively. K. Klein—Supported in part by ERC CoG grant 724307. Most of the work
was done while the author was at IST Austria funded by the European Research Council
(ERC) under the European Union’s Horizon 2020 research and innovation programme
(682815 - TOCNeT). K. Pietrzak—Funded by the European Research Council (ERC) under
the European Union’s Horizon 2020 research and innovation programme (682815 - TOCNeT).
alternative_title:
- LNCS
article_processing_charge: No
author:
- 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
- first_name: Michael
full_name: Walter, Michael
id: 488F98B0-F248-11E8-B48F-1D18A9856A87
last_name: Walter
orcid: 0000-0003-3186-2482
citation:
ama: 'Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. The cost of adaptivity in
security games on graphs. In: 19th International Conference. Vol 13043.
Springer Nature; 2021:550-581. doi:10.1007/978-3-030-90453-1_19'
apa: 'Kamath Hosdurg, C., Klein, K., Pietrzak, K. Z., & Walter, M. (2021). The
cost of adaptivity in security games on graphs. In 19th International Conference
(Vol. 13043, pp. 550–581). Raleigh, NC, United States: Springer Nature. https://doi.org/10.1007/978-3-030-90453-1_19'
chicago: Kamath Hosdurg, Chethan, Karen Klein, Krzysztof Z Pietrzak, and Michael
Walter. “The Cost of Adaptivity in Security Games on Graphs.” In 19th International
Conference, 13043:550–81. Springer Nature, 2021. https://doi.org/10.1007/978-3-030-90453-1_19.
ieee: C. Kamath Hosdurg, K. Klein, K. Z. Pietrzak, and M. Walter, “The cost of adaptivity
in security games on graphs,” in 19th International Conference, Raleigh,
NC, United States, 2021, vol. 13043, pp. 550–581.
ista: 'Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. 2021. The cost of adaptivity
in security games on graphs. 19th International Conference. TCC: Theory of Cryptography,
LNCS, vol. 13043, 550–581.'
mla: Kamath Hosdurg, Chethan, et al. “The Cost of Adaptivity in Security Games on
Graphs.” 19th International Conference, vol. 13043, Springer Nature, 2021,
pp. 550–81, doi:10.1007/978-3-030-90453-1_19.
short: C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, M. Walter, in:, 19th International
Conference, Springer Nature, 2021, pp. 550–581.
conference:
end_date: 2021-11-11
location: Raleigh, NC, United States
name: 'TCC: Theory of Cryptography'
start_date: 2021-11-08
date_created: 2021-12-05T23:01:43Z
date_published: 2021-11-04T00:00:00Z
date_updated: 2023-10-17T09:24:07Z
day: '04'
department:
- _id: KrPi
doi: 10.1007/978-3-030-90453-1_19
ec_funded: 1
external_id:
isi:
- '000728364000019'
intvolume: ' 13043'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://ia.cr/2021/059
month: '11'
oa: 1
oa_version: Preprint
page: 550-581
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: 19th International Conference
publication_identifier:
eissn:
- 1611-3349
isbn:
- 9-783-0309-0452-4
issn:
- 0302-9743
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
related_material:
record:
- id: '10048'
relation: earlier_version
status: public
scopus_import: '1'
status: public
title: The cost of adaptivity in security games on graphs
type: conference
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 13043
year: '2021'
...
---
_id: '9826'
abstract:
- lang: eng
text: "Automated contract tracing aims at supporting manual contact tracing during
pandemics by alerting users of encounters with infected people. There are currently
many proposals for protocols (like the “decentralized” DP-3T and PACT or the “centralized”
ROBERT and DESIRE) to be run on mobile phones, where the basic idea is to regularly
broadcast (using low energy Bluetooth) some values, and at the same time store
(a function of) incoming messages broadcasted by users in their proximity. In
the existing proposals one can trigger false positives on a massive scale by an
“inverse-Sybil” attack, where a large number of devices (malicious users or hacked
phones) pretend to be the same user, such that later, just a single person needs
to be diagnosed (and allowed to upload) to trigger an alert for all users who
were in proximity to any of this large group of devices.\r\n\r\nWe propose the
first protocols that do not succumb to such attacks assuming the devices involved
in the attack do not constantly communicate, which we observe is a necessary assumption.
The high level idea of the protocols is to derive the values to be broadcasted
by a hash chain, so that two (or more) devices who want to launch an inverse-Sybil
attack will not be able to connect their respective chains and thus only one of
them will be able to upload. Our protocols also achieve security against replay,
belated replay, and one of them even against relay attacks."
acknowledgement: Guillermo Pascual-Perez and Michelle Yeo were funded by the European
Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska–Curie
Grant Agreement No. 665385; the remaining contributors to this project have received
funding from the European Research Council (ERC) under the European Union’s Horizon
2020 research and innovation programme (682815 - TOCNeT).
alternative_title:
- LNCS
article_processing_charge: No
author:
- first_name: Benedikt
full_name: Auerbach, Benedikt
id: D33D2B18-E445-11E9-ABB7-15F4E5697425
last_name: Auerbach
orcid: 0000-0002-7553-6606
- first_name: Suvradip
full_name: Chakraborty, Suvradip
id: B9CD0494-D033-11E9-B219-A439E6697425
last_name: Chakraborty
- first_name: Karen
full_name: Klein, Karen
id: 3E83A2F8-F248-11E8-B48F-1D18A9856A87
last_name: Klein
- first_name: Guillermo
full_name: Pascual Perez, Guillermo
id: 2D7ABD02-F248-11E8-B48F-1D18A9856A87
last_name: Pascual Perez
- first_name: Krzysztof Z
full_name: Pietrzak, Krzysztof Z
id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
last_name: Pietrzak
orcid: 0000-0002-9139-1654
- first_name: Michael
full_name: Walter, Michael
id: 488F98B0-F248-11E8-B48F-1D18A9856A87
last_name: Walter
orcid: 0000-0003-3186-2482
- first_name: Michelle X
full_name: Yeo, Michelle X
id: 2D82B818-F248-11E8-B48F-1D18A9856A87
last_name: Yeo
citation:
ama: 'Auerbach B, Chakraborty S, Klein K, et al. Inverse-Sybil attacks in automated
contact tracing. In: Topics in Cryptology – CT-RSA 2021. Vol 12704. Springer
Nature; 2021:399-421. doi:10.1007/978-3-030-75539-3_17'
apa: 'Auerbach, B., Chakraborty, S., Klein, K., Pascual Perez, G., Pietrzak, K.
Z., Walter, M., & Yeo, M. X. (2021). Inverse-Sybil attacks in automated contact
tracing. In Topics in Cryptology – CT-RSA 2021 (Vol. 12704, pp. 399–421).
Virtual Event: Springer Nature. https://doi.org/10.1007/978-3-030-75539-3_17'
chicago: Auerbach, Benedikt, Suvradip Chakraborty, Karen Klein, Guillermo Pascual
Perez, Krzysztof Z Pietrzak, Michael Walter, and Michelle X Yeo. “Inverse-Sybil
Attacks in Automated Contact Tracing.” In Topics in Cryptology – CT-RSA 2021,
12704:399–421. Springer Nature, 2021. https://doi.org/10.1007/978-3-030-75539-3_17.
ieee: B. Auerbach et al., “Inverse-Sybil attacks in automated contact tracing,”
in Topics in Cryptology – CT-RSA 2021, Virtual Event, 2021, vol. 12704,
pp. 399–421.
ista: 'Auerbach B, Chakraborty S, Klein K, Pascual Perez G, Pietrzak KZ, Walter
M, Yeo MX. 2021. Inverse-Sybil attacks in automated contact tracing. Topics in
Cryptology – CT-RSA 2021. CT-RSA: Cryptographers’ Track at the RSA Conference,
LNCS, vol. 12704, 399–421.'
mla: Auerbach, Benedikt, et al. “Inverse-Sybil Attacks in Automated Contact Tracing.”
Topics in Cryptology – CT-RSA 2021, vol. 12704, Springer Nature, 2021,
pp. 399–421, doi:10.1007/978-3-030-75539-3_17.
short: B. Auerbach, S. Chakraborty, K. Klein, G. Pascual Perez, K.Z. Pietrzak, M.
Walter, M.X. Yeo, in:, Topics in Cryptology – CT-RSA 2021, Springer Nature, 2021,
pp. 399–421.
conference:
end_date: 2021-05-20
location: Virtual Event
name: 'CT-RSA: Cryptographers’ Track at the RSA Conference'
start_date: 2021-05-17
date_created: 2021-08-08T22:01:30Z
date_published: 2021-05-11T00:00:00Z
date_updated: 2023-02-23T14:09:56Z
day: '11'
department:
- _id: KrPi
- _id: GradSch
doi: 10.1007/978-3-030-75539-3_17
ec_funded: 1
intvolume: ' 12704'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2020/670
month: '05'
oa: 1
oa_version: Submitted Version
page: 399-421
project:
- _id: 2564DBCA-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '665385'
name: International IST Doctoral Program
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: Topics in Cryptology – CT-RSA 2021
publication_identifier:
eissn:
- '16113349'
isbn:
- '9783030755386'
issn:
- '03029743'
publication_status: published
publisher: Springer Nature
quality_controlled: '1'
scopus_import: '1'
status: public
title: Inverse-Sybil attacks in automated contact tracing
type: conference
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 12704
year: '2021'
...
---
_id: '7411'
abstract:
- lang: eng
text: "Proofs of sequential work (PoSW) are proof systems where a prover, upon receiving
a statement χ and a time parameter T computes a proof ϕ(χ,T) which is efficiently
and publicly verifiable. The proof can be computed in T sequential steps, but
not much less, even by a malicious party having large parallelism. A PoSW thus
serves as a proof that T units of time have passed since χ\r\n\r\nwas received.\r\n\r\nPoSW
were introduced by Mahmoody, Moran and Vadhan [MMV11], a simple and practical
construction was only recently proposed by Cohen and Pietrzak [CP18].\r\n\r\nIn
this work we construct a new simple PoSW in the random permutation model which
is almost as simple and efficient as [CP18] but conceptually very different. Whereas
the structure underlying [CP18] is a hash tree, our construction is based on skip
lists and has the interesting property that computing the PoSW is a reversible
computation.\r\nThe fact that the construction is reversible can potentially be
used for new applications like constructing proofs of replication. We also show
how to “embed” the sloth function of Lenstra and Weselowski [LW17] into our PoSW
to get a PoSW where one additionally can verify correctness of the output much
more efficiently than recomputing it (though recent constructions of “verifiable
delay functions” subsume most of the applications this construction was aiming
at)."
alternative_title:
- LNCS
article_processing_charge: No
author:
- first_name: Hamza M
full_name: Abusalah, Hamza M
id: 40297222-F248-11E8-B48F-1D18A9856A87
last_name: Abusalah
- 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
- first_name: Michael
full_name: Walter, Michael
id: 488F98B0-F248-11E8-B48F-1D18A9856A87
last_name: Walter
orcid: 0000-0003-3186-2482
citation:
ama: 'Abusalah HM, Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. Reversible
proofs of sequential work. In: Advances in Cryptology – EUROCRYPT 2019.
Vol 11477. Springer International Publishing; 2019:277-291. doi:10.1007/978-3-030-17656-3_10'
apa: 'Abusalah, H. M., Kamath Hosdurg, C., Klein, K., Pietrzak, K. Z., & Walter,
M. (2019). Reversible proofs of sequential work. In Advances in Cryptology
– EUROCRYPT 2019 (Vol. 11477, pp. 277–291). Darmstadt, Germany: Springer International
Publishing. https://doi.org/10.1007/978-3-030-17656-3_10'
chicago: Abusalah, Hamza M, Chethan Kamath Hosdurg, Karen Klein, Krzysztof Z Pietrzak,
and Michael Walter. “Reversible Proofs of Sequential Work.” In Advances in
Cryptology – EUROCRYPT 2019, 11477:277–91. Springer International Publishing,
2019. https://doi.org/10.1007/978-3-030-17656-3_10.
ieee: H. M. Abusalah, C. Kamath Hosdurg, K. Klein, K. Z. Pietrzak, and M. Walter,
“Reversible proofs of sequential work,” in Advances in Cryptology – EUROCRYPT
2019, Darmstadt, Germany, 2019, vol. 11477, pp. 277–291.
ista: Abusalah HM, Kamath Hosdurg C, Klein K, Pietrzak KZ, Walter M. 2019. Reversible
proofs of sequential work. Advances in Cryptology – EUROCRYPT 2019. International
Conference on the Theory and Applications of Cryptographic Techniques, LNCS, vol.
11477, 277–291.
mla: Abusalah, Hamza M., et al. “Reversible Proofs of Sequential Work.” Advances
in Cryptology – EUROCRYPT 2019, vol. 11477, Springer International Publishing,
2019, pp. 277–91, doi:10.1007/978-3-030-17656-3_10.
short: H.M. Abusalah, C. Kamath Hosdurg, K. Klein, K.Z. Pietrzak, M. Walter, in:,
Advances in Cryptology – EUROCRYPT 2019, Springer International Publishing, 2019,
pp. 277–291.
conference:
end_date: 2019-05-23
location: Darmstadt, Germany
name: International Conference on the Theory and Applications of Cryptographic Techniques
start_date: 2019-05-19
date_created: 2020-01-30T09:26:14Z
date_published: 2019-04-24T00:00:00Z
date_updated: 2023-09-06T15:26:06Z
day: '24'
department:
- _id: KrPi
doi: 10.1007/978-3-030-17656-3_10
ec_funded: 1
external_id:
isi:
- '000483516200010'
intvolume: ' 11477'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2019/252
month: '04'
oa: 1
oa_version: Submitted Version
page: 277-291
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: Advances in Cryptology – EUROCRYPT 2019
publication_identifier:
eissn:
- 1611-3349
isbn:
- '9783030176556'
- '9783030176563'
issn:
- 0302-9743
publication_status: published
publisher: Springer International Publishing
quality_controlled: '1'
scopus_import: '1'
status: public
title: Reversible proofs of sequential work
type: conference
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
volume: 11477
year: '2019'
...
---
_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:10.1007/978-3-030-17259-6_11'
apa: 'Fuchsbauer, G., Kamath Hosdurg, C., Klein, K., & 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. https://doi.org/10.1007/978-3-030-17259-6_11'
chicago: Fuchsbauer, Georg, Chethan Kamath Hosdurg, Karen Klein, and Krzysztof Z
Pietrzak. “Adaptively Secure Proxy Re-Encryption,” 11443:317–46. Springer Nature,
2019. https://doi.org/10.1007/978-3-030-17259-6_11.
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. Adaptively Secure Proxy Re-Encryption. Vol.
11443, Springer Nature, 2019, pp. 317–46, doi:10.1007/978-3-030-17259-6_11.
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'
...
---
_id: '193'
abstract:
- lang: eng
text: 'We show attacks on five data-independent memory-hard functions (iMHF) that
were submitted to the password hashing competition (PHC). Informally, an MHF is
a function which cannot be evaluated on dedicated hardware, like ASICs, at significantly
lower hardware and/or energy cost than evaluating a single instance on a standard
single-core architecture. Data-independent means the memory access pattern of
the function is independent of the input; this makes iMHFs harder to construct
than data-dependent ones, but the latter can be attacked by various side-channel
attacks. Following [Alwen-Blocki''16], we capture the evaluation of an iMHF as
a directed acyclic graph (DAG). The cumulative parallel pebbling complexity of
this DAG is a measure for the hardware cost of evaluating the iMHF on an ASIC.
Ideally, one would like the complexity of a DAG underlying an iMHF to be as close
to quadratic in the number of nodes of the graph as possible. Instead, we show
that (the DAGs underlying) the following iMHFs are far from this bound: Rig.v2,
TwoCats and Gambit each having an exponent no more than 1.75. Moreover, we show
that the complexity of the iMHF modes of the PHC finalists Pomelo and Lyra2 have
exponents at most 1.83 and 1.67 respectively. To show this we investigate a combinatorial
property of each underlying DAG (called its depth-robustness. By establishing
upper bounds on this property we are then able to apply the general technique
of [Alwen-Block''16] for analyzing the hardware costs of an iMHF.'
acknowledgement: Leonid Reyzin was supported in part by IST Austria and by US NSF
grants 1012910, 1012798, and 1422965; this research was performed while he was visiting
IST Austria.
article_processing_charge: No
author:
- first_name: Joel F
full_name: Alwen, Joel F
id: 2A8DFA8C-F248-11E8-B48F-1D18A9856A87
last_name: Alwen
- first_name: Peter
full_name: Gazi, Peter
last_name: Gazi
- 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: Georg F
full_name: Osang, Georg F
id: 464B40D6-F248-11E8-B48F-1D18A9856A87
last_name: Osang
orcid: 0000-0002-8882-5116
- first_name: Krzysztof Z
full_name: Pietrzak, Krzysztof Z
id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
last_name: Pietrzak
orcid: 0000-0002-9139-1654
- first_name: Lenoid
full_name: Reyzin, Lenoid
last_name: Reyzin
- first_name: Michal
full_name: Rolinek, Michal
id: 3CB3BC06-F248-11E8-B48F-1D18A9856A87
last_name: Rolinek
- first_name: Michal
full_name: Rybar, Michal
id: 2B3E3DE8-F248-11E8-B48F-1D18A9856A87
last_name: Rybar
citation:
ama: 'Alwen JF, Gazi P, Kamath Hosdurg C, et al. On the memory hardness of data
independent password hashing functions. In: Proceedings of the 2018 on Asia
Conference on Computer and Communication Security. ACM; 2018:51-65. doi:10.1145/3196494.3196534'
apa: 'Alwen, J. F., Gazi, P., Kamath Hosdurg, C., Klein, K., Osang, G. F., Pietrzak,
K. Z., … Rybar, M. (2018). On the memory hardness of data independent password
hashing functions. In Proceedings of the 2018 on Asia Conference on Computer
and Communication Security (pp. 51–65). Incheon, Republic of Korea: ACM. https://doi.org/10.1145/3196494.3196534'
chicago: Alwen, Joel F, Peter Gazi, Chethan Kamath Hosdurg, Karen Klein, Georg F
Osang, Krzysztof Z Pietrzak, Lenoid Reyzin, Michal Rolinek, and Michal Rybar.
“On the Memory Hardness of Data Independent Password Hashing Functions.” In Proceedings
of the 2018 on Asia Conference on Computer and Communication Security, 51–65.
ACM, 2018. https://doi.org/10.1145/3196494.3196534.
ieee: J. F. Alwen et al., “On the memory hardness of data independent password
hashing functions,” in Proceedings of the 2018 on Asia Conference on Computer
and Communication Security, Incheon, Republic of Korea, 2018, pp. 51–65.
ista: 'Alwen JF, Gazi P, Kamath Hosdurg C, Klein K, Osang GF, Pietrzak KZ, Reyzin
L, Rolinek M, Rybar M. 2018. On the memory hardness of data independent password
hashing functions. Proceedings of the 2018 on Asia Conference on Computer and
Communication Security. ASIACCS: Asia Conference on Computer and Communications
Security , 51–65.'
mla: Alwen, Joel F., et al. “On the Memory Hardness of Data Independent Password
Hashing Functions.” Proceedings of the 2018 on Asia Conference on Computer
and Communication Security, ACM, 2018, pp. 51–65, doi:10.1145/3196494.3196534.
short: J.F. Alwen, P. Gazi, C. Kamath Hosdurg, K. Klein, G.F. Osang, K.Z. Pietrzak,
L. Reyzin, M. Rolinek, M. Rybar, in:, Proceedings of the 2018 on Asia Conference
on Computer and Communication Security, ACM, 2018, pp. 51–65.
conference:
end_date: 2018-06-08
location: Incheon, Republic of Korea
name: 'ASIACCS: Asia Conference on Computer and Communications Security '
start_date: 2018-06-04
date_created: 2018-12-11T11:45:07Z
date_published: 2018-06-01T00:00:00Z
date_updated: 2023-09-13T09:13:12Z
day: '01'
department:
- _id: KrPi
- _id: HeEd
- _id: VlKo
doi: 10.1145/3196494.3196534
ec_funded: 1
external_id:
isi:
- '000516620100005'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2016/783
month: '06'
oa: 1
oa_version: Submitted Version
page: 51 - 65
project:
- _id: 25FBA906-B435-11E9-9278-68D0E5697425
call_identifier: FP7
grant_number: '616160'
name: 'Discrete Optimization in Computer Vision: Theory and Practice'
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication: Proceedings of the 2018 on Asia Conference on Computer and Communication
Security
publication_status: published
publisher: ACM
publist_id: '7723'
quality_controlled: '1'
scopus_import: '1'
status: public
title: On the memory hardness of data independent password hashing functions
type: conference
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
year: '2018'
...
---
_id: '637'
abstract:
- lang: eng
text: For many cryptographic primitives, it is relatively easy to achieve selective
security (where the adversary commits a-priori to some of the choices to be made
later in the attack) but appears difficult to achieve the more natural notion
of adaptive security (where the adversary can make all choices on the go as the
attack progresses). A series of several recent works shows how to cleverly achieve
adaptive security in several such scenarios including generalized selective decryption
(Panjwani, TCC ’07 and Fuchsbauer et al., CRYPTO ’15), constrained PRFs (Fuchsbauer
et al., ASIACRYPT ’14), and Yao garbled circuits (Jafargholi and Wichs, TCC ’16b).
Although the above works expressed vague intuition that they share a common technique,
the connection was never made precise. In this work we present a new framework
that connects all of these works and allows us to present them in a unified and
simplified fashion. Moreover, we use the framework to derive a new result for
adaptively secure secret sharing over access structures defined via monotone circuits.
We envision that further applications will follow in the future. Underlying our
framework is the following simple idea. It is well known that selective security,
where the adversary commits to n-bits of information about his future choices,
automatically implies adaptive security at the cost of amplifying the adversary’s
advantage by a factor of up to 2n. However, in some cases the proof of selective
security proceeds via a sequence of hybrids, where each pair of adjacent hybrids
locally only requires some smaller partial information consisting of m ≪ n bits.
The partial information needed might be completely different between different
pairs of hybrids, and if we look across all the hybrids we might rely on the entire
n-bit commitment. Nevertheless, the above is sufficient to prove adaptive security,
at the cost of amplifying the adversary’s advantage by a factor of only 2m ≪ 2n.
In all of our examples using the above framework, the different hybrids are captured
by some sort of a graph pebbling game and the amount of information that the adversary
needs to commit to in each pair of hybrids is bounded by the maximum number of
pebbles in play at any point in time. Therefore, coming up with better strategies
for proving adaptive security translates to various pebbling strategies for different
types of graphs.
alternative_title:
- LNCS
author:
- first_name: Zahra
full_name: Jafargholi, Zahra
last_name: Jafargholi
- 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: Ilan
full_name: Komargodski, Ilan
last_name: Komargodski
- first_name: Krzysztof Z
full_name: Pietrzak, Krzysztof Z
id: 3E04A7AA-F248-11E8-B48F-1D18A9856A87
last_name: Pietrzak
orcid: 0000-0002-9139-1654
- first_name: Daniel
full_name: Wichs, Daniel
last_name: Wichs
citation:
ama: 'Jafargholi Z, Kamath Hosdurg C, Klein K, Komargodski I, Pietrzak KZ, Wichs
D. Be adaptive avoid overcommitting. In: Katz J, Shacham H, eds. Vol 10401. Springer;
2017:133-163. doi:10.1007/978-3-319-63688-7_5'
apa: 'Jafargholi, Z., Kamath Hosdurg, C., Klein, K., Komargodski, I., Pietrzak,
K. Z., & Wichs, D. (2017). Be adaptive avoid overcommitting. In J. Katz &
H. Shacham (Eds.) (Vol. 10401, pp. 133–163). Presented at the CRYPTO: Cryptology,
Santa Barbara, CA, United States: Springer. https://doi.org/10.1007/978-3-319-63688-7_5'
chicago: Jafargholi, Zahra, Chethan Kamath Hosdurg, Karen Klein, Ilan Komargodski,
Krzysztof Z Pietrzak, and Daniel Wichs. “Be Adaptive Avoid Overcommitting.” edited
by Jonathan Katz and Hovav Shacham, 10401:133–63. Springer, 2017. https://doi.org/10.1007/978-3-319-63688-7_5.
ieee: 'Z. Jafargholi, C. Kamath Hosdurg, K. Klein, I. Komargodski, K. Z. Pietrzak,
and D. Wichs, “Be adaptive avoid overcommitting,” presented at the CRYPTO: Cryptology,
Santa Barbara, CA, United States, 2017, vol. 10401, pp. 133–163.'
ista: 'Jafargholi Z, Kamath Hosdurg C, Klein K, Komargodski I, Pietrzak KZ, Wichs
D. 2017. Be adaptive avoid overcommitting. CRYPTO: Cryptology, LNCS, vol. 10401,
133–163.'
mla: Jafargholi, Zahra, et al. Be Adaptive Avoid Overcommitting. Edited by
Jonathan Katz and Hovav Shacham, vol. 10401, Springer, 2017, pp. 133–63, doi:10.1007/978-3-319-63688-7_5.
short: Z. Jafargholi, C. Kamath Hosdurg, K. Klein, I. Komargodski, K.Z. Pietrzak,
D. Wichs, in:, J. Katz, H. Shacham (Eds.), Springer, 2017, pp. 133–163.
conference:
end_date: 2017-07-24
location: Santa Barbara, CA, United States
name: 'CRYPTO: Cryptology'
start_date: 2017-07-20
date_created: 2018-12-11T11:47:38Z
date_published: 2017-01-01T00:00:00Z
date_updated: 2023-09-07T13:32:11Z
day: '01'
department:
- _id: KrPi
doi: 10.1007/978-3-319-63688-7_5
ec_funded: 1
editor:
- first_name: Jonathan
full_name: Katz, Jonathan
last_name: Katz
- first_name: Hovav
full_name: Shacham, Hovav
last_name: Shacham
intvolume: ' 10401'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://eprint.iacr.org/2017/515
month: '01'
oa: 1
oa_version: Submitted Version
page: 133 - 163
project:
- _id: 258AA5B2-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '682815'
name: Teaching Old Crypto New Tricks
publication_identifier:
isbn:
- 978-331963687-0
publication_status: published
publisher: Springer
publist_id: '7151'
quality_controlled: '1'
related_material:
record:
- id: '10035'
relation: dissertation_contains
status: public
scopus_import: 1
status: public
title: Be adaptive avoid overcommitting
type: conference
user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87
volume: 10401
year: '2017'
...