2,188 research outputs found
Signcryption schemes with threshold unsigncryption, and applications
The final publication is available at link.springer.comThe goal of a signcryption scheme is to achieve the same functionalities as encryption and signature together, but in a more efficient way than encrypting and signing separately. To increase security and reliability in some applications, the unsigncryption phase can be distributed among a group of users, through a (t, n)-threshold process. In this work we consider this task of threshold unsigncryption, which has received very few attention from the cryptographic literature up to now (maybe surprisingly, due to its potential applications). First we describe in detail the security requirements that a scheme for such a task should satisfy: existential unforgeability and indistinguishability, under insider chosen message/ciphertext attacks, in a multi-user setting. Then we show that generic constructions of signcryption schemes (by combining encryption and signature schemes) do not offer this level of security in the scenario of threshold unsigncryption. For this reason, we propose two new protocols for threshold unsigncryption, which we prove to be secure, one in the random oracle model and one in the standard model. The two proposed schemes enjoy an additional property that can be very useful. Namely, the unsigncryption protocol can be divided in two phases: a first one where the authenticity of the ciphertext is verified, maybe by a single party; and a second one where the ciphertext is decrypted by a subset of t receivers, without using the identity of the sender. As a consequence, the schemes can be used in applications requiring some level of anonymity, such as electronic auctions.Peer ReviewedPostprint (author's final draft
A Practical Set-Membership Proof for Privacy-Preserving NFC Mobile Ticketing
To ensure the privacy of users in transport systems, researchers are working
on new protocols providing the best security guarantees while respecting
functional requirements of transport operators. In this paper, we design a
secure NFC m-ticketing protocol for public transport that preserves users'
anonymity and prevents transport operators from tracing their customers' trips.
To this end, we introduce a new practical set-membership proof that does not
require provers nor verifiers (but in a specific scenario for verifiers) to
perform pairing computations. It is therefore particularly suitable for our
(ticketing) setting where provers hold SIM/UICC cards that do not support such
costly computations. We also propose several optimizations of Boneh-Boyen type
signature schemes, which are of independent interest, increasing their
performance and efficiency during NFC transactions. Our m-ticketing protocol
offers greater flexibility compared to previous solutions as it enables the
post-payment and the off-line validation of m-tickets. By implementing a
prototype using a standard NFC SIM card, we show that it fulfils the stringent
functional requirement imposed by transport operators whilst using strong
security parameters. In particular, a validation can be completed in 184.25 ms
when the mobile is switched on, and in 266.52 ms when the mobile is switched
off or its battery is flat
Still Wrong Use of Pairings in Cryptography
Several pairing-based cryptographic protocols are recently proposed with a
wide variety of new novel applications including the ones in emerging
technologies like cloud computing, internet of things (IoT), e-health systems
and wearable technologies. There have been however a wide range of incorrect
use of these primitives. The paper of Galbraith, Paterson, and Smart (2006)
pointed out most of the issues related to the incorrect use of pairing-based
cryptography. However, we noticed that some recently proposed applications
still do not use these primitives correctly. This leads to unrealizable,
insecure or too inefficient designs of pairing-based protocols. We observed
that one reason is not being aware of the recent advancements on solving the
discrete logarithm problems in some groups. The main purpose of this article is
to give an understandable, informative, and the most up-to-date criteria for
the correct use of pairing-based cryptography. We thereby deliberately avoid
most of the technical details and rather give special emphasis on the
importance of the correct use of bilinear maps by realizing secure
cryptographic protocols. We list a collection of some recent papers having
wrong security assumptions or realizability/efficiency issues. Finally, we give
a compact and an up-to-date recipe of the correct use of pairings.Comment: 25 page
Efficient and Low-Cost RFID Authentication Schemes
Security in passive resource-constrained Radio Frequency Identification
(RFID) tags is of much interest nowadays. Resistance against illegal tracking,
cloning, timing, and replay attacks are necessary for a secure RFID
authentication scheme. Reader authentication is also necessary to thwart any
illegal attempt to read the tags. With an objective to design a secure and
low-cost RFID authentication protocol, Gene Tsudik proposed a timestamp-based
protocol using symmetric keys, named YA-TRAP*. Although YA-TRAP* achieves its
target security properties, it is susceptible to timing attacks, where the
timestamp to be sent by the reader to the tag can be freely selected by an
adversary. Moreover, in YA-TRAP*, reader authentication is not provided, and a
tag can become inoperative after exceeding its pre-stored threshold timestamp
value. In this paper, we propose two mutual RFID authentication protocols that
aim to improve YA-TRAP* by preventing timing attack, and by providing reader
authentication. Also, a tag is allowed to refresh its pre-stored threshold
value in our protocols, so that it does not become inoperative after exceeding
the threshold. Our protocols also achieve other security properties like
forward security, resistance against cloning, replay, and tracking attacks.
Moreover, the computation and communication costs are kept as low as possible
for the tags. It is important to keep the communication cost as low as possible
when many tags are authenticated in batch-mode. By introducing aggregate
function for the reader-to-server communication, the communication cost is
reduced. We also discuss different possible applications of our protocols. Our
protocols thus capture more security properties and more efficiency than
YA-TRAP*. Finally, we show that our protocols can be implemented using the
current standard low-cost RFID infrastructures.Comment: 21 pages, Journal of Wireless Mobile Networks, Ubiquitous Computing,
and Dependable Applications (JoWUA), Vol 2, No 3, pp. 4-25, 201
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