International Association for Cryptologic Research

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21:17 [Pub][ePrint] Key-policy Attribute-based Encryption for Boolean Circuits from Bilinear Maps, by Ferucio Laurentiu Tiplea and Constantin Catalin Dragan

  We propose the first Key-policy Attribute-based Encryption (KP-ABE) scheme for (monotone) Boolean circuits based on bilinear maps. The construction is based on secret sharing and just one bilinear map, and can be viewed as an extension of the KP-ABE scheme in [7]. Selective security of the proposed scheme in the standard model is proved, and comparisons with the scheme in [5] based on leveled multilinear maps, are provided. Thus, for Boolean circuits representing multilevel access structures, our KP-ABE scheme is more efficient than the one in [5].

21:17 [Pub][ePrint] SPOKE: Simple Password-Only Key Exchange in the Standard Model, by Michel Abdalla and Fabrice Benhamouda and David Pointcheval

  In this paper, we propose a simple and efficient password-only authenticated key exchange (PAKE) protocol with a proof of security in the standard model. In its most efficient instantiation, the new protocol has only two flows of communication and a total of 7 group elements and its proof of security is based on the plain DDH assumption. To achieve this goal, we first propose a variant of the Gennaro-Lindell/Katz-Ostrovsky-Yung (GL/KOY) PAKE protocol, in which the encryption schemes used to generate the first- and second-flow messages are only required to be semantically secure against plaintext-checking attacks (IND-PCA) and chosen-plaintext attacks (IND-CPA), respectively. Unlike semantic security against chosen-ciphertext attacks (IND-CCA), an IND-PCA adversary is only given access to an oracle which says whether or not a given ciphertext encrypts a given message. Next, we design a more efficient variant of the Cramer-Shoup encryption scheme with shorter ciphertexts together with an associated hash proof system and we prove its IND-PCA security under the plain DDH assumption. We believe that the new IND-PCA scheme is of independent interest, since it yields, in particular, the most efficient IND-CCA encryption scheme under plain DDH for small messages.

15:17 [Pub][ePrint] Recursive Trees for Practical ORAM, by Tarik Moataz and Erik-Oliver Blass and Guevara Noubir

  We present a general construction to reduce the communication cost of recent tree-based ORAMs. Contrary to trees with constant height and path lengths, our new construction r-ORAM provides varying, shorter path lengths. Accessing an element in the ORAM tree will have different communication cost depending on the location of the element. The main idea behind r-ORAM is a recursive ORAM tree structure, where nodes in the tree are roots of other trees. While this approach results in a worst-case access cost (tree height) at most as any recent tree-based ORAM, we demonstrate that the expected cost saving is around 35% for binary tree ORAMs. For a k-ary tree-based ORAM, we still can reduce cost with r-ORAM, e.g., 20% for k =4. Besides reducing communication cost, r-ORAM also reduces storage overhead on the server by 20%. To prove r-ORAM\'s soundness, we conduct a detailed overflow analysis. We stress that r-ORAM is general and can be applied to all recent tree ORAMs, both constant memory or poly-log client memory ORAMs.

06:17 [Pub][ePrint] DTKI: a new formalized PKI with no trusted parties, by Jiangshan Yu and Vincent Cheval and Mark Ryan

  The security of public key validation protocols for web-based applications has recently attracted attention because of weaknesses in the certificate authority model, and consequent attacks.

Recent proposals using public logs have succeeded in making certificate management more transparent and verifiable. How- ever, those proposals involve a fixed set of authorities which create a monopoly, and they have heavy reliance on trusted parties that monitor the logs.

We propose a distributed transparent key infrastructure (DTKI), which greatly reduces the monopoly of service providers and removes the reliance on trusted parties. In addition, this paper formalises the public log data structure and provides a formal analysis of the security that DTKI guarantees.

06:17 [Pub][ePrint] Adaptive versus Static Security in the UC Model, by Ivan Damgård and Jesper Buus Nielsen

  We show that for certain class of unconditionally secure protocols and

target functionalities, static security implies adaptive security in the UC

model. Similar results were previously only known for models with

weaker security and/or composition guarantees. The result is, for

instance, applicable to a wide range of protocols based on secret

sharing. It ``explains\'\' why an often used proof technique for such

protocols works, namely where the simulator runs in its head a copy of

the honest players using dummy inputs and generates a protocol

execution by letting the dummy players interact with the

adversary. When a new player $P_i$ is corrupted, the simulator

adjusts the state of its dummy copy of $P_i$ to be consistent with

the real inputs and outputs of $P_i$ and gives the state to the

adversary. Our result gives a characterisation of the cases where this

idea will work to prove adaptive security. As a special case,

we use our framework to give the first proof of adaptive security

of the seminal BGW protocol in the UC framework.

06:17 [Pub][ePrint] A Cryptographic Study of Tokenization Systems, by Sandra D\\\'iaz-Santiago and Lil Mar\\\'ia Rodr\\\'iguez-Henr\\\'iquez and Debrup Chakraborty

  Payments through cards have become very popular in today\'s world. All businesses now have options to receive payments through this instrument, moreover most organizations store card information of its customers in

some way to enable easy payments in future. Credit card data is a very sensitive information and theft of this data is a serious threat to any company. Any organization that stores credit card data needs to achieve payment card industry (PCI) compliance, which is an intricate process where the organization needs to demonstrate that the data it stores is safe. Recently there has been a paradigm shift in treatment of the problem of storage of payment card information. In this new paradigm instead of the real credit card data a token is stored, this process is called ``tokenization\". The token resembles the

credit/debit card number but is in no way related to it. This solution relieves the merchant from the burden of PCI compliance in several ways.

Though tokenization systems are heavily in use, to our knowledge, a formal cryptographic study of this problem has not yet been done. In this paper we initiate a study in this direction. We formally define the syntax of a tokenization system, and several notions of security for such systems. Finally, we provide some constructions of tokenizers and analyze their security in the light of our definitions.

15:54 [Event][New] Inscrypt 2014: The 10th International Conference on Information Security and Cryptology

  Submission: 31 August 2014
Notification: 7 November 2014
From December 13 to December 15
Location: Beijing, China
More Information:

23:09 [Event][New] WCC 2015: The 9th International Workshop on Coding and Cryptography

  Submission: 19 January 2015
Notification: 2 March 2015
From April 13 to April 17
Location: Paris, France
More Information:

17:28 [Event][New] CT-RSA 2015: RSA Conference 2015 Cryptographers' Track

  Submission: 20 October 2014
Notification: 20 December 2014
From April 20 to April 24
Location: San Francisco, USA
More Information:

16:59 [Job][New] Cryptography Engineer, Nagravision, Cheseaux - Switzerland

  - Conception and definition of cryptographic algorithms (block ciphers, hash functions, asymmetric primitives, protocols)

- Implementation cryptographic primitives and protocols in C/C++/Python languages

- Definitions of related tests for validation

- Definition and implementation of dedicated tools to aid implementation and analysis of cryptographic algorithms

- Work closely with HW design and verification team

- Close collaboration with software teams for system validation

- Working closely with security architects and system architects for definition of requirements

- Follow-up of related academic literature and developments

- Deliver crypto specifications documents to internal teams

- Provide guidance and support to peers in tools and IP design

16:58 [Job][Update] PhD and PostDoc positions in applied cryptography, Radboud University Nijmegen, The Netherlands

  The Digital Security group at the Radboud University Nijmegen invites applications for PhD and PostDoc positions in applied cryptography and embedded security.

The research envisioned is on side-channel cryptanalysis, fault attacks and countermeasures and/or lightweight cryptography (protocols, crypto primitives and implementations).

The project has sufficient funds to support career development, conference visits, summer schools, and similar scientific activities.


For PhD students:

Successful candidates must hold an M.Sc. degree (or equivalent) from the university study of Computer Science, Mathematics or Engineering. Applications from students that are expected to finish their master thesis within 1 year will also be considered. Prior background/experience in cryptography and/or computer security is an asset.

For PostDocs:

Applicants should have a Ph.D. and expertise in at least one of the following research areas:

- applied cryptography

- embedded security

- hardware design for cryptography/cryptanalysis

- side-channel analysis and countermeasures

- machine learning and data mining

We expect proven expertise in your area of research by publications at top conferences and journals, some experience with EU projects, student supervision etc.

Conditions of employment

PhD positions are for 4 years, PostDoc positions are for up to 2 years, the expected starting dates are flexible.

Candidates moving to the Netherlands from abroad may qualify for a tax incentive scheme, where 30% of your income is tax-free.

For additional information, see, and for the positions contact:

Lejla Batina (,