International Association for Cryptologic Research

# IACR News Central

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Further sources to find out about changes are CryptoDB, ePrint RSS, ePrint Web, Event calender (iCal).

2012-07-16
03:17 [Pub][ePrint]

We present a generalized learning with errors (LWE) problem, which is essentially a simple and direct extension of the original LWE problem to the case of matrices.

Then we use this new version of LWE problem, which we call matrix LWE problem to build new cryptographic schemes, which include a new scalable key distribution scheme, a new key exchanges scheme and a new simple identity-based encryption scheme.

03:17 [Pub][ePrint]

We introduce the notion of {\\em arithmetic codex}, or {\\em codex} for short.

It encompasses several well-established notions from cryptography (arithmetic secret sharing schemes, i.e., enjoying additive as well as multiplicative properties) and algebraic complexity theory (bilinear complexity of multiplication) in a natural mathematical framework.

Arithmetic secret sharing schemes have important applications to secure multiparty computation and even to {\\em two}-party cryptography. Interestingly, several recent applications to two-party cryptography rely crucially on the existing results on {\\em asymptotically good} families\'\' of suitable such schemes. Moreover, the construction of these schemes requires asymptotically good towers of function fields over finite fields: no elementary (probabilistic) constructions are known in these cases. Besides introducing the notion, we discuss some of the constructions, as well as some limitations.

03:17 [Pub][ePrint]

We present the first wide-strong RFID identification protocol that is based on zero-knowledge. Until now this notion has only been achieved by schemes based on IND-CCA2 encryption. Rigorous proofs in the standard model are provided for the security and privacy properties of our protocol. Furthermore our protocol is the most efficient solution presented in the literature. Using only Elliptic Curve Cryptography (ECC), the required circuit area can be minimized such that our protocol even fits on small RFID tags. Concerning computation on the tag, we only require two scalar-EC point multiplications.

03:17 [Pub][ePrint]

In this paper we propose an efficient and regular ternary algorithm for scalar multiplication on elliptic curves over finite fields of characteristic three.

This method is based on full signed ternary expansion of a scalar to be multiplied. The cost per bit of this algorithm is lower than that of all previous ones.

2012-07-14
07:01 [Job][New]

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2012-07-12
18:17 [Pub][ePrint]

We provide a functional encryption system that supports functionality

for regular languages. In our system a secret key is associated with

a Deterministic Finite Automata (DFA) M. A ciphertext, CT,

encrypts a message m and is associated with an arbitrary length string w. A user is able to decrypt the ciphertext CT if

and only if the DFA M associated with his private key accepts the string w.

Compared with other known functional encryption systems, this is

the first system where the functionality is capable of recognizing an

unbounded language. For example, in (Key-Policy) Attribute-Based

Encryption (ABE) a private key SK is associated with a single

boolean formula which operates over a fixed number of

boolean variables from the ciphertext. In contrast, in our system a

DFA M will meaningfully operate over an arbitrary length input w.

We propose a system that utilizes bilinear groups. Our solution is a

\"public index\" system, where the message m is hidden, but the

string w is not. We prove security in the selective model under a

variant of the decision l-Bilinear Diffie-Hellman Exponent

(BDHE) assumption that we call the decision l-Expanded BDHE problem.

14:03 [Event][New]

From September 3 to September 7
Location: Bochum, Germany

13:01 [Conf][Crypto]

We are excited to announce that for the first time the National Science Foundation (NSF) is offering stipends to students attending CRYPTO!

All students who are currently studying in a US university are eligible to receive support from the NSF. Students in under-represented groups are especially encouraged to apply. Given the new NSF funding, together with existing funding from our industry sponsors, we are now able to award a second round of stipends to student attendees, both *domestic* and *international*.

To apply, you must be a student enrolled in a US or foreign university, and please ask your PhD supervisor or Department Head to email a brief justification to the General Chair (crypto2012@iacr.org) before the new deadline of July 27th, 2012.

2012-07-11
18:17 [Pub][ePrint]

Malicious insider security of authenticated key exchange (AKE) protocol addresses the situation that an AKE protocol is secure even with existing dishonest parties established by adversary in corresponding security experiment. In the eCK model, the $\\EstablishParty$ query is used to model the malicious insider setting. However such strong query is not clearly formalized so far. We show that the proof of possession assumptions for registering public keys are of prime importance to malicious insider security. In contrast to previous schemes, we present an eCK secure protocol in the standard model, without assuming impractical, strong, concurrent zero-knowledge proofs of knowledge of secret keys done to the CA at key registration. The security proof of our scheme is based on standard pairing assumption, collision resistant hash functions, bilinear decision Diffie-Hellman (BDDH) and decision linear Diffie-Hellman (DLIN) assumptions, and pseudo-random functions with pairwise independent random source $\\pi\\prf$.\\\\

18:17 [Pub][ePrint]

We extend the work of Bellare, Boldyreva and Staddon on the systematic analysis of randomness reuse to construct multi-recipient

encryption schemes to the case where randomness is reused across different cryptographic primitives. We find that through the additional binding introduced through randomness reuse, one can actually obtain a security amplification with respect to the standard black-box compositions, and achieve a stronger level of security. We introduce stronger notions of security for encryption and signatures,

where challenge messages can depend in a restricted way on the random coins used in encryption, and show that two variants of the KEM/DEM paradigm give rise to encryption schemes that meet this enhanced notion of security. We obtain a very efficient signcryption scheme that is

secure against insider attackers without random oracles.

18:17 [Pub][ePrint]

In this paper, we revisit formalizations of information-theoretic security for symmetric-key encryption and key agreement protocols. In general, we can formalize information-theoretic security in various ways: some of them can be formalized as stand-alone security by extending (or relaxing) Shannon\'s perfect secrecy; some of them can be done based on composable security. Then, a natural question about this is: what is the gap between the formalizations? To answer the question, we investigate relationships between several formalizations of information-theoretic security for symmetric-key encryption and key agreement protocols. Specifically, for symmetric-key encryption protocols which may have decryption-errors, we deal with the following formalizations of security: formalizations extended (or relaxed) from Shannon\'s perfect secrecy by using mutual information and statistical distance; information-theoretic analogue of indistinguishability by Goldwasser and Micali; and the ones of composable security by Maurer et al. and Canetti. Then, we show that those formalizations are essentially equivalent under both one-time and multiple-use models. Under the both models, we also derive lower bounds of the adversary\'s (or distinguisher\'s) advantage and secret-key size required under all of the above formalizations. Although some of them are already known, we can derive them all at once through our relationships between the formalizations. In addition, we briefly observe impossibility results which easily follow from the lower bounds. The similar results are also shown for key agreement protocols which may have agreement-errors.