International Association for Cryptologic Research

# IACR News Central

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2014-04-22
00:17 [Pub][ePrint]

This paper designed a new extended chaotic map-based Identity-based encryption (ECM-IBE) scheme and Identity-based digital signature (ECM-IDS) scheme using extended chaotic maps. The security of the ECM-IBE scheme is based on the hardness assumption of chaotic maps-based decisional Diffie-Hellman (CDDH) problem, whereas the ECM-IDS scheme is secure based on the difficulties of chaotic maps-based discrete logarithm (CDL) problem.

00:17 [Pub][ePrint]

Inspired from the Identity-based cryptosystem proposed by Adi Shamir, and Boneh and Franklin, this paper designed a new Identity-based digital signature (ECM-IDS) scheme using extended chaotic maps. The ECM-IDS scheme is secure based on the difficulties of integer factorization problem.

00:17 [Pub][ePrint]

By combining the time-memory-data tradeoff (TMDTO) attack independently proposed by Babbage and Goli\\\'{c} (BG) with the BSW sampling technique, this paper explores to mount a new TMDTO attack on stream ciphers. The new attack gives a wider variety of trade-offs, compared with original BG-TMDTO attack. It is efficient when multiple data is allowed for the attacker from the same key with different IVs, even though the internal state size is twice the key size. We apply the new attack to MICKEY and Grain stream ciphers, and improves the existing TMDTO attacks on them. Our attacks on Grain v1 and Grain-128 stream ciphers are rather attractive in the respect that the online time, offline time and memory complexities are all better than an exhaustive key search, and the amount of keystream needed are completely valid. Finally, we generalize the new attack to a Guess and Determine-TMDTO attack on stream ciphers, and mount a Guess and Determine-TMDTO attack on SOSEMANUK stream cipher with the online time and offline time complexities both equal to $2^{128}$, which achieves the best time complexity level compared with all existing attacks on SOSEMANUK so far.

2014-04-21
21:17 [Pub][ePrint]

In 2013, the US National Security Agency proposed two new families of lightweight block ciphers: SIMON and SPECK. However, no security analysis was provided for these ciphers. Currently, linear and differential cryptanalytic results for SIMON ciphers are available in the literature, but no fault attacks on these two cipher families have been reported so far. In this paper, we present the first fault attack on SIMON and SPECK families. The attack assumes a fault model that can flip only one bit of the intermediate result. Using this attack the n-bit secret key used in SIMON cipher can be recovered using (n/2) bit faults on an average while the n-bit secret key of SPECK cipher can be recovered using (n/3) bit faults. Furthermore, we demonstrate a more practical attack on SIMON that employs a random byte fault model. This attack retrieves multiple bits of the key depending upon the Hamming weight of the byte fault. The average number of byte faults required to retrieve all n bits of the last round key is (n/8).

21:17 [Pub][ePrint]

In this paper, we present a new bit-parallel Montgomery multiplier for $GF(2^m)$ generated with irreducible trinomials. A newly proposed divide-and-conquer approach is applied to simplify the polynomial multiplication while the Montgomery squaring is induced to simplify the modular reduction. Meanwhile, this design effectively exploits the overlapped elements in squaring and reduction operation to reduce the space complexity. As a result, the proposed multiplier has about 25\\% reduced space complexity compared with previous multipliers, with a slight increase of time complexity. Among five binary fields recommended by NIST for the ECDSA (Elliptic Curve Digital Signature Algorithm), there exist two fields, i.e., $GF(2^{409})$, $GF(2^{233})$,

defined by trinomials. For these two fields, we show that our proposal outperforms the previous best known results if the space and time complexities are both considered.

21:17 [Pub][ePrint]

In this paper, we show two new constructions of chosen ciphertext secure (CCA secure) public key encryption (PKE) from general assumptions. The key ingredient in our constructions is an obfuscator for point functions with multi-bit output (MBPF obfuscators, for short), that satisfies some (average-case) indistinguishability-based security, which we call AIND security, in the presence of hard-to-invert auxiliary input. Specifically, our first construction is based on a chosen plaintext secure PKE scheme and an MBPF obfuscator satisfying the AIND security in the presence of computationally hard-to-invert auxiliary input. Our second construction is based on a lossy encryption scheme and an MBPF obfuscator satisfying the AIND security in the presence of statistically hard-to-invert auxiliary input. To clarify the relative strength of AIND security, we show the relations among security notions for MBPF obfuscators, and show that AIND security with computationally (resp. statistically) hard-to-invert auxiliary input is implied by the average-case virtual black-box (resp. virtual grey-box) property with the same type of auxiliary input. Finally, we show that a lossy encryption scheme can be constructed from an obfuscator for point functions (point obfuscator) that satisfies re-randomizability and a weak form of composability in the worst-case virtual grey-box sense. This result, combined with our second generic construction and several previous results on point obfuscators and MBPF obfuscators, yields a CCA secure PKE scheme that is constructed \\emph{solely} from a re-randomizable and composable point obfuscator. We believe that our results make an interesting bridge that connects CCA secure PKE and program obfuscators, two seemingly isolated but important cryptographic primitives in the area of cryptography.

21:17 [Pub][ePrint]

We present a new protocol for maliciously secure two-partycomputation based on cut-and-choose of garbled circuits using the recent idea of forge-and-loose\'\' which eliminates around a factor 3 of garbled circuits that needs to be constructed and evaluated. Our protocol introduces a new way to realize the \"forge-and-loose\" approach which avoids an auxiliary secure two-party computation protocol, does not rely on any number theoretic assumptions and parallelizes well in a same instruction, multiple data (SIMD) framework.

With this approach we prove our protocol universally composable-secure against a malicious adversary assuming access to oblivious transfer, commitment and coin-tossing functionalities in the random oracle model.

Finally, we construct, and benchmark, a SIMD implementation of this protocol using a GPU as a massive SIMD device. The findings compare favorably with all previous implementations of maliciously secure, two-party computation.

21:17 [Pub][ePrint]

Authenticated encryption algorithms protect both the confidentiality and integrity of messages with a single processing pass. We show how to utilize the $L \\circ P \\circ S$ transform of the Russian GOST R 34.11-2012 standard hash Streebog\'\' to build an efficient, lightweight algorithm for Authenticated Encryption with Associated Data (AEAD) via the Sponge construction. The proposed algorithm StriBob\'\' has attractive security properties, is faster than the Streebog hash alone, twice as fast as the GOST 28147-89 encryption algorithm, and requires only a modest amount of running-time memory. StriBob is a Round 1 candidate in the CAESAR competition.

2014-04-20
18:17 [Pub][ePrint]

Basing on the original Cube attack, this paper proposes an improved method of Cube attack on stream ciphers, which makes improvement on the pre-processing phase of the original attack. The new method can induce maxterms of higher-order from those of lower-order by the trade-off between time and space, thus recovering more key bits and reducing the search complexity on higher-dimension. In this paper, the improved attack is applied to Lili-128 algorithm and reduced variants of Trivium algorithm. We can recover 88 key bits of Lili-128 algorithm within time complexity of 2^14 and 48 key bits of Trivium algorithm can be recovered by cubes with dimension no larger than 8 when the initialization round is 576, the results are much better than those of the original attacks.

18:17 [Pub][ePrint]

The fully homomorphic symmetric encryption scheme \\emph{MORE} encrypts

keys by conjugation with a random invertible matrix over an RSA modulus.

We provide a two known-ciphertexts cryptanalysis recovering a linear dependence among

the two encrypted keys.

18:17 [Pub][ePrint]

We present attacks against CMCC that invalidate the claimed security of integrity protection and misuse resistance. We exploit the fact zero-padding is used on both the message and authenticated data and demonstrate how one may generate a forgery with a single call to the encryption oracle. From this we calculate the ciphertext of the chosen message, yielding a forgery and so breaking INT-CTXT. In the nonce-reuse setting, existence of a forgery leads directly to a 2-query distinguisher.