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2012-08-23
11:07 [Event][New] Workshop on Real-World Cryptography

  From January 9 to January 11
Location: Palo Alto, United States
More Information: https://crypto.stanford.edu/RealWorldCrypto/index.php


11:07 [Event][New] WCC 2013: International Workshop on Coding and Cryptography

  Submission: 21 December 2012
Notification: 1 February 2013
From April 15 to April 19
Location: Bergen, Norway
More Information: http://www.selmer.uib.no/WCC2013/


11:06 [Event][New] ANTE: Annals of Telecommunications: Special Issue on: Privacy-aware electronic so

  Submission: 1 October 2012
From July 1 to December 31
More Information: http://www-public.it-sudparis.eu/~lauren_m/Special-Issue/CfP_privacy_aware_electronic_society-2012.pdf


00:17 [Pub][ePrint] Cryptanalysis of Two Dynamic ID-based Remote User Authentication Schemes for Multi-Server Architecture, by Ding Wang, Chun-guang Ma, De-li Gu and Zhen-shan Cui

  Understanding security failures of cryptographic protocols is the key to both patching existing protocols and designing future schemes. In NSS\'10, Shao and Chin showed that Hsiang and Shih\'s dynamic ID-based remote user authentication scheme for multi-server environment is vulnerable to server spoofing attack and fails to preserve user anonymity, and further proposed an improved version which is claimed to be efficient and secure. In this study, however, we will demonstrate that, although Shao-Chin\'s scheme possesses many attractive features, it still cannot achieve the claimed security goals, and we report its following flaws: (1) It cannot withstand offline password guessing attack under their non-tamper resistance assumption of the smart card; (2) It fails to provide user anonymity; (3) It is prone to user impersonation attack. More recently, Li et al. found that Sood et al.\'s dynamic ID-based authentication protocol for multi-server architecture is still vulnerable to several kinds of attacks and presented a new scheme that attempts to overcome the identified weaknesses. Notwithstanding their intentions, Li et al.\'s scheme is still found vulnerable to various known attacks by researchers. In this study, we perform a further cryptanalysis and uncover its two other vulnerabilities: (1) It cannot achieve user anonymity, the essential goal of a dynamic ID-based scheme; (2) It is susceptible to offline password guessing attack. The proposed cryptanalysis discourages any use of the two schemes under investigation in practice and reveals some subtleties and challenges in designing this type of schemes.



00:17 [Pub][ePrint] Exploiting Collisions in Addition Chain-based Exponentiation Algorithms, by Neil Hanley and HeeSeok Kim and Michael Tunstall

  Public key cryptographic algorithms are typically based on group exponentiation algorithms, and many algorithms have been proposed in the literature based on addition chains. We describe attacks based on collisions of variables manipulated in group operations extending attacks described in the literature. The advantage of our attacks over previous work is that the attacks can be applied to a single trace and do not require any knowledge of the input to the exponentiation algorithm. Moreover, we prove that our attacks are applicable to all addition chain-based exponentiation algorithms. This means that a side channel resistant implementation of a group exponentiation will require countermeasures that introduce enough noise that an attack is not practical.



00:17 [Pub][ePrint] Computational Soundness without Protocol Restrictions, by Michael Backes and Ankit Malik and Dominique Unruh

  The abstraction of cryptographic operations by term algebras, called

Dolev-Yao models, is essential in almost all tool-supported methods

for verifying security protocols. Recently significant progress was

made in establishing computational soundness results: these results

prove that Dolev-Yao style models can be sound with respect to actual

cryptographic realizations and security definitions. However, these

results came at the cost of imposing various constraints on the set of

permitted security protocols: e.g., dishonestly generated keys must

not be used, key cycles need to be avoided, and many more. In a

nutshell, the cryptographic security definitions did not adequately

capture these cases, but were considered carved in stone; in contrast,

the symbolic abstractions were bent to reflect cryptographic features

and idiosyncrasies, thereby requiring adaptations of existing

verification tools.

In this paper, we pursue the opposite direction: we consider a

symbolic abstraction for public-key encryption and identify two

cryptographic definitions called PROG-KDM (programmable key-dependent

message) security and MKE (malicious-key extractable) security that we

jointly prove to be sufficient for obtaining computational soundness

without imposing assumptions on the protocols using this

abstraction. In particular, dishonestly generated keys obtained from

the adversary can be sent, received, and used. The definitions can be

met by existing cryptographic schemes in the random oracle model. This

yields the first computational soundness result for trace-properties

that holds for arbitrary protocols using this abstraction (in

particular permitting to send and receive dishonestly generated keys),

and that is accessible to all existing tools for reasoning about

Dolev-Yao models without further adaptations.



00:17 [Pub][ePrint] Short communication: An interpretation of the Linux entropy estimator, by Benjamin Pousse

  The Linux random number generator (LRNG) aims to produce random numbers with all the limitations due to a deterministic machine. Two recent analysis exist for this generator. These analysis provide strong cryptographic details about LRNG. However both fail to give a mathematical explanation of the entropy estimator embedded. In this paper we propose an interpretation using Newton polynomial interpolation.



00:17 [Pub][ePrint] Designated Verifier Threshold Proxy Signature Scheme without Random Oracles, by Mohammad Beheshti-Atashgah \\and Majid Bayat \\and Mahmoud Gardeshi \\and Mohammad Reza Aref

  In a $(t,n)$ designated verifier threshold proxy signature \\, scheme, an original signer can delegate his/her signing power to $n$ proxy signers such that any $t$ or more out of $n$ proxy signers can sign messages on behalf of the original signer but $t-1$ or less of the proxy signers cannot generate a valid proxy signature. Of course, the signature is issued for a designated receiver and therefore only the designated receiver can validate the proxy signature. In this paper, we propose a new designated verifier threshold proxy signature scheme and also show that the proposed scheme has provable security in the standard model. The security of proposed scheme is based on the $GBDH$ assumption and the proposed scheme satisfies all the security requirements of threshold proxy signature schemes.



00:17 [Pub][ePrint] Recursive Linear and Differential Cryptanalysis of Ultralightweight Authentication Protocols, by Zahra Ahmadian, Mahmoud Salmasizadeh, Mohammad Reza Aref

  Privacy is faced to serious challenges in the ubiquitous computing world. In order to handle this problem, some researches in recent years have focused on design and analysis of privacy friendly ultralightweight authentication protocols. In less than a decade, many ultralightweight authentication protocols are proposed. Though, successful crypanalyses are proposed for almost all of them, most of these attacks are based on ad-hoc methods that are not extensible to a large class of ultralightweight protocols. So this research area still suffers from the lack of structured cryptanalysis and evaluation ethods.

In this paper, we introduce new frameworks for full disclosure attacks on ultralightweight authentication protocols based on new concepts of recursive linear and recursive differential cryptanalysis. Both of them exploit triangular functions in ultralightweight protocols and recover all secret data stored in the tag in a recursive manner. The recursive linear attack is applied to Yeh et al. and SLMAP authentication protocols. This attack is passive, deterministic (i.e. the attacker can retrieve all the secrets with probability of one), and requires only a single authentication session. The recursive differential attack is more powerful and can be applied to the protocols which linear attack may not work on. We show the effectiveness of this attack on LMAP++and SASI authentication protocols. This differential attack is probabilistic, active in the sense that the attacker suffices only to block some specific messages, and requires a few authentication sessions.





2012-08-22
00:17 [Pub][ePrint] A j-lanes tree hashing mode and j-lanes SHA-256, by Shay Gueron

  j-lanes hashing is a tree mode that splits an input message to j slices, computes j independent digests of each slice, and outputs the hash value of their concatenation. We demonstrate the performance advantage of j-lanes hashing on SIMD architectures, by coding a 4-lanes-SHA-256 implementation and measuring its performance on the latest 3rd Generation Intel® Core(TM). For message ranging 2KB to 132KB in length, the 4-lanes SHA-256 is between 1.5 to 1.97 times faster than the fastest publicly available implementation (that we are aware of), and between 1.9 to 2.5 times faster than OpenSSL 1.0.1c. For long messages, there is no significant performance difference between different choices of j. We show that the 4-lanes SHA-256 is faster than the two SHA3 finalists (BLAKE and Keccak) that have a published tree mode implementation. We explain why j-lanes hashing will be even faster on the future AVX2 architecture with 256 bits registers. This suggests that standardizing a tree mode for hash functions (SHA-256 in particular) would deliver significant performance benefits for a multitude of algorithms and usages.



00:17 [Pub][ePrint] Improved Key Recovery Attacks on Reduced-Round AES in the Single-Key Setting, by Patrick Derbez and Pierre-Alain Fouque and Jérémy Jean

  In this paper, we revisit meet-in-the-middle attacks on AES in the

single-key model and improve on Dunkelman, Keller and Shamir attacks

of Asiacrypt 2010. We present the best attack on 7 rounds of AES-128

where data/time/memory complexities are below $2^{100}$. Moreover, we

are able to extend the number of rounds to reach attacks on 8 rounds

for both AES-192 and AES-256. This gives the best attacks on those two

versions with a data complexity of $2^{107}$ chosen-plaintexts, a

memory complexity of $2^{96}$ and a time complexity of $2^{172}$ for

AES-192 and $2^{196}$ for AES-256. Finally, we also describe the best

attack on 9 rounds of AES-256 with $2^{120}$ chosen-plaintexts and

time and memory complexities of $2^{203}$. All these attacks have been

found by carefully studying the number of reachable multisets in

Dunkelman et al. attacks.