International Association for Cryptologic Research

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2015-02-23
22:17 [Pub][ePrint] Weakening the Isolation Assumption of Tamper-proof Hardware Tokens, by Rafael Dowsley and Jörn Müller-Quade and Tobias Nilges

  Recent results have shown the usefulness of tamper-proof hardware tokens as a setup assumption for building UC-secure two-party computation protocols, thus providing broad security guarantees and allowing the use of such protocols as buildings blocks in the modular design of complex cryptography protocols. All these works have in common that they assume the tokens to be completely isolated from their creator, but this is a strong assumption. In this work we investigate the feasibility of cryptographic protocols in the setting where the isolation of the hardware token is weakened.

We consider two cases: (1) the token can relay messages to its creator, or (2) the creator can send messages to the token after it is sent to the receiver. We provide a detailed characterization for both settings, presenting both impossibilities and information-theoretically secure solutions.



03:08 [PhD][New] Jerzy Jaworski

  Name: Jerzy Jaworski
Category: (no category)



03:08 [PhD][New] Przemyslaw Sokolowski: Contributions to cryptanalysis: design and analysis of cryptographic hash functions

  Name: Przemyslaw Sokolowski
Topic: Contributions to cryptanalysis: design and analysis of cryptographic hash functions
Category: secret-key cryptography

Description:

A cryptographic hash function is a mechanism producing a fixed-length output of a message of arbitrary length. It fulfills a collection of security requirements guaranteeing that a hash function does not introduce any weakness into the system to which it is applied. The example applications of cryptographic hash functions include digital signatures and message authentication codes. This thesis analyzes cryptographic hash functions and studies the design principles in the construction of secure cryptographic hash functions.

We investigate the problem of building hash functions from block ciphers and the security properties of different structures used to design compression functions. We show that we can build open-key differential distinguishers for Crypton, Hierocrypt-3, SAFER++ and Square. We know that our attack on SAFER++ is the first rebound attack with standard differentials. To demonstrate the efficiency of proposed distinguishers, we provide formal proof of a lower bound for finding a differential pair that follows a truncated differential in the case of a random permutation. Our analysis shows that block ciphers used as the underlying primitive should also be analyzed in the open-key model to prevent possible collision attacks.

We analyze the IDEA-based hash functions in a variety of cipher modes. We present practical complexity collision search attacks and preimage attacks, where we exploit a null weak-key and a new non-trivial property of IDEA. We prove that even if a cipher is considered secure in the secret-key model, one has to be very careful when using it as a building block in the hashing modes.

Finally, we investigate the recent rotational analysis. We show how to extend the rotational analysis to subtractions, shifts, bit-wise Boolean functions, multi additions and multi subtractions. In particular, we develop formulae for calculation of probabilities of preserving the rotation property for multiple modular additions and subtra[...]




2015-02-22
13:11 [Event][New] SECITC'15: 8th International Conference on Security for Information Technology & Comm.

  Submission: 20 March 2015
Notification: 20 April 2015
From June 11 to June 7
Location: Bucharest, Romania
More Information: http://www.secitc.eu/


05:37 [Event][New] MSPN�2015: International Conference on Mobile, Secure and Programmable Networking

  Submission: 20 March 2015
Notification: 13 April 2015
From June 15 to June 17
Location: Paris, France
More Information: http://cedric.cnam.fr/workshops/mspn2015/


05:37 [Event][New] MSPN’2015: International Conference on Mobile, Secure and Programmable Networking

  Submission: 20 March 2015
Notification: 13 April 2015
From June 15 to June 17
Location: Paris, France
More Information: http://




2015-02-21
13:07 [Event][New] WISTP'2015: The 9th WISTP International Conference on Information Security Theory and P

  Submission: 10 April 2015
Notification: 30 May 2015
From August 24 to August 25
Location: Heraklion, Crete, Greece
More Information: http://www.wistp.org/




2015-02-20
08:08 [Event][New] Summer School on Fully Homomorphic Encryption and Multi-Linear Maps

  From October 12 to October 16
Location: Paris, France
More Information: http://www.heat-project.eu/summerschool2015.html




2015-02-16
07:17 [Pub][ePrint] On the security margin of MAC striping, by Thomas Eisenbarth and Aaron Meyerowitz and Rainer Steinwandt

  MAC striping has been suggested as a technique to authenticate encrypted payloads using short tags. For an idealized MAC scheme, the probability of a selective forgery has been estimated as $\\binom{\\ell+m}{m}^{-1}\\cdot 2^{-m}$, when utilizing MAC striping with $\\ell$-bit payloads and $m$-bit tags. We show that this estimate is too optimistic. For $m\\le\\ell$ and any payload, we achieve a selective forgery with probability $\\ge \\binom{\\ell+m}{m}^{-1}$, and usually many orders of magnitude more than that.



07:17 [Pub][ePrint] Structural Evaluation by Generalized Integral Property, by Yosuke Todo

  In this paper, we show structural cryptanalyses against two popular networks, i.e., the Feistel Network and the Substitute-Permutation Network (SPN). Our cryptanalyses are distinguishing attacks by an improved integral distinguisher. The integral distinguisher is one of the most powerful attacks against block ciphers, and it is usually constructed by evaluating the propagation characteristic of integral properties, e.g., the ALL or BALANCE property. However, the integral property does not derive useful distinguishers against block ciphers with non-bijective functions and bit-oriented structures. Moreover, since the integral property does not clearly exploit the algebraic degree of block ciphers, it tends not to construct useful distinguishers against block ciphers with low-degree functions. In this paper, we propose a new property called {\\it the division property}, which is the generalization of the integral property. It can effectively construct the integral distinguisher even if the block cipher has non-bijective functions, bit-oriented structures, and low-degree functions. From viewpoints of the attackable number of rounds or chosen plaintexts, the division property can construct better distinguishers than previous methods. Although our attack is a generic attack, it can improve several integral distinguishers against specific cryptographic primitives. For instance, it can reduce the required number of chosen plaintexts for the 10-round distinguisher on Keccak-f from $2^{1025}$ to $2^{515}$. For the Feistel cipher, it theoretically proves that Simon 32, 48, 64, 96, and 128 have 9-, 11-, 11-, 13-, and 13-round integral distinguishers, respectively.



07:17 [Pub][ePrint] Related-Key Forgeries for Prøst-OTR, by Christoph Dobraunig and Maria Eichlseder and Florian Mendel

  We present a forgery attack on Prøst-OTR in a related-key setting. Prøst is a family of authenticated encryption algorithms proposed as candidates in the currently ongoing CAESAR competition, and Prøst-OTR is one of the three variants of the Prøst design. The attack exploits how the Prøst permutation is used in an Even-Mansour construction in the Feistel-based OTR mode of operation. Given the ciphertext and tag for any two messages under two related keys K and K + Delta with related nonces, we can forge the ciphertext and tag for a modified message under K. If we can query ciphertexts for chosen messages under K + Delta, we can achieve almost universal forgery for K. The computational complexity is negligible.