Search

Your search keyword '"Sekar, Gautham"' showing total 40 results
Start Over Author "Sekar, Gautham"
40 results on '"Sekar, Gautham"'

2. Revisiting the Software-Efficient Stream Ciphers RCR-64 and RCR-32.

Author

Joseph, Mabin, Sekar, Gautham, and Balasubramanian, R

Abstract

The synchronous stream ciphers RCR-64 and RCR-32 designed by Sekar, Paul and Preneel are strengthened variants of the ciphers TPy and TPypy (designed by Biham and Seberry), respectively. The RCR ciphers have remained unbroken since they were published in 2007. In this paper, we present arguments that not only support the designers' security claims but suggest, in general, that the ciphers are secure against several classes of cryptanalytic attacks. We find that the ciphers are best used with 256-bit keys and 384-bit IVs. We also suggest ways to protect software implementations of the RCR ciphers against (cache-)timing and processor flag attacks. Our performance evaluation suggests that the protected implementation of the RCR-64 encrypts long messages at speeds comparable to some of the fastest stream ciphers available today. Consequently, we find that the RCR ciphers may be well suited for PC-based applications in general and streaming audio / video applications in particular. This is the first paper to present a detailed study on the security and performance of the RCR ciphers. [ABSTRACT FROM AUTHOR]

Published
2024
Full Text
View/download PDF

3. Distinguishing Attacks on (Ultra-)Lightweight WG Ciphers

Author

Joseph, Mabin, Sekar, Gautham, Balasubramanian, R., Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, and Bogdanov, Andrey, editor

Published
2017
Full Text
View/download PDF

5. Side Channel Cryptanalysis of Streebog

Author

Sekar, Gautham, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, Chen, Liqun, editor, and Matsuo, Shin'ichiro, editor

Published
2015
Full Text
View/download PDF

6. The Stream Cipher Core of the 3GPP Encryption Standard 128-EEA3: Timing Attacks and Countermeasures

Author

Sekar, Gautham, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Wu, Chuan-Kun, editor, Yung, Moti, editor, and Lin, Dongdai, editor

Published
2012
Full Text
View/download PDF

7. Practical Attacks on a Cryptosystem Proposed in Patent WO/2009/066313

Author

Sekar, Gautham, Preneel, Bart, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Jung, Souhwan, editor, and Yung, Moti, editor

Published
2012
Full Text
View/download PDF

8. Meet-in-the-Middle Attacks on Reduced-Round XTEA

Author

Sekar, Gautham, Mouha, Nicky, Velichkov, Vesselin, Preneel, Bart, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, and Kiayias, Aggelos, editor

Published
2011
Full Text
View/download PDF

9. Cryptanalysis of the ESSENCE Family of Hash Functions

Author

Mouha, Nicky, Sekar, Gautham, Aumasson, Jean-Philippe, Peyrin, Thomas, Thomsen, Søren S., Turan, Meltem Sönmez, Preneel, Bart, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Bao, Feng, editor, Yung, Moti, editor, Lin, Dongdai, editor, and Jing, Jiwu, editor

Published
2010
Full Text
View/download PDF

10. Improved Distinguishing Attacks on HC-256

Author

Sekar, Gautham, Preneel, Bart, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Takagi, Tsuyoshi, editor, and Mambo, Masahiro, editor

Published
2009
Full Text
View/download PDF

11. A New Approach to χ 2 Cryptanalysis of Block Ciphers

Author

Nakahara, Jorge, Jr., Sekar, Gautham, de Freitas, Daniel Santana, Chiann, Chang, de Souza, Ramon Hugo, Preneel, Bart, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Samarati, Pierangela, editor, Yung, Moti, editor, Martinelli, Fabio, editor, and Ardagna, Claudio A., editor

Published
2009
Full Text
View/download PDF

12. Correlated Keystreams in Moustique

Author

Käsper, Emilia, Rijmen, Vincent, Bjørstad, Tor E., Rechberger, Christian, Robshaw, Matt, Sekar, Gautham, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Vaudenay, Serge, editor

Published
2008
Full Text
View/download PDF

13. New Attacks on the Stream Cipher TPy6 and Design of New Ciphers the TPy6-A and the TPy6-B

Author

Sekar, Gautham, Paul, Souradyuti, Preneel, Bart, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Lucks, Stefan, editor, Sadeghi, Ahmad-Reza, editor, and Wolf, Christopher, editor

Published
2008
Full Text
View/download PDF

14. Improved Meet-in-the-Middle Attacks on Reduced-Round DES

Author

Dunkelman, Orr, Sekar, Gautham, Preneel, Bart, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Srinathan, K., editor, Rangan, C. Pandu, editor, and Yung, Moti, editor

Published
2007
Full Text
View/download PDF

15. Related-Key Attacks on the Py-Family of Ciphers and an Approach to Repair the Weaknesses

Author

Sekar, Gautham, Paul, Souradyuti, Preneel, Bart, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Srinathan, K., editor, Rangan, C. Pandu, editor, and Yung, Moti, editor

Published
2007
Full Text
View/download PDF

16. New Weaknesses in the Keystream Generation Algorithms of the Stream Ciphers TPy and Py

Author

Sekar, Gautham, Paul, Souradyuti, Preneel, Bart, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Garay, Juan A., editor, Lenstra, Arjen K., editor, Mambo, Masahiro, editor, and Peralta, René, editor

Published
2007
Full Text
View/download PDF

17. Distinguishing Attacks on the Stream Cipher Py

Author

Paul, Souradyuti, Preneel, Bart, Sekar, Gautham, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Robshaw, Matthew, editor

Published
2006
Full Text
View/download PDF

18. Challenging the increased resistance of regular hash functions against birthday attacks

Author

Mouha Nicky, Sekar Gautham, and Preneel Bart

Subjects
hash function, balance, regularity, birthday attack, (linear) subset regularity, random function, Mathematics, QA1-939
Abstract

At Eurocrypt 2004, Bellare and Kohno presented the concept of a regular hash function. For a hash function to be regular, every hash value must have the same number of preimages in the domain. The findings of their paper remained unchallenged for over six years, and made their way into several research papers and textbooks. In their paper, Bellare and Kohno claim that regular hash functions are more resistant against the birthday attack than random hash functions. We counter their arguments, by showing that the success probability of the birthday attack against a regular hash function can be made arbitrarily close to that of a random hash function (for the same number of trials). Our analysis uses the fact that the choices of the attacker can be limited to any subset of the domain. Furthermore, we prove that it is not possible to construct a hash function that is regular for only a small fraction of subsets of the domain. In order to avoid these problems, we propose to model hash functions as random functions. Compared to regular functions, we argue that the statistics of random functions are more similar to hash functions used in practice, regardless of how the attacker chooses the domain points.

Published
2012
Full Text
View/download PDF

19. On the Security of the Stream Ciphers RCR-64 and RCR-32.

Author

Joseph, Mabin, Sekar, Gautham, Balasubramanian, R, and Venkiteswaran, G

Subjects
*STREAM ciphers, *BLOCK ciphers, *CIPHERS, *COMPUTER science, *PERIODICAL publishing
Abstract

The stream ciphers RCR-64 and RCR-32 designed by Sekar et al. are the most recent additions to the Py-family of stream ciphers, originally designed by Biham et al. The ciphers are among the fastest stream ciphers on software. To the best of our knowledge, the only reported attacks on the ciphers are due to Ding et al. , published in the Journal of Universal Computer Science. In this paper, we review these alleged attacks on the RCR ciphers and show that they are based on non-existent keystream biases stemming from flawed probability calculations. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

35. Practical (Second) Preimage Attacks on the TCS_SHA-3 Family of Cryptographic Hash Functions.

Author

Sekar, Gautham and Bhattacharya, Soumyadeep

Abstract

TCS_SHA-3 is a family of four cryptographic hash functions that are covered by a United States patent (US 2009/0262925). The digest sizes are 224, 256, 384 and 512 bits. The hash functions use bijective functions in place of the standard compression functions. In this paper we describe first and second preimage attacks on the full hash functions. The second preimage attack requires negligible time and the first preimage attack requires O(236) time. In addition to these attacks, we also present a negligible time second preimage attack on a strengthened variant of the TCS_SHA-3. All the attacks have negligible memory requirements. To the best of our knowledge, there is no prior cryptanalysis of any member of the TCS_SHA-3 family in the literature. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

36. Cryptanalysis of the ESSENCE Family of Hash Functions.

Author

Mouha, Nicky, Sekar, Gautham, Aumasson, Jean-Philippe, Peyrin, Thomas, Thomsen, Søren S., Turan, Meltem Sönmez, and Preneel, Bart

Abstract

ESSENCE is a family of cryptographic hash functions, accepted to the first round of NIST΄s SHA-3 competition. This paper presents the first known attacks on ESSENCE. We present a semi-free-start collision attack on 31 out of 32 rounds of ESSENCE-512, invalidating the design claim that at least 24 rounds of ESSENCE are secure against differential cryptanalysis. We develop a novel technique to satisfy the first nine rounds of the differential characteristic. Non-randomness in the outputs of the feedback function F is used to construct several distinguishers on a 14-round ESSENCE block cipher and the corresponding compression function, each requiring only 217 output bits. This observation is extended to key-recovery attacks on the block cipher. Next, we show that the omission of round constants allows slid pairs and fixed points to be found. These attacks are independent of the number of rounds. Finally, we suggest several countermeasures against these attacks, while still keeping the design simple and easy to analyze. [ABSTRACT FROM AUTHOR]

Published
2011
Full Text
View/download PDF

37. Related-Key Attacks on the Py-Family of Ciphers and an Approach to Repair the Weaknesses.

Author

Hutchison, David, Kanade, Takeo, Kittler, Josef, Kleinberg, Jon M., Mattern, Friedemann, Mitchell, John C., Naor, Moni, Nierstrasz, Oscar, Pandu Rangan, C., Steffen, Bernhard, Sudan, Madhu, Terzopoulos, Demetri, Tygar, Doug, Vardi, Moshe Y., Weikum, Gerhard, Srinathan, K., Rangan, C. Pandu, Yung, Moti, Sekar, Gautham, and Paul, Souradyuti

Abstract

The stream cipher TPypy has been designed by Biham and Seberry in January 2007 as the strongest member of the Py-family ciphers, after weaknesses in the other members Py, Pypy, Py6 were discovered. One main contribution of the paper is the detection of related-key weaknesses in the Py-family of ciphers including the strongest member TPypy. Under related keys, we show a distinguishing attack on TPypy with data complexity 2192.3 which is lower than the previous best known attack on the cipher by a factor of 288. It is shown that the above attack also works on the other members TPy, Pypy and Py. A second contribution of the paper is design and analysis of two fast ciphers RCR-64 and RCR-32 which are derived from the TPy and the TPypy respectively. The performances of the RCR-64 and the RCR-32 are 2.7 cycles/byte and 4.45 cycles/byte on Pentium III (note that the speeds of the ciphers Py, Pypy and RC4 are 2.8, 4.58 and 7.3 cycles/byte). Based on our security analysis, we conjecture that no attacks lower than brute force are possible on the RCR ciphers. [ABSTRACT FROM AUTHOR]

Published
2007
Full Text
View/download PDF

38. Improved Meet-in-the-Middle Attacks on Reduced-Round DES.

Author

Hutchison, David, Kanade, Takeo, Kittler, Josef, Kleinberg, Jon M., Mattern, Friedemann, Mitchell, John C., Naor, Moni, Nierstrasz, Oscar, Pandu Rangan, C., Steffen, Bernhard, Sudan, Madhu, Terzopoulos, Demetri, Tygar, Doug, Vardi, Moshe Y., Weikum, Gerhard, Srinathan, K., Rangan, C. Pandu, Yung, Moti, Dunkelman, Orr, and Sekar, Gautham

Abstract

The Data Encryption Standard (DES) is a 64-bit block cipher. Despite its short key size of 56 bits, DES continues to be used to protect financial transactions valued at billions of Euros. In this paper, we investigate the strength of DES against attacks that use a limited number of plaintexts and ciphertexts. By mounting meet-in-the-middle attacks on reduced-round DES, we find that up to 6-round DES is susceptible to this kind of attacks. The results of this paper lead to a better understanding on the way DES can be used. [ABSTRACT FROM AUTHOR]

Published
2007
Full Text
View/download PDF

39. New Weaknesses in the Keystream Generation Algorithms of the Stream Ciphers TPy and Py.

Author

Hutchison, David, Kanade, Takeo, Kittler, Josef, Kleinberg, Jon M., Mattern, Friedemann, Mitchell, John C., Naor, Moni, Nierstrasz, Oscar, Pandu Rangan, C., Steffen, Bernhard, Sudan, Madhu, Terzopoulos, Demetri, Tygar, Doug, Vardi, Moshe Y., Weikum, Gerhard, Garay, Juan A., Lenstra, Arjen K., Mambo, Masahiro, Peralta, René, and Sekar, Gautham

Abstract

The stream ciphers Py, Py6 designed by Biham and Seberry were promising candidates in the ECRYPT-eSTREAM project because of their impressive speed. Since their publication in April 2005, a number of cryptanalytic weaknesses of the ciphers have been discovered. As a result, a strengthened version Pypy was developed to repair these weaknesses; it was included in the category of ‘Focus ciphers' of the Phase II of the eSTREAM competition. However, even the new cipher Pypy was not free from flaws, resulting in a second redesign. This led to the generation of three new ciphers TPypy, TPy and TPy6. The designers claimed that TPy would be secure with a key size up to 256 bytes, i.e., 2048 bits. In February 2007, Sekar et al. published an attack on TPy with 2281 data and comparable time. This paper shows how to build a distinguisher with 2275 key/IVs and one outputword per each key (i.e., the distinguisher can be constructed within the design specifications); it uses a different set of weak states of the TPy. Our results show that distinguishing attacks with complexity lower than the brute force exist if the key size of TPy is longer than 275 bits. Furthermore, we discover a large number of similar bias-producing states of TPy and provide a general framework to compute them. The attacks on TPy are also shown to be effective on Py. [ABSTRACT FROM AUTHOR]

Published
2007
Full Text
View/download PDF

40. Distinguishing Attacks on the Stream Cipher Py.

Author

Robshaw, Matthew, Paul, Souradyuti, Preneel, Bart, and Sekar, Gautham

Abstract

The stream cipher Py designed by Biham and Seberry is a submission to the ECRYPT stream cipher competition. The cipher is based on two large arrays (one is 256 bytes and the other is 1040 bytes) and it is designed for high speed software applications (Py is more than 2.5 times faster than the RC4 on Pentium III). The paper shows a statistical bias in the distribution of its output-words at the 1st and 3rd rounds. Exploiting this weakness, a distinguisher with advantage greater than 50% is constructed that requires 284.7 randomly chosen key/IV's and the first 24 output bytes for each key. The running time and the data required by the distinguisher are t284.7 and 289.2 respectively (t denotes the running time of the key/IV setup). We further show that the data requirement can be reduced by a factor of about 3 with a distinguisher that considers outputs of later rounds. In such case the running time is reduced to t284.7 (t denotes the time for a single round of Py). The Py specification allows a 256-bit key and a keystream of 264 bytes per key/IV. As an ideally secure stream cipher with the above specifications should be able to resist the attacks described before, our results constitute an academic break of Py. In addition we have identified several biases among pairs of bits; it seems possible to combine all the biases to build more efficient distinguishers. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results