Cryptanalysis of MORUS. / Ashur, Tomer; Eichlseder, Maria; Lauridsen, Martin; Leurent, Gaetan; Minaud, Brice; Rotella, Yann; Sasaki, Yu; Viguier, Benoit.

2018. 35-64 Paper presented at 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, Australia.

Research output: Contribution to conferencePaper

E-pub ahead of print

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Cryptanalysis of MORUS. / Ashur, Tomer; Eichlseder, Maria; Lauridsen, Martin; Leurent, Gaetan; Minaud, Brice; Rotella, Yann; Sasaki, Yu; Viguier, Benoit.

2018. 35-64 Paper presented at 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, Australia.

Research output: Contribution to conferencePaper

Harvard

Ashur, T, Eichlseder, M, Lauridsen, M, Leurent, G, Minaud, B, Rotella, Y, Sasaki, Y & Viguier, B 2018, 'Cryptanalysis of MORUS' Paper presented at 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, Australia, 2/12/18 - 6/12/18, pp. 35-64. https://doi.org/10.1007/978-3-030-03329-3_2

APA

Ashur, T., Eichlseder, M., Lauridsen, M., Leurent, G., Minaud, B., Rotella, Y., ... Viguier, B. (2018). Cryptanalysis of MORUS. 35-64. Paper presented at 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, Australia. https://doi.org/10.1007/978-3-030-03329-3_2

Vancouver

Ashur T, Eichlseder M, Lauridsen M, Leurent G, Minaud B, Rotella Y et al. Cryptanalysis of MORUS. 2018. Paper presented at 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, Australia. https://doi.org/10.1007/978-3-030-03329-3_2

Author

Ashur, Tomer ; Eichlseder, Maria ; Lauridsen, Martin ; Leurent, Gaetan ; Minaud, Brice ; Rotella, Yann ; Sasaki, Yu ; Viguier, Benoit. / Cryptanalysis of MORUS. Paper presented at 24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Brisbane, Australia.30 p.

BibTeX

@conference{6e92e9e627904198bedd2a625fa7b1f0,
title = "Cryptanalysis of MORUS",
abstract = "MORUS is a high-performance authenticated encryption algorithm submitted to the CAESAR competition, and recently selected as a finalist. There are three versions of MORUS: MORUS-640 with a 128-bit key, and MORUS-1208 with 128-bit or 256-bit keys. For all versions the security claim for confidentiality matches the key size. In this paper, we analyze the components of this algorithm (initialization, state update and tag generation), and report several results.As our main result, we present a linear correlation in the keystream of full MORUS, which can be used to distinguish its output from random and to recover some plaintext bits in the broadcast setting. For MORUS-1208, the correlation is $2^{-76}$, which can be exploited after around $2^{152}$ encryptions, less than would be expected for a 256-bit secure cipher. For MORUS-640, the same attack results in a correlation of $2^{-73}$, which does not violate the security claims of the cipher.To identify this correlation, we make use of rotational symmetries in MORUS using linear masks that are invariant by word-rotations of the state. This motivates us to introduce single-word versions of MORUS called MiniMORUS, which simplifies the analysis. The attack has been implemented and verified on MiniMORUS, where it yields a correlation of $2^{-16}$.We also study reduced versions of the initialization and finalization of MORUS, aiming to evaluate the security margin of these components. We show a forgery attack when finalization is reduced from 10 steps to 3, and a key-recovery attack in the nonce-misuse setting when initialization is reduced from 16 steps to 10. These additional results do not threaten the full MORUS, but studying all aspects of the design is useful to understand its strengths and weaknesses.",
keywords = "MORUS, CAESAR, authenticated encryption, Cryptanalysis",
author = "Tomer Ashur and Maria Eichlseder and Martin Lauridsen and Gaetan Leurent and Brice Minaud and Yann Rotella and Yu Sasaki and Benoit Viguier",
year = "2018",
month = "10",
day = "27",
doi = "10.1007/978-3-030-03329-3_2",
language = "English",
pages = "35--64",
note = "24th Annual International Conference on the Theory and Application of Cryptology and Information Security, Asiacrypt 2018 ; Conference date: 02-12-2018 Through 06-12-2018",
url = "https://asiacrypt.iacr.org/2018/",

}

RIS

TY - CONF

T1 - Cryptanalysis of MORUS

AU - Ashur, Tomer

AU - Eichlseder, Maria

AU - Lauridsen, Martin

AU - Leurent, Gaetan

AU - Minaud, Brice

AU - Rotella, Yann

AU - Sasaki, Yu

AU - Viguier, Benoit

PY - 2018/10/27

Y1 - 2018/10/27

N2 - MORUS is a high-performance authenticated encryption algorithm submitted to the CAESAR competition, and recently selected as a finalist. There are three versions of MORUS: MORUS-640 with a 128-bit key, and MORUS-1208 with 128-bit or 256-bit keys. For all versions the security claim for confidentiality matches the key size. In this paper, we analyze the components of this algorithm (initialization, state update and tag generation), and report several results.As our main result, we present a linear correlation in the keystream of full MORUS, which can be used to distinguish its output from random and to recover some plaintext bits in the broadcast setting. For MORUS-1208, the correlation is $2^{-76}$, which can be exploited after around $2^{152}$ encryptions, less than would be expected for a 256-bit secure cipher. For MORUS-640, the same attack results in a correlation of $2^{-73}$, which does not violate the security claims of the cipher.To identify this correlation, we make use of rotational symmetries in MORUS using linear masks that are invariant by word-rotations of the state. This motivates us to introduce single-word versions of MORUS called MiniMORUS, which simplifies the analysis. The attack has been implemented and verified on MiniMORUS, where it yields a correlation of $2^{-16}$.We also study reduced versions of the initialization and finalization of MORUS, aiming to evaluate the security margin of these components. We show a forgery attack when finalization is reduced from 10 steps to 3, and a key-recovery attack in the nonce-misuse setting when initialization is reduced from 16 steps to 10. These additional results do not threaten the full MORUS, but studying all aspects of the design is useful to understand its strengths and weaknesses.

AB - MORUS is a high-performance authenticated encryption algorithm submitted to the CAESAR competition, and recently selected as a finalist. There are three versions of MORUS: MORUS-640 with a 128-bit key, and MORUS-1208 with 128-bit or 256-bit keys. For all versions the security claim for confidentiality matches the key size. In this paper, we analyze the components of this algorithm (initialization, state update and tag generation), and report several results.As our main result, we present a linear correlation in the keystream of full MORUS, which can be used to distinguish its output from random and to recover some plaintext bits in the broadcast setting. For MORUS-1208, the correlation is $2^{-76}$, which can be exploited after around $2^{152}$ encryptions, less than would be expected for a 256-bit secure cipher. For MORUS-640, the same attack results in a correlation of $2^{-73}$, which does not violate the security claims of the cipher.To identify this correlation, we make use of rotational symmetries in MORUS using linear masks that are invariant by word-rotations of the state. This motivates us to introduce single-word versions of MORUS called MiniMORUS, which simplifies the analysis. The attack has been implemented and verified on MiniMORUS, where it yields a correlation of $2^{-16}$.We also study reduced versions of the initialization and finalization of MORUS, aiming to evaluate the security margin of these components. We show a forgery attack when finalization is reduced from 10 steps to 3, and a key-recovery attack in the nonce-misuse setting when initialization is reduced from 16 steps to 10. These additional results do not threaten the full MORUS, but studying all aspects of the design is useful to understand its strengths and weaknesses.

KW - MORUS

KW - CAESAR

KW - authenticated encryption

KW - Cryptanalysis

U2 - 10.1007/978-3-030-03329-3_2

DO - 10.1007/978-3-030-03329-3_2

M3 - Paper

SP - 35

EP - 64

ER -