International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Jongsung Kim

Affiliation: Center for Information Security Technologies(CIST)

Publications

Year
Venue
Title
2010
EPRINT
Related-Key Boomerang and Rectangle Attacks
This paper introduces the related-key boomerang and the related-key rectangle attacks. These new attacks can expand the cryptanalytic toolbox, and can be applied to many block ciphers. The main advantage of these new attacks, is the ability to exploit the related-key model twice. Hence, even ciphers which were considered resistant to either boomerang or related-key differential attacks may be broken using the new techniques. In this paper we present a rigorous treatment of the related-key boomerang and the related-key rectangle distinguishers. Following this treatment, we devise optimal distinguishing algorithms using the LLR (Logarithmic Likelihood Ratio) statistics. We then analyze the success probability under reasonable independence assumptions, and verify the computation experimentally by implementing an actual attack on a 6-round variant of KASUMI. The paper ends with a demonstration of the strength of our new proposed techniques with attacks on 10-round AES-192 and the full KASUMI.
2008
FSE
2008
EPRINT
Linear and Differential Cryptanalysis of Reduced SMS4 Block Cipher
SMS4 is a 128-bit block cipher with a 128-bit user key and 32 rounds, which is used in WAPI, the Chinese WLAN national standard. In this paper, we present a linear attack and a differential attack on a 22-round reduced SMS4; our 22-round linear attack has a data complexity of 2^{117} known plaintexts, a memory complexity of 2^{109} bytes and a time complexity of 2^{109.86} 22-round SMS4 encryptions and 2^{120.39} arithmetic operations, while our 22-round differential attack requires 2^{118} chosen plaintexts, 2^{123} memory bytes and 2^{125.71} 22-round SMS4 encryptions. Both of our attacks are better than any previously known cryptanalytic results on SMS4 in terms of the number of attacked rounds. Furthermore, we present a boomerang and a rectangle attacks on a 18-round reduced SMS4. These results are better than previously known rectangle attacks on reduced SMS4. The methods presented to attack SMS4 can be applied to other unbalanced Feistel ciphers with incomplete diffusion.
2008
EPRINT
New Impossible Differential Attacks on AES
In this paper we apply impossible differential attacks to reduced round AES. Using various techniques, including the early abort approach and key schedule considerations, we significantly improve previously known attacks due to Bahrak-Aref and Phan. The improvement of these attacks leads to the best known impossible differential attacks on 7-round AES-128 and AES-192, as well as to the best known impossible differential attacks on 8-round AES-256.
2007
FSE
2006
CHES
2006
EPRINT
On the Security of HMAC and NMAC Based on HAVAL, MD4, MD5, SHA-0 and SHA-1
HMAC is a widely used message authentication code and a pseudorandom function generator based on cryptographic hash functions such as MD5 and SHA-1. It has been standardized by ANSI, IETF, ISO and NIST. HMAC is proved to be secure as long as the compression function of the underlying hash function is a pseudorandom function. In this paper we devise two new distinguishers of the structure of HMAC, called {\em differential} and {\em rectangle distinguishers}, and use them to discuss the security of HMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1. We show how to distinguish HMAC with reduced or full versions of these cryptographic hash functions from a random function or from HMAC with a random function. We also show how to use our differential distinguisher to devise a forgery attack on HMAC. Our distinguishing and forgery attacks can also be mounted on NMAC based on HAVAL, MD4, MD5, SHA-0 and SHA-1. Furthermore, we show that our differential and rectangle distinguishers can lead to second-preimage attacks on HMAC and NMAC.
2006
EPRINT
Combined Differential, Linear and Related-Key Attacks on Block Ciphers and MAC Algorithms
Jongsung Kim
Differential and linear attacks are the most widely used cryptanalytic tools to evaluate the security of symmetric-key cryptography. Since the introduction of differential and linear attacks in the early 1990's, various variants of these attacks have been proposed such as the truncated differential attack, the impossible differential attack, the square attack, the boomerang attack, the rectangle attack, the differential-linear attack, the multiple linear attack, the nonlinear attack and the bilinear attack. One of the other widely used cryptanalytic tools is the related-key attack. Unlike the differential and linear attacks, this attack is based on the assumption that the cryptanalyst can obtain plaintext and ciphertext pairs by using different, but related keys. This thesis provides several new combined differential, linear and related-key attacks, and shows their applications to block ciphers, hash functions in encryption mode and message authentication code (MAC) algorithms. The first part of this thesis introduces how to combine the differential-style, linear-style and related-key attacks: we combine them to devise the differential-nonlinear attack, the square-(non)linear attack, the related-key differential-(non)linear attack, the related-key boomerang attack and the related-key rectangle attack. The second part of this thesis presents some applications of the combined attacks to exiting symmetric-key cryptography. Firstly, we present their applications to the block ciphers SHACAL-1, SHACAL-2 and AES. In particular, we show that the differential-nonlinear attack is applicable to 32-round SHACAL-2, which leads to the best known attack on SHACAL-2 that uses a single key. We also show that the related-key rectangle attack is applicable to the full SHACAL-1, 42-round SHACAL-2 and 10-round AES-192, which lead to the first known attack on the full SHACAL-1 and the best known attacks on SHACAL-2 and AES-192 that use related keys. Secondly, we exploit the related-key boomerang attack to present practical distinguishing attacks on the cryptographic hash functions MD4, MD5 and HAVAL in encryption mode. Thirdly, we show that the related-key rectangle attack can be used to distinguish instantiated HMAC and NMAC from HMAC and NMAC with a random function.
2005
FSE
2005
EPRINT
On the Security of Encryption Modes of MD4, MD5 and HAVAL
MD4 is a cryptographic hash function introduced in 1990 by Rivest. After MD4 was proposed, several hash functions such as MD5, HAVAL, RIPEMD, RIPEMD-160, SHA-1 and SHA-256 were designed based on the MD4 structure. In this paper, we cryptanalyze the compression functions of MD4, MD5 and 4-, 5-pass HAVAL in encryption modes. We exploit the recently proposed related-key rectangle and boomerang techniques to show non-randomness of MD4, MD5 and 4-, 5-pass HAVAL and to distinguish them from a randomly chosen cipher. The attacks are highly practical and have been confirmed by our experiments.
2002
ASIACRYPT

Program Committees

Asiacrypt 2011