A New Class of Single Cycle T-Functions

Hong, Jin; Lee, Dong Hoon; Yeom, Yongjin; Han, Daewan

doi:10.1007/11502760_5

Cited by 22 publications

(29 citation statements)

References 21 publications

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“…TF-0m operates on a 256-bit state and the output sequence consists of the 32 most significant bits. Then, we cryptanalyse the TSC-family of stream ciphers [4], which operates on a 128-bit state and outputs 32 bits of the state using a filtering function. We find a very efficient distinguisher for TSC-1 with an expected 2 22 data complexity; for TSC-2, we describe a different distinguishing attack with an expected 2 34 data complexity.…”

Section: Contributions Of This Papermentioning

confidence: 99%

“…We start this section with a description of the recent proposal of stream cipher family TSC [4]. We find a very efficient distinguishing attack on TSC-1, as well as a distinguishing attack on TSC-2.…”

Section: Cryptanalysis Of Tscmentioning

confidence: 99%

“…Some of these proposals have been broken by Mitra and Sarkar [13] using time-memory tradeoffs. Based on the results of Klimov and Shamir, a new class of multi-word T-functions and two fully specified stream ciphers have been proposed by Hong et al [3,4]. Their schemes TSC-1 and TSC-2 have a transparent design and allow for some flexibility.…”

Section: Introductionmentioning

confidence: 99%

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Distinguishing Attacks on T-Functions

Künzli¹,

Junod

Meier³

2005

Progress in Cryptology – Mycrypt 2005

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Abstract. Klimov and Shamir proposed a new class of simple cryptographic primitives named T-functions. For two concrete proposals based on the squaring operation, a single word T-function and a previously unbroken multi-word T-function with a 256-bit state, we describe an efficient distinguishing attack having a 2 32 data complexity. Furthermore, Hong et al. recently proposed two fully specified stream ciphers, consisting of multi-word T-functions with 128-bit states and filtering functions. We describe distinguishing attacks having a 2 22 and a 2 34 data complexity, respectively. The attacks have been implemented.

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Section: Contributions Of This Papermentioning

confidence: 99%

Section: Cryptanalysis Of Tscmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Distinguishing Attacks on T-Functions

Künzli¹,

Junod

Meier³

2005

Progress in Cryptology – Mycrypt 2005

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“…More recently, Hong et al proposed a new class of single cycle T-functions, which have the property to use Sboxes [10]. They described two new algorithms.…”

Section: Introductionmentioning

confidence: 99%

Linear Cryptanalysis of the TSC Family of Stream Ciphers

Muller¹,

Peyrin²

2005

Lecture Notes in Computer Science

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Abstract. In this paper, we introduce a new cryptanalysis method for stream ciphers based on T-functions and apply it to the TSC family which was proposed by Hong et al.. Our attack are based on linear approximations of the algorithms (in particular of the T-function). Hence, it is related to correlation attack, a popular technique to break stream ciphers with a linear update, like those using LFSR's.We show a key-recovery attack for the two algorithms proposed at FSE 2005 : TSC-1 in 2 25.4 computation steps, and TSC-2 in 2 48.1 steps. The first attack has been implemented and takes about 4 minutes to recover the whole key on an average PC. Another algorithm in the family, called TSC-3, was proposed at the ECRYPT call for stream ciphers. Despite some differences with its predecessors, it can be broken by similar techniques. Our attack has complexity of 2 42 known keystream bits to distinguish it from random, and about 2 66 steps of computation to recover the full secret key.An extended version of this paper can be found on the ECRYPT website [23].

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“…At FSE 2005, Hong et al proposed a new class of single T-functions with S-box application [1], and described two stream ciphers TSC-1 and TSC-2. At Asiacrypt 2004, Mitra and Sarkar described a time-memory trade-off attack [8] to break some stream ciphers proposed by Klimov and Shamir.…”

Section: Introductionmentioning

confidence: 99%

Differential Cryptanalysis of T-Function Based Stream Cipher TSC-4

Zhang

Wang

2007

Lecture Notes in Computer Science

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Abstract. TSC-4 is a T-function based stream cipher with 80-bit key, and proposed as a candidate for ECRYPT eStream project. In this paper, we introduce a differential method to analyze TSC-4. Our attack is based on the vulnerable differential characteristics in the state initialization of TSC-4, and for the chosen IV pairs, the differential probability is up to 2 −15.40 in the case of weak keys. We show that there are about 2 72 weak keys among the total 2 80 keys. To recover 8 bits of a weak key needs about 2 40.53 chosen IV pairs. After that, we can search the other 72 key bits by an exhaustive attack.

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A New Class of Single Cycle T-Functions

Cited by 22 publications

References 21 publications

Distinguishing Attacks on T-Functions

Distinguishing Attacks on T-Functions

Linear Cryptanalysis of the TSC Family of Stream Ciphers

Differential Cryptanalysis of T-Function Based Stream Cipher TSC-4

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