Seongtaek Chee

HIGHT: a new block cipher suitable for low-resource device

In this paper, we propose a new block cipher HIGHT with 64-bit block length and 128-bit key length. It provides low-resource hardware implementation, which is proper to ubiquitous computing device such as a sensor in USN or a RFID tag. HIGHT does not only consist of simple operations to be ultra-light but also has enough security as a good encryption algorithm. Our hardware implementation of HIGHT requires 3048 gates on 0.25 μm technology.

New Block Cipher: ARIA

In this paper, we propose a 128-bit block cipher ARIA which is an involution substitution and permutation encryption network(SPN). We use the same S-boxes as Rijndael to eliminate defects which are caused by a totally involution structure. In the diffusion layer of ARIA, a 16× 16 binary matrix of the maximum branch number 8 is used to avoid some attacks well applied to the reduced round of Rijndael. ARIA uses only basic operations, S-box substitutions and XOR’s together with an involution structure so that it can be efficiently implemented on various platforms.

New Public Key Cryptosystem Using Finite Non Abelian Groups

Most public key cryptosystems have been constructed based on abelian groups up to now. We propose a new public key cryptosystem built on finite non abelian groups in this paper. It is convertible to a scheme in which the encryption and decryption are much faster than other well-known public key cryptosystems, even without no message expansion. Furthermore a signature scheme can be easily derived from it, while it is difficult to find a signature scheme using a non abelian group.

On the Correlation Immune Functions and Their Nonlinearity

In this paper, we consider the relationship between the nonlinearity and correlation immunity of functions suggested in [1], [3]. For the analysis of such functions, we present a simple method of generating the same set of functions, which makes us possible to construct correlation immune functions with controllable correlation immunity and nonlinearity.

Semi-bent Functions

Highly nonlinear balanced Boolean functions both satisfying the propagation criterion and having almost uniform correlation values with all linear functions are very important in the design of hash functions, stream and block ciphers. In particular, the output uncorrelated properties between two Boolean functions are required to design permutations. We present, so called, semi-bent functions which satisfy all of these properties.

On the Security of Rijndael-Like Structures against Differential and Linear Cryptanalysis

Rijndael-like structure is a special case of SPN structure. The linear transformation of Rijndael-like structures consists of linear transformations of two types, the one is byte permutation ? and the other is linear transformation ? = (?1, ?2, ?3, ?4), where each of ?i separately operates on each of the four columns of a state. Furthermore, ? and ? have some interestingprop erties. In this paper, we present a new method for upper boundingthe maximum differential probability and the maximum linear hull probability for Rijndael-like structures. By applyingour method to Rijndael, we obtain that the maximum differential probability and the maximum linear hull probability for 4 rounds of Rijndael are bounded by 1.06 × 2-96.

Global avalanche characteristics and propagation criterion of balanced Boolean functions

Abstract The GAC (Global Avalanche Characteristics) were introduced by Zhang and Zheng (1995) as a measure of cryptographic strength of Boolean functions. Two indicators σ ƒ and Δ ƒ related to GAC are introduced. Son et al. (1998) gave a lower bound on σ ƒ for a balanced Boolean function. In this paper, we provide an improved lower bound. Moreover, we provide bounds on nonlinearity for a balanced Boolean function satisfying the propagation criterion with respect to t vectors.

Global avalanche characteristics and nonlinearity of balanced Boolean functions

Abstract The GAC (global avalanche characteristic) was introduced to measure cryptographic behavior, such as, propagation characteristic, in a global manner. The two indicators σf and Δf related to GAC are introduced. However, an important problem to compute lower bounds of two indicators for balanced Boolean functions was not solved yet. In this paper, we derive lower bounds on the two indicators for balanced Boolean functions: σf ⩾ 22n + 2n + 3 and Δf ⩾ 8. Moreover, we obtain an upper bound on nonlinearity for balanced Boolean functions: N f ⩽ 2 n−1 − 1 2 2 − n 2 √σ f , which improves the previously known results.

Conditional Correlation Attack on Nonlinear Filter Generators

In this paper, the optimum correlation attack recently introduced by R. Anderson is improved to be applicable to most of the nonlinear filter generators. We propose a conditional correlation attack by introducing a novel notion of the conditional linear approximation. It is shown that there are always strong correlations between key stream sequences and their corresponding input bits or their linear combinations. Finally, we suggest a practical attacking method that can be applied to most of the nonlinear filter generators.

Elliptic Curves and Resilient Functions

In this paper, we propose a novel relationship between the correlation of two polynomial-type Boolean functions and the order of an associated algebraic curve. By this relationship, we propose a method to generate a resilient (correlation immune and balanced) function from a cubic polynomial. Since our resilient function is derived from a polynomial over a finite field, its nonlinearity is much easier to control. Moreover we can construct a resilient function with multi-bit outputs. We present several examples of a resilient function with 2 outputs.