High-Speed Block Cipher Algorithm Based on Hybrid Method Bac Do Thi1 and Minh Nguyen Hieu2 1
University of Information and Communication Technology, Thai Nguyen, Viet Nam
[email protected] 2 Le Qui Don Technical University, Ha Noi, Viet Nam
[email protected]
Abstract. This paper proposes 3 different designs of the new 64-bit block cipher diagram. A new feature of the designs is the application of hybrid CSPN (Controlled Substitution Permutation network). Designs with particular advantages will make the selection more appropriate for each target of applications. However, design shall meet all the security requirements to protect applications against the well-known threats. Keywords: hybrid CSPN, SDDO (Switchable Data Dependent Operation), Block cipher, key schedule.
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Introduction
Information security is one of the essential requirements of the communication system to ensure the system safety; one of solutions to the system security shall be applied with ciphers. However, the selection of appropriate ciphers with targets of different services is a significant factor for success of the service. Especially, such factor is required and evaluated carefully to apply to the high speed communication applications factors. Proposed several algorithms have been orientated the high-speed communications networks such as CIKS-1 [3], DDP-64 [3], Cobra-H64 [3], Cobra-S128 [4], etc. The previous studies was applied the homogeneous CSPN-based design, i.e., based on only one type CE (Controlled Element). However, creating hybrids CSPN from two type combined CE for use in cryptographic applications is a solution to be considered flexible and suitable for many different applications and support to promote the strong points of CEs in each specific design. This paper proposed a new block cipher called BM123-64. It was developed on the basis of different SDDOs, in which these operators are built from heterogeneous or hybrid CSPNs. This paper is structured as follows: section 2 presents the design model of heterogeneous and hybrid CSPNs; section 3 presents the new BM123-64 block cipher; section 4 presents the recommendations, forecasts and conclusions.
Y.-S. Jeong et al. (eds.), Ubiquitous Information Technologies and Applications, Lecture Notes in Electrical Engineering 280, DOI: 10.1007/978-3-642-41671-2_37, © Springer-Verlag Berlin Heidelberg 2014
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CSPN Design Used in Cryptographic
The general structure of CSPN was described in detail by Nikolay A. Moldovyan in [3] and is applied to construct the DDOs (Data Dependent Operation), SDDOs operators applied in many algorithms. Basically, both of CSPN types have the following common characteristics: only one CE in the diagram; multiple layers between which fixed permutations are interposed. According to [3], CSPN deems to be homogeneous. However, for the purpose of maintaining the generality of this design, a modification is proposed based on the combination of two separate CE called the hybrid CSPN model. Specifically, if the odd numbered layers have used one CE, the even numbered layers will be used with the other CE. An illustration of hybrid CSPN used in BM123-64 algorithm shall be shown below, F'16/64 hybrid operators (Fig. 1). Design of hybrid F'16/64 includes 4 layers, in which logical function of elements F2/2 selected from layer 1 and 3 shall be represented by the equation (1, 2, 3), while of element F'2/2 selected from 2, 4 layers shall be represented by equations (4, 5, 6) (see section 3). The permutation I1, I2 are described in Table 1.
Fig. 1. Hybrid structure of F’16/64, F’-116/64
Fig. 2. Structure of
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( , ) /
(a) and
( , ) /
(b)
Design of Algorithm BM123-64
BM123-64 block cipher will be proposed with size of 64-bit block, key length of 256 bits. It includes 8 transformable rounds which use Crypt(e) transformations as shown in Fig.3. The difference of the proposed algorithm from others is that, the algorithm is
High-Speed Block Cipher Algorithm Based on Hybrid Method
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built on the basis of CSPNs, SDDOs combined with the S4x4, S-14x4 boxes and fixed ( , ) permutations I, I1 (Table 1). In the propose algorithms, / SDDOs operators shall be applied. SDDOs are built on the basis of homogenous or hybrid CSPNs after embedding of SCO (Operator Controlled Switchable). The steps of BM123-64 are described as follows: 1. For j = 1 to 7 do: {(L, R) Crypt(e)(L, R, Uj, Qj ); (R, L) (L, R)}. 2. (L, R) Crypt(e)(L, R, U8 , Q8). 3. {(L, R) (L ⊕ U9, R ⊕ Q9); (L, R) (L, R)}.
Fig. 3. Structure round transformation Crypt(e) of BM123-64 Table 1. Description of fix permutations and E expanded operator in the algorithm I I1 I2 E
(1)(2,18)(3)(4,20)(5)(6,22)(7)(8,24)(9)(10,26)(11)(12,28)(13)(14,30)(15)(16,32)(17) (18,2)(19)(20,4)(21)(22,6)(23)(24,8)(25)(26,10)(27)(28,12)(29)(30,14)31)(32,16) (1)(2,5)(3,9)(4,13)(5,2)(6)(7,10)(8,14)(9,3)(10,7)(11)(12,15)(13,4)(14,8)(15,12) (16) (1)(2,3)(3,2)(4)(5)(6,7)(7,6)(8)(9)(10,11)(11,10)(12)(13)(14,15)(15,14) (16) E(X)=(X, X
