Journal of Korea Society of Industrial Information Systems (한국산업정보학회논문지)

Korea Society of Industrial Information Systems (한국산업정보학회)
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Modified AES having same structure in encryption and decryption

암호와 복호가 동일한 변형 AES

  • 조경연 (부경대학교 공과대학 IT융합응용공학과) ;
  • 송홍복 (동의대학교 공과대학 전자공학과)
  • Received : 2010.01.27
  • Accepted : 2010.06.08
  • Published : 2010.06.30
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Abstract

Feistel and SPN are the two main structures in a block cipher. Feistel is a symmetric structure which has the same structure in encryption and decryption, but SPN is not a symmetric structure. In this paper, we propose a SPN which has a symmetric structure in encryption and decryption. The whole operations of proposed algorithm are composed of the even numbers of N rounds where the first half of them, 1 to N/2 round, applies a right function and the last half of them, (N+1)/2 to N round, employs an inverse function. And a symmetry layer is located in between the right function layer and the inverse function layer. In this paper, AES encryption and decryption function are selected for the right function and the inverse function, respectively. The symmetric layer is composed with simple matrix and round key addition. Due to the simplicity of the symmetric SPN structure in hardware implementation, the proposed modified AES is believed to construct a safe and efficient cipher in Smart Card and RFID environments where electronic chips are built in.

블록 암호는 Feistel 구조와 SPN 구조로 나눌 수 있다. Feistel 구조는 암호 및 복호 알고리즘이 같은 구조이고, SPN 구조는 암호 및 복호 알고리즘이 다르다. 본 논문에서는 암호와 복호 과정이 동일한 SPN 구조 블록 암호 알고리즘을 제안한다. 즉 SPN 구조 전체를 짝수인 N 라운드로 구성하고 1 라운드부터 N/2 라운드까지는 정함수를 적용하고, (N/2)+1 라운드부터 N 라운드까지는 역함수를 적용한다. 또한 정함수단과 역함수단 사이에 대칭 블록을 구성하는 대칭단을 삽입한다. 본 논문에서 정함수로는 AES의 암호 알고리즘을, 역함수로는 AES의 복호 알고리즘을 사용하고, 대칭단은 간단한 행렬식과 라운드 키 합산으로 구성한다. 본 논문에서 제안한 암호와 복호가 동일한 변형 AES는 하드웨어 구성이 간단한 장점을 가지므로 제한적 하드웨어 및 소프트웨어 환경인 스마트카드와 전자 칩이 내장된 태그와 같은 RFID 환경에서 안전하고 효율적인 암호 시스템을 구성할 수 있다.

Keywords

References

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