Achievement Award
Development of Fast Encryption Algorithm KCipher-2 and its Standardization
Toshiaki TANAKA，Shinsaku KIYOMOTO，Kouichi SAKURAI

Toshiaki TANAKA
Shinsaku KIYOMOTO
Kouichi SAKURAI		      
  Encryption algorithms are widely used in the modern world of ICT. The award winners were engaged in a design project to develop an encryption algorithm that achieves rapid encryption that is 10-fold faster than the existing standard cipher, AES, and they proposed a new stream cipher named KCipher-2 [1], shown in Figure 1.


Figure 1: KCipher-2
The ambitious project goal aimed at achieving performance that would still be competitive ten years from now, and is applicable to resource constrained devices such as IoT devices. KCipher-2 includes a novel component called the dynamic feedback shift register (DFSR), which is designed to improve performance in software implementation and is secure against several kinds of attacks. KCipher-2 is 5-10 times faster than AES implementations [2] as shown in Figure 2, and the algorithm consists of basic operations such as exclusive-or, addition, and table look-up. 　


Figure 2: Performance of AES and KCipher-2
Therefore, it can operate on several platforms and achieves high throughputs for encryption and decryption. The Cryptographic Research and Evaluation Committee (CRYPTREC) has evaluated the security of KCipher-2 and concluded the cipher has a sufficient security margin to withstand all possible attacks.
  The award winners were also engaged in standardization work for KCipher-2 in ISO/IEC JTC1 SC27 WG2. KCipher-2 has been approved by the committee and published as ISO/IEC 18033-4 [3], which is the global standard for stream cipher algorithms. KCipher-2 is included in the e-Government Recommended Ciphers List in Japan [4], and IETF RFC7008, which describes the KCipher-2 algorithm, has been published as well. KCipher-2 has been widely used in commercial services: e.g. security modules for smart phones (more than 10 million terminals), a governmental system using mobile phones (34,000 terminals), and customer point services.
  In summary, the project KCipher-2 undertaken by the award winners has resulted in the successful launch of an outstanding cipher algorithm incorporated into ICT commercial products, contributes to standardisation in ISO/IEC, and provides a new recommended cipher for Japanese governmental systems. Their work has been widely acclaimed and received such awards as the Frontier Technology Award from the Ministry of Economy, Trade, and Industry, and the Science and Technology Award from the Ministry of Education, Culture, Sports, Science, and Technology.
  Therefore, the achievements of the award winners are outstanding and worthy of receiving the IEICE Achievement Award.
References
  1. （1）S. Kiyomoto, T. Tanaka, K. Sakurai, “K2 Stream Cipher,” ICETE 2007(Selected Paper), CCIS, Vol.23, pp.214-226, Springer, 2008.
  2. （2） Y. Nakano, K. Fukushima, S. Kiyomoto, T. Ishiguro, Y. Miyake, T. Tanaka, K. Sakurai, “Fast Implementation of KCipher-2 for Software and Hardware,” IEICE Trans. on Information and Systems, Vol.E97-D, No.1, pp.43-52, 2014.
  3. （3） ISO/IEC 18033-4:2011, Information technology -- Security techniques -- Encryption algorithms -- Part 4: Stream ciphers.
  4. （4）CRYPTREC, the e-Government Recommended Ciphers List in Japan, March 2013.
  5. （5）IETF RFC7008, A Description of the KCipher-2 Encryption Algorithm, August 2013.
 

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