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- Tomoyasu Suzaki, Kazuhiko Minematsu, Sumio Morioka, Eita Kobayashi
- Selected Areas in Cryptography
- 2012

This paper presents a 64-bit lightweight block cipher TWINE supporting 80 and 128bit keys. TWINE realizes quite small hardware implementation similar to the previous lightweight block cipher proposals, yet enables efficient software implementations on various platforms, from micro-controller to high-end CPU. This characteristic is obtained by the use of… (More)

- Kazuhiko Minematsu
- EUROCRYPT
- 2014

This paper proposes a new scheme for authenticated encryption (AE) which is typically realized as a blockcipher mode of operation. The proposed scheme has attractive features for fast and compact operation. When it is realized with a blockcipher, it requires one blockcipher call to process one input block (i.e. rate-1), and uses the encryption function of… (More)

- Tomoyasu Suzaki, Kazuhiko Minematsu
- FSE
- 2010

The generalized Feistel structure (GFS) is a generalized form of the classical Feistel cipher. A popular version of GFS, called TypeII, divides a message into k > 2 sub blocks and applies a (classical) Feistel transformation for every two sub blocks, and then performs a cyclic shift of k sub blocks. Type-II GFS has many desirable features for… (More)

- Kazuhiko Minematsu, Yukiyasu Tsunoo
- FSE
- 2006

We propose message authentication codes (MACs) that combine a block cipher and an additional (keyed or unkeyed) permutation. Our MACs are provably secure if the block cipher is pseudorandom and the additional permutation has a small differential probability. We also demonstrate that our MACs are easily implemented with AES and its 4-round version to obtain… (More)

- Tetsu Iwata, Keisuke Ohashi, Kazuhiko Minematsu
- CRYPTO
- 2012

In this paper, we study the security proofs of GCM (Galois/Counter Mode of Operation). We first point out that a lemma, which is related to the upper bound on the probability of a counter collision, is invalid. Both the original privacy and authenticity proofs by the designers are based on the lemma. We further show that the observation can be translated… (More)

We provide new security proofs for PMAC, TMAC, and XCBC message authentication modes. The previous security bounds for these modes were σ/2, where n is the block size in bits and σ is the total number of queried message blocks. Our new bounds are `q/2 for PMAC and `q/2 + `q/2 for TMAC and XCBC, where q is the number of queries and ` is the maximum message… (More)

- Kazuhiko Minematsu
- Selected Areas in Cryptography
- 2006

- Kazuhiko Minematsu
- FSE
- 2009

This paper studies how to build a 2n-bit block cipher which is hard to distinguish from a truly random permutation against attacks with q ≈ 2 queries, i.e., birthday attacks. Unlike previous approaches using pseudorandom functions, we present a simple and efficient proposal using a tweakable block cipher as an internal module. Our proposal is provably… (More)

- Kazuhiko Minematsu
- FSE
- 2010

The security of randomized message authentication code, MAC for short, is typically depending on the uniqueness of random initial vectors (IVs). Thus its security bound usually contains O(q/2), when random IV is n bits and q is the number of MACed messages. In this paper, we present how to break this birthday barrier without increasing the randomness. Our… (More)

- Tetsu Iwata, Kazuhiko Minematsu, Jian Guo, Sumio Morioka
- IACR Cryptology ePrint Archive
- 2014

We define and analyze the security of a blockcipher mode of operation, CLOC, for provably secure authenticated encryption with associated data. The design of CLOC aims at optimizing previous schemes, CCM, EAX, and EAX-prime, in terms of the implementation overhead beyond the blockcipher, the precomputation complexity, and the memory requirement. With these… (More)