KASUMI (block cipher)
| General | |
|---|---|
| Designers | Mitsubishi Electric |
| Derived from | MISTY1 |
| Cipher detail | |
| Key sizes | 128 bits |
| Block sizes | 64 bits |
| Structure | Feistel network |
| Rounds | 8 |
KASUMI is a block cipher used in UMTS, GSM, and GPRS mobile communications systems. In UMTS, KASUMI is used in the confidentiality (f8) and integrity algorithms (f9) with names UEA1 and UIA1, respectively. In GSM, KASUMI is used in the A5/3 key stream generator and in GPRS in the GEA3 key stream generator.
KASUMI was designed for 3GPP to be used in UMTS security system by the Security Algorithms Group of Experts (SAGE), a part of the European standards body ETSI. Because of schedule pressures in 3GPP standardization, instead of developing a new cipher, SAGE agreed with 3GPP technical specification group (TSG) for system aspects of 3G security (SA3) to base the development on an existing algorithm that had already undergone some evaluation. They chose the cipher algorithm MISTY1 developed and patented by Mitsubishi Electric Corporation. The original algorithm was slightly modified for easier hardware implementation and to meet other requirements set for 3G mobile communications security.
KASUMI is named after the original algorithm MISTY1 — (hiragana , romaji ) is the Japanese word for "mist".
In January 2010, Orr Dunkelman, Nathan Keller and Adi Shamir released a paper showing that they could break Kasumi with a related key attack and very modest computational resources; this attack is ineffective against MISTY1.
KASUMI algorithm is specified in a 3GPP technical specification. KASUMI is a block cipher with 128-bit key and 64-bit input and output. The core of KASUMI is an eight-round Feistel network. The round functions in the main Feistel network are irreversible Feistel-like network transformations. In each round the round function uses a round key which consists of eight 16-bit sub keys derived from the original 128-bit key using a fixed key schedule.
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