KASUMI

In cryptography, KASUMI, also called A5/3, is a block cipher unit used in confidentiality algorithms (f8) and integrity (f9) for 3GPP mobile telephony. KASUMI was designed by the SAGE group (Security Algorithms Group of Experts in English), which is part of the European standards body ETSI. Rather than invent a zero-bottom cipher, SAGE selected an existing algorithm called MISTY1. For its implementation in hardware, some optimizations were made. Hence, MISTY1 and KASUMI are very similar, such that the analyzes available on one are easily adapted to the other (kasumi is misty in Japanese, "misty" in English).

KASUMI has a block size of 64 bits and a key size of 128 bits. It is a block cipher unit of type Feistel Cipher with eight turns and, like MISTY1 and MISTY2, has a recursive structure, with subcomponents of type similar to Feistel.

In 2001, Kühn presented an impossible differential attack in six laps of KASUMI.

See also: A5/1 and A5/2