KASUMI

KASUMI is a block cipher with a 128-bit key and 64-bit input and output, built around an eight-round Feistel network. It is used in third-generation mobile communications: in UMTS it provides the confidentiality and integrity algorithms known as UEA1 and UIA1, in GSM it underlies the A5/3 and A5/4 key stream generators, and in GPRS it underlies the GEA3 and GEA4 generators. It was designed for the 3GPP standards effort by the Security Algorithms Group of Experts (SAGE), part of the European standards body ETSI. Because of schedule pressure, SAGE based it on the existing MISTY1 cipher, developed and patented by Mitsubishi Electric, and modified it for easier hardware implementation. The name comes from the Japanese word for mist, a nod to MISTY1. In January 2010 Orr Dunkelman, Nathan Keller and Adi Shamir published a related-key attack that breaks KASUMI with very modest computational resources; the attack is ineffective against MISTY1.