Patent Document ID: 7796752
Application ID: 10286800
Patent Flag: 1

Claim One:
1. A method implemented in a mobile communication device, the method comprising: providing a key variable to a partial KASUMI block cipher, wherein said partial KASUMI block cipher implements only a fraction of all eight rounds of a full KASUMI block cipher and executes only a first round and a second round of said full KASUMI block cipher, and wherein an output of said partial KASUMI block cipher is not an output of a last round of said full KASUMI block cipher and is an output of said second round of said full KASUMI block cipher; using a first logic circuit to combine said output of said partial KASUMI block cipher with an output of a first register, wherein said first logic circuit does not compute one or more KASUMI rounds; wherein an output of said first logic circuit is coupled to an input of said partial KASUMI block cipher; generating a keystream block by using only one operation of said partial KASUMI block cipher, and without utilizing a full KASUMI block cipher, wherein generating said keystream block comprises: processing said input of said partial KASUMI block cipher by executing less than all eight rounds of said full KASUMI block cipher to generate said output of said partial KASUMI block cipher; setting said keystream block to said output of said second round of said partial KASUMI block cipher, wherein said keystream block is not set to said output of said last round of said full KASUMI block cipher.