Patent ID: 8090098

Claim:
A computer implemented method of generating a Message Authentication Code (MAC) by a processor using a stream cipher, comprising the steps of: (a) dividing an input message M into k n-bit message blocks, wherein k is an integer number, wherein each of the respective divided input message blocks have a unique integer number represented by the respective K integer number; (b) encrypting by a processor each of the respective divided input message blocks using a result obtained by exclusive-ORing (XORing) with a different key, wherein the results by XORing each of the divided input message blocks has a different key from any of the other divided input message blocks, wherein each of the different keys is configured with a secret key K MAC for MAC generation with the unique integer number associated with the respective divided input message block, calculating respective intermediate values, and wherein in step (b), the respective intermediate values hi are calculated by the following formula: h i =E n ( K MAC ⊕i,m i ), wherein the k n-bit message blocks obtained by dividing the input message M are denoted by m 1 , m 2 , . . . , mk, one of the message blocks is denoted by mi, and En(K, mi) denotes an encryption algorithm performed for the message blocks mi using K as a key by the key stream generator; and c) XORing the respective intermediate values resulting from step (b); and (d) encrypting, at a key stream generator, the result of step (c) using the secret key K MAC for MAC generation and generating a MAC.