In a wireless communication system, a method and system for implementing
an FO function in a KASUMI algorithm for accelerating cryptography in
GSM/GPRS/EDGE compliant handsets are provided. An efficient
implementation of the FO function may comprise circuitry provided for a
pipeline state machine, an FI function, a controller, a pipe register,
and an XOR operation. Signals may be generated to control each round of
FI processing and to indicate when each round is complete. The pipeline
state machine may provide data input and subkey to the FI function for
processing. A first and a second round FI processing outputs may be
transferred to the pipe register. The second round output may be clocked
from the pipe register to generate a portion of the FO function output
and may also be XORed with a third round output of FI processing to
generate the remaining portion of the FO function output.