The incoming CIPH_MOD_CMD message triggers the mobile station to enable ciphering of all outgoing data and deciphering of all incoming information. The algorithm A5 uses the current value of the frame number (FN) at the time tx together with the ciphering key Kc as input parameters. The output of this operation are the so-called ciphering sequences, each 114 bits long. As shown in the figure below, the first ciphering sequence and the 114 bits of "useful data" of a burst are XORed to provide the encrypted 114 bits that are actually sent over the air-interface. Note that the ciphering sequences are altered with every frame number, which in turn changes the encryption with every frame number.