Patent ID: 6442161
Filing Date: 2002-08-27
Classification: H04L

Abstract:
Apparatus for the alteration and output of an input data packet in a computer network, the data packet comprising communication data, and check data, the check data bearing a predetermined relationship to the communication data whereby integrity of the data packet is checked, the apparatus comprising:means arranged to alter the communication data of the input data packet; storage means arranged to store said data packet such that said communication data may be output from said storage means in either an unaltered or altered condition; output means arranged to receive from said storage means said communication data in its altered condition, to determine new check data on the basis of said communication data in its altered condition, and to output said communication data in an altered condition and said new check data as an output data packet; and checking means arranged to receive from said storage means said communication data in its un-altered condition and said check data of said input packet, to determine whether said received check data bears said predetermined relationship to said un-altered communication data, and to give an indication, if it does not to said output means; said output means being further arranged to corrupt said output data packet if said indication is received.