Methods for adjusting an m-bit CRC of sub-messages are provided. Such adjustments
enable the computation of the CRC of a message by XORing the partial or incremental
CRCs of composite sub-messages corresponding to the sub-messages. In a first method,
the contents of an m-bit memory location are field squared and stepped to the next
state as determined by the Galois field generated by the CRC generating polynomial
to adjust the m-bit CRC. In a second method, the partial m-bit CRC of a sub-message
is calculated according to CRC generating polynomial, P(x). A variable Y is calculated
using a lookup table, where Y=xn modulo P(x). The partial m-bit CRC
and Y are multiplied together and divided by P(x). The remainder of the division
forms the adjusted m-bit CRC.
