Glossary

CRC is a simple and fast error detection code, based on a polynomial long division operation.

In real life, CRC is calculated for a block of bytes you wish to protect. When the time comes to check the validity of the bytes for errors, you recalculate the CRC for the block and then match the block with the CRC value you have for it. If the values match, then there is a high probability that the data matches as well.

CRC is commonly used due to the small signature size it generates and the speed of the calculation itself. It does not have the cryptographic strength required for signed signatures, but it is useful for communication and storage applications.

In the context of communication protocols, CRC is usually used in one of two ways:

1. For IP-based protocols, UDP and TCP packets have a CRC checksum in them. Packets with wrong checksum values for their CRC get ignored in UDP and get retransmitted on TCP.
2. For circuit-switched protocols, such as 3G_324M, CRC values are embedded into the adaptation layer level of logical channels.