There is one final part of the data-transmission process that needs to be mentioned due to the fact that it adds additional data to the packet. This is the CRC, or Cyclic Redundancy Checksum value.
When a packet is sent across a network, there has to be a way for the receiving party to know that the packet was not altered or corrupted in transmission. This is accomplished via the CRC. Before the data is packaged and sent, a value is calculated by the CRC algorithm that is based on the bytes of the data. This value is then appended to the actual data and sent to the receiving party. Once the packet is received, the CRC value is removed, and a NEW CRC value is calculated on the received data. If the NEW CRC value matches the ORIGINAL CRC value, the packet is assumed to be complete; otherwise, the packet is considered corrupted and is dumped. As you will see next, this does affect the whole encryption process.