The ATSHA204 can generate high-quality random numbers and employ them for many purposes. When the random number is used as part of the system protocol, every ATSHA204 transaction is guaranteed to be unique, completely preventing any type of replay attack. Every ATSHA204 ships with a guaranteed unique 72-bit serial number that is securely stored inside the device. Using the cryptographic protocol, the host system or a remote server can prove that the serial number is authentic.