6.1.4 Encrypted Checksum (Message Authentication Code, MAC)

CryptoMemory® implements a data validity check function in the form of an encrypted checksum. This checksum provides bidirectional data integrity checking and data origin authentication in the form of a Message Authentication Code (MAC). Only the host or device that carried out a valid authentication is capable of computing a valid MAC. When writing data to the CryptoMemory device in Authentication or Encryption communication modes, the host must send a valid checksum immediately following the write command. If the checksum is invalid, the device rejects the write command and resets the device security privileges. The host must reinitiate entry into Authentication and, if applicable, Encryption modes to continue. The use of checksum is optional when reading data. Invoking the Read Checksum command resets the device’s security settings; therefore, it is recommended to use this command only after all data read operations from the device have been completed.