The message authentication code generated by the authentication process. The field consists of 4 hexadecimal coded characters (i.e., characters from the set 0..9, A..F), a separator character (space ), and 4 hexadecimal coded characters. When authentication is not used, this field shall be filled with the space character for the minimum field length. The separator character is the ASCII space character during interchange. For archiving purposes the separator character can be set to another value to represent success or failure of the authentication process.