code: def to_string(self):
          
          #define UID_SIZE		6	/* Size of secret ID field */
          #define FIXED_SIZE              16      /* Max size of fixed field */
          #define KEY_SIZE                16      /* Size of AES key */
          #define KEY_SIZE_OATH           20      /* Size of OATH-HOTP key (key field + first 4 of UID field) */
          #define ACC_CODE_SIZE           6       /* Size of access code to re-program device */
          #
          #struct config_st {
          #    unsigned char fixed[FIXED_SIZE];/* Fixed data in binary format */
          #    unsigned char uid[UID_SIZE];    /* Fixed UID part of ticket */
          #    unsigned char key[KEY_SIZE];    /* AES key */
          #    unsigned char accCode[ACC_CODE_SIZE]; /* Access code to re-program device */
          #    unsigned char fixedSize;        /* Number of bytes in fixed field (0 if not used) */
          #    unsigned char extFlags;         /* Extended flags */
          #    unsigned char tktFlags;         /* Ticket configuration flags */
          #    unsigned char cfgFlags;         /* General configuration flags */
          #    unsigned char rfu[2];           /* Reserved for future use */
          #    unsigned short crc;             /* CRC16 value of all fields */
          #};
          t_rfu = 0
  
          first = struct.pack('<16s6s16s6sBBBBH',
                              self.fixed,
                              self.uid,
                              self.key,
                              self.access_code,
                              len(self.fixed),
                              self.extended_flags.to_integer(),
                              self.ticket_flags.to_integer(),
                              self.config_flags.to_integer(),
                              t_rfu
                              )
  
          crc = 0xffff - yubico_util.crc16(first)
  
          second = first + struct.pack('<H', crc) + self.unlock_code
          return second
docs: Return the current configuration as a bytestring (always 64 bytes).