The TOI payload, prior to encryption, is 165 bits in length. Conforming to the AES Encryption scheme with a 128-bit cipher key, the encrypted part of the payload then effectively becomes 256 bits in length to create blocks of 128 bits. This results in a 2 slot broadcast binary message.
NOTE: TOI messages are repeated every 15 seconds, until cancelled locally. Cancelling a TOI locally stops transmission of TOI message repetitions. Remote units receiving a TOI will apply Lost Target/Auto Drop processing rules to remove the TOI designation from a target.
|
Parameter |
Number of bits |
Description |
Encryption Status |
|
DAC |
10 |
Identifier for this message: 366 |
Unencrypted |
|
Function ID |
6 |
Function Identifier: 58 |
Unencrypted |
|
Source ID (MMSI) |
30 |
Source MMSI number. |
AES encrypted |
|
Target Type |
4 |
1 = AIS, 2 = ARPA, 3 = Dead Reckoned |
AES encrypted |
|
Target ID |
30 |
MMSI if type is 1, Sender generated ID otherwise |
AES encrypted |
|
SOG |
10 |
Speed over ground in 1/10 knot steps (0-102.2 knots) 1023 = not available, 1022 = 102.2 knots or higher. |
AES encrypted |
|
Longitude |
28 |
Longitude in 1/10 000 min (±180 degrees, East = positive, West = negative. 181 degrees (6791AC0 hex) = not available = default) |
AES encrypted |
|
Latitude |
27 |
Latitude in 1/10 000 min (±90 degrees, North = positive, South = negative, 91 degrees (3412140 hex) = not available = default) |
AES encrypted |
|
COG |
12 |
Course over ground in 1/10 (0-3599). 3600 (E10 hex) = not available = default; 3 601 – 4 095 should not be used. |
AES encrypted |
|
Checksum |
8 |
Exclusive OR (XOR) 8-bit |
AES encrypted |
|
Stuffed bits |
107 |
Stuffed bits are inserted so that the number of bits in the encrypted field is a multiple of 128 bits (256 for this message); set to zero. |
AES encrypted |
|
TOTAL |
272 |
16 unencrypted bits plus 256 encrypted bits |
|
