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Navy Signals Code

Tool to decrypt/encrypt with the international maritime/navy signal flags/code automatically to communicate with ships.


Navy Signals Code -

Tag(s) : Communication System, Symbol Substitution

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Navy Signals Code

Navy Signal Flags Decoder

Navy Flags Encoder


Answers to Questions (FAQ)

What is the Nautical Signals Flags alphabet? (Definition)

The International Code of Maritime Signals is a visual communication system used in maritime navigation to transmit messages at a distance between ships or between a ship and the coast. It is made up of a set of flags (pavilions/semaphores) each having a meaning.

How to encrypt using Navy Signals cipher?

The International Maritime Signal Code can be used as a mono-alphabetic substitution cipher, each nautical flag represents a letter of the alphabet or a number from 0 to 9.


Example: 'FLAG' is coded char(70)char(76)char(65)char(71)

The digits have a different shaped flag:


Each ship/boat only carries one set of flags, so if a letter is repeated, it cannot be coded. To deal with this eventuality, there are 4 substitution/repetition flags.

char(107) repeat the first flag

char(108) repeat the second flag

char(109) repeat the third flag

char(110) repeats the fourth flag (not used in the official version of the International code)

Example: SOS is translated char(83)char(79)char(107)

How to decrypt Maritime Signals cipher?

The deciphering of Maritime Signals flags is a substitution between a flag and a letter of the alphabet (or a number).

Example: char(78)char(65)char(86)char(89) is translated NAVY.

Except for the 4 repetition flags which repeat a previous flag.

How to recognize Maritime Flag ciphertext?

The ciphered message is made of flags (squared) in basic colors: blue, white, yellow, red, black (no green and no compound colors) offering a large contrast.

Flags used in the navy, do not necessarily mean a distress signal, they can handle a radio problem and help ship navigation.

All references to the navy, naval forces (Royal Navy, US Navy etc.) and boats, lighthouses or distress situation (use of flare, buoy, whistle) in general are clues.

What are the variants of the Maritime alphabet?

NATO uses 10 other flags (square format) to encode digits.


Why using Maritime Signals Flags?

The International Maritime Signals Flags system is used to facilitate communication between ships, especially when they are at a distance or when they cannot use radio or other electronic means of communication. It is used to transmit messages such as warnings, requests for help, navigation instructions, etc.

What is the reference book for Maritime Signals?

The French reference codebook is available here

This code contains the rules and detailed descriptions of maritime communication signals, flags and procedures used throughout the world.

Source code

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