What is Morse code and how does it encode information?

A system using dots (short signals) and dashes (long signals) to represent letters and numbers — designed by Samuel Morse in the 1830s for telegraph communication A secret code invented by a man named Morse for military communications only A type of shorthand using dots and dashes that only trained stenographers can read A binary code where dots represent 0 and dashes represent 1

What is a 'pigpen cipher' (also called the Freemason cipher)?

A substitution cipher that replaces letters with symbols based on their position in a grid — each letter's symbol is the shape of the grid section containing it A cipher invented on farms where coded messages were hidden in pigpens A children's game where players try to decode messages from pig noises A cipher that uses the letters P, I, G to encode all messages

What is a 'null cipher' (null steganography)?

Hiding a message within a normal-seeming text by using a rule like 'read every third word' or 'take the first letter of every sentence' A cipher that encodes the message as a series of null values (zeros) A failed cipher that has no meaning — all the symbols are null Sending no message at all as a signal — silence is the code

What is a 'book cipher' and what makes it difficult to break?

A cipher where the key is a specific book — numbers in the message refer to page, line, and word numbers in that book — security depends entirely on the attacker not knowing which book is used A cipher where the encryption algorithm is described in a published book A very old cipher that was documented in early cryptography textbooks A cipher that can only be broken by someone who has read many books

What is 'semaphore' and how does it encode information?

A visual signaling system using flags (or lights) held in different arm positions to represent letters and numbers — each position combination maps to a specific character A type of cipher where messages are sent using a flashing light An ancient Greek warning system that used fire signals to communicate across hills A code used in competitive sports to signal plays without speaking

What makes a hidden message different from an encrypted message?

A hidden message uses steganography — concealing that a message exists at all; an encrypted message is visible but unreadable — both can be combined for stronger security There is no difference — hidden and encrypted mean the same thing in cryptography Hidden messages are more secure than encrypted ones because they can't be found An encrypted message is completely invisible; a hidden message can still be seen

What is a 'codebook' and how was it used historically?

A dictionary-like reference where words and phrases are replaced with pre-assigned code words or numbers — both sender and receiver must have the same codebook A book that teaches you how to write codes — a textbook for codemakers A computer program that automatically decodes encrypted messages A list of all known cipher types and how to break them

What is 'invisible ink' and how does it work as a form of steganography?

Writing with substances that are invisible normally but revealed by heat, UV light, or chemical reaction — the message appears blank, hiding the fact that a message exists Very light pencil writing that can be erased after reading Writing in a language that looks like scribbles to untrained readers Ink that fades after a few hours, destroying the message automatically

What is a 'microdot' in the context of secret communications?

A photograph reduced to the size of a printed period that can be hidden in a letter, newspaper, or book — the entire content of a page can hide invisibly in a punctuation mark A very small dot used in pixel art to represent encrypted data A form of braille writing so small that only magnification can reveal it A tiny transmitter hidden in everyday objects used by spies

What is 'binary steganography' (hiding data in digital files)?

Hiding secret data in the least-significant bits of digital files (images, audio, video) — changing these bits creates imperceptible alterations while concealing potentially large amounts of data Converting secret messages to binary (0s and 1s) to hide them in plain numbers Hiding messages only in binary files, not in text files or documents A method of steganography that uses both binary code and standard text together