Steganography means "hidden writing", where we send messages in hidden ways. Does this mean that something only experts can understand is called steganography?
No. For it to be steganography, the message must be hidden in something (an image, a file, etc). When someone looks at that something, they should not be able to suspect that it contains a hidden message.
This isn't the case for morse code at all. There is no carrier that hides a message, there is just the message itself.
At some level, Steganography implies concealing a message within another. The root Greek word steganos means concealed within graphein writing.
The understanding of the message is not restricted to experts. Rather it is security by obscurity that only the target recepient(s) can read.
Morse code is just a way of representing information. It does not imply any secrecy, the reversal is well known.
However, you could hide messages by encoding it in Morse code and then placing it within a public message.
-- --- .-. ... . .. ... -. --- - ... - . --. .- -. ---
Short answer: no. Encodings are not steganography.
Morse Code is the precursor to how modern day computers transmit information:
- letters -> ascii values ('a' -> "97")
- ascii values -> binary strings ("97" -> "0110 0001")
- binary strings -> square waves of high and low voltage ("0110 0001" -> "_--____-")
There's nothing secretive here, we've just used a standardized system for turning text into something that's transmittable over a wire. That's called an encoding, there's no secrets.
Steganography, on the other hand is hiding information within another message so that even a trained observer is unlikely to notice that the hidden message even exists. Here's a toy example of hiding "Hi nsa" inside a seemingly unrelated message.
Hiding information's not so arduous.
You could certainly use Morse Code as part of steganography, like this example from wikipedia/steganography, but an encoding scheme by itself is not steganography:
Jeremiah Denton repeatedly blinked his eyes in Morse Code during the 1966 televised press conference that he was forced into as an American POW by his North Vietnamese captors, spelling out "T-O-R-T-U-R-E". This confirmed for the first time to the U.S. Military (naval intelligence) and Americans that the North Vietnamese were torturing American POWs.
Morse code is simply an encoding. Steganography means that the fact that a communication channel exists is hidden (hence, embedding in images, etc.)
The famous "blinking of messages" is steganography because the communication channel is hidden. The encoding used (i.e. morse code) is secondary.
Yes, the encoding method needs to be understood, but as soon as you realise that the message is using the Morse encoding, you can simply look up the decoding key and decode the message. Other encodings could be used.
There is another famous example when the US military used Navajo speakers to transmit sensitive data over the radio. While only another Navajo speaker could understand the communication (a relatively small set of people), it is very obvious that communication was occurring. This is also not steganography.
Morse code itself isn't steganography, but it's not incompatible with steganography. The key is that the Morse itself isn't the important message – there's something else hidden in there. For example, if we were sending Morse code between computers, then perhaps you could encode messages by adjusting the length of the dits and dahs by very small amounts, or by making small pitch changes if it were audible. The Morse message would remain identical, but it could be used to hide a very different message.
The goal of steganography is to hide the fact that a message exists. If I hear a complex series of bips and beeps, then I'm going to guess that it's probably a message, and then I can start trying to figure out what it means.
But if you were to cleverly hide Morse code in the background music of a popular song, in a way that most people wouldn't even notice but Morse code experts would hear plain as day... that would be steganography.
Money diluting before Havana that.
This is steganography using the morse code. Can you guess what's the hidden message?
Remove consonants and convert
a,e -> SHORT,
i,o,u -> LONG. You get
Money diluting before Havana that
O E / I U I / E O E / A A A / A
- - / - - - / . - . / . . . / .
M O R S E
However, the plain Morse code is what it is: a coding.
You should distinguish between cryptography and steganography. Cryptography means that the content of the message is kept confidential, but the very fact of the message being sent is known to outsiders. Steganography goes even further to hide the mere fact of communication, possibly also using cryptography in the process.