Bazz quote "At normal resolutions the characters in the photo are not visable.
However it would only take seconds for software to find the characters
in the photo."

You do not know what you are talking about, please learn how something works before commenting like that.

Steganography look for a program then try it and come back with a more reasoned response.

Further, if you want to hide something real secret, hide it in a pornographic image, then hide that image in something bigger: even if someone suspects the larger object, they will think that you were merely hiding the pornographic image and won't look any further.

Messages are embedded in photos all the time, a simple one is for glamour shots in magazines to be embedded with the word 'sex' and like short words, particularly of the four letter variety, such embeds were exposed as an advertizing gimmick at least fifty years ago.

This is more up to date:
http://www.psychologistworld.com/influence-personality/subliminal-advertising

Please read before posting nonsense, what Yuyutsu and I are talking about is Steganography.

To simplify it you have a file any file you want to hide it you can hide it inside the data of another file.

For example you want to send someone a .txt document or a .jpg photo (remember any file you like) your file to hide is say 500k in size you get any other file say a .mp4 movie a .bmp picture file a Steganography program will hide the file so people only see 1 file unless you tell them something is inside it they will not know.

A 500k file can easily be hidden inside BUT the smaller the size of the other file the greater the chance of it being detected.

A 1K .txt file in a 20mb music file is going to draw no suspicion,

whereas a 5mb .txt file in the same 20mb music file would be suspicious.

Just read this link, for more info and programs.
http://hackersonlineclub.com/steganography/

Is Mise,
The book code was used a lot in the wartime.
It has a problem in that you have to agree on page line etc personally
as if you send it by mail, telephone etc etc.
With the PGP style programs you just exchange public keys by email.
Everybody has a public key and everyone can send messages to everyone
but no one else in the group can read each others messages.

Philip S, yes I know nothing about Stenography, never used it but even
bits in a sound recording could be found. In a 500kb file it would be
susceptible to a brute force attack, would it not ?
The text of course could be encyphered before input to the sound file.

Bazz Only an idiot would would put something large in a 500kb file.

To use brute force to find something first you have to know which file it is in then you have to know which of the many programs was used to hide something, good luck checking thousands of files.

Also brute force uses word dictionaries, some programs don't use passwords they can use files as the password some even use a password + a file or files + a set of numbers.

Most people would encrypt the .txt file before hiding it, if it was very sensitive info.