Editing Steganography (section)

=== Digital messages ===
[[Image:Steganography original.png|frame|Image of a tree with a steganographically hidden image. The hidden image is revealed by removing all but the two least significant [[bit]]s of each [[color component]] and a subsequent [[Normalization (image processing)|normalization]]. The hidden image is shown below.]] 
[[Image:Steganography recovered.png|frame|Image of a cat extracted from the tree image above.]]

Since the dawn of computers, techniques have been developed to embed messages in digital cover mediums. The message to conceal is often encrypted, then used to overwrite part of a much larger block of encrypted data or a block of random data (an unbreakable cipher like the [[one-time pad]] generates ciphertexts that look perfectly random without the private key).

Examples of this include changing pixels in image or sound files,<ref>{{cite journal|doi=10.1016/j.sigpro.2009.08.010|title=Digital image steganography: Survey and analysis of current methods|journal=Signal Processing|volume=90|issue=3|pages=727–752|year=2010|last1=Cheddad|first1=Abbas|last2=Condell|first2=Joan|last3=Curran|first3=Kevin|last4=Mc Kevitt|first4=Paul|bibcode=2010SigPr..90..727C }}</ref> properties of digital text such as spacing and font choice, [[chaffing and winnowing]], [[mimic function]]s, modifying the echo of a sound file (echo steganography).{{citation needed|date=April 2024}}<!-- Original citation irretrievably lost -->, and including data in ignored sections of a file.<ref>{{cite journal | last1= Bender | first1= W. | last2= Gruhl | first2= D. | last3= Morimoto | first3= N. | last4= Lu | first4= A. | title= Techniques for data hiding | journal= IBM Systems Journal | publisher= IBM Corp.| date=1996 | volume= 35 | issn= 0018-8670 | url= https://pdfs.semanticscholar.org/8c82/c93dfc7d3672e58efd982a23791a8a419053.pdf | archive-url= https://web.archive.org/web/20200611050549/https://pdfs.semanticscholar.org/8c82/c93dfc7d3672e58efd982a23791a8a419053.pdf | url-status= dead | archive-date= 11 June 2020 |issue = 3.4| pages=313–336| doi= 10.1147/sj.353.0313 | s2cid= 16672162 }}</ref>

{{Multiple image
|align=center
|direction=horizontal
|header=Images hidden in sound files
|image1=Drawing of the word Wikipedia in Coagula.jpg
|caption1=1. The word "Wikipedia" is drawn using computer software
|alt1=The word "Wikipedia" written in green and red on black background
|width1=250
|image2=Drawing of the word Wikipedia transformed into a wav file (Coagula software).wav
|caption2=2. The image is converted into an audio file
|alt2=
|image3=Wikipedia wavefile by Coagula - logarihtmic spectrogram.svg
|caption3=3. Finally, the audio is analysed through a spectrogram, revealing the initial image
|alt3=The word "Wikipedia" in yellow over a dark blue/black background
|width3=250
|image4=Spectrogram - Nine Inch Nails - My Violent Heart.png
|caption4=[[Spectrogram]] of a [[Easter egg (media)|hidden image]] encoded as sound in the song "My Violent Heart" by [[Nine Inch Nails]] from the ''[[Year Zero (album)|Year Zero]]'' album (2007)
|alt4=image of a blue arm and hand over white, pixelated dots
|width4=200
}}