Steganography

Steganography Techniques 

Steganography
hiding information within other file like pictures,audio,text,...etc

 

Classification of steganography
technical: using physical or chemical means to hide the existence of a message
linguistic: utilizing natural language to hide the message

Technical steganography
invisible ink
microdots
computer-based methods

Linguistic steganography
semagrams: utilizing visual symbols or signs to hide secret messages
open codes: utilizing a designed pattern on the document to hides the secret message

...

Semagrams

visual semagrams:
using innocent-looking or everyday physical objects to convey a message

ex:
symbols, doodles or the positioning of items on a desk or Website

text semagrams: hides a message by modifying the appearance of the carrier text
ex:
subtle changes in font size or type, adding extra spaces, or different flourishes in letters or handwritten text.

...

Open codes 

jargon code: using a language that a group of people can understand
ex:
define: eat=email to, cow=raymond
message: eat cow
plaintext: email to raymond

covered ciphers: the message is hidden openly in the carrier medium
 null ciphers
 grille ciphers

 
null ciphers:
plaintext is mixed with a large amount of material
ex:
key: 1,2,3,1,2,3,1,2,3,1,2 [each letter in each word]
message: Susan sAys GaIl Lies. MAtt leTs Susan fEel joVial. Elated (or) aNgry?
plaintext: Sail at seven.

grille ciphers:
looking plaintext by cutting holes in a piece of paper with a large amount of maerial


refer
www.garykessler.net/library/fsc_stego.html
https://en.wikipedia.org/wiki/Null_cipher

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Common type of steganography
image steganography
document steganography
audio steganography: it is hard to find secret message
video steganography: it is hard to find secret message

Audio steganography method
echo data hiding
spread spectrum method
Low Bit encoding
Phase coding

...

Common tool
Fort Knox
Blindside - 將任何檔案藏在Bitmap
S-Tools
Steghide - 壓縮 ,加密,checksum
Digital Identity
Stegowatch - 偵測是否有藏資料
Image Hide - 檔案大小不會改變
Mp3Stego - 將資料藏在壓縮的mp3
snow - 將資料藏在空白處

refer
http://wenku.baidu.com/view/da7fbcd0360cba1aa811da11.html?re=view

 

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Image Steganography
BMP tool 

tool: stool.exe
insert secret text in BMP by LSB
reveal:get secret

ps:
orginal bmp and new bmp:size is same,hash is not same


LSB演算法
大小不會增加,因為是取代少部份字元
常用在BMP

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JPG tool

tool: jphide  
加內容進jpeg by DCT
jphide.exe < secret file> < original file>
ex:
jpseek.exe xx.jpg

tool: jpseek 
解內容from jpeg
jpseek.exe < new file> < secret file>

DCT(Discrete cosine transform,離散餘弦變換)
a technique is used by JPEGs for compression

ps:
orginal jpg and new jpg:size is not same

...

Detection tool

tool: stegdetect
偵測有沒有screat在裡面
stegdetect [parameter] < file path>
ex:
stegdetect -t p xx.jpg
stegdetect *.jpg

tool: stegbreak
用字典檔解密並輸出screat
ex:
stegbreak -r rules.ini -f password.lst xx.jpg

 

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Image compression
lossy compression :破壞性資料壓縮
lossless compression: 非破壞性資料壓縮

Image type
raster image: it is made of up pixels, each a different color, arranged to display an image.
ex: BMP,PNG,JPG
vector image: it is made up of paths, each with a mathematical formula (vector) that tells the path how it is shaped and what color it is bordered with or filled by.
ex:SVG
Metafile image: a formats containing both pixel and vector data
ex:EPS, PDF

refer
https://www.psprint.com/resources/difference-between-raster-vector/
https://en.wikipedia.org/wiki/Image_file_formats


Common graph file
BMP - Microsoft Windows bitmap
DIB - Microsoft Windows Device Independent Bitmap
EPI - Adobe Encapsulated PostScript Interchange format
EPS - Adobe Encapsulated PostScript
GIF - CompuServe Graphics Interchange Format
JPC - JPEG-2000 Code Stream Syntax
JPEG - Joint Photographic Experts Group JFIF format
PCD - Photo CD
PCX - IBM PC Paintbrush file
PDB - Palm Database ImageViewer Format
PDF - Portable Document Format
PGM - Portable graymap format (gray scale)
PICT - Apple Macintosh QuickDraw/PICT file
PNG - Portable Network Graphics
PSD - Adobe Photoshop bitmap file
SVG - Scalable Vector Graphics
TGA - Truevision Targa image
refer
http://www.online-utility.org/image_converter.jsp

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GIF
8bit RGB bitmap image format
up to 256 distinct colors
lossless compression
refer
https://zh.wikipedia.org/wiki/GIF

...

BMP(Bitmap)
a Raster image
https://zh.wikipedia.org/wiki/BMP

bitmap contains below
file header
color table/RGBQUAD array:specifies the dimensions,compression type,color format,...etc
information header
image data

...

JPG(Joint Photographic Experts Group)
一種針對相片影像而廣泛使用的一種失真壓縮標準方法
refer
https://zh.wikipedia.org/wiki/JPEG

 

 

2015-10-19 15:35:22發表 2015-10-19 15:35:59修改   

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