zsteg

Description

detect stegano-hidden data in PNG & BMP

Installation

gem install zsteg

Detects:

• LSB steganography in PNG & BMP
• zlib-compressed data
• OpenStego
• Camouflage 1.2.1
• LSB with The Eratosthenes set

Usage

# zsteg -h

Usage: zsteg [options] filename.png [param_string]

    -a, --all                        try all known methods
    -E, --extract NAME               extract specified payload, NAME is like '1b,rgb,lsb'

Iteration/extraction params:
    -o, --order X                    pixel iteration order (default: 'auto')
                                     valid values: ALL,xy,yx,XY,YX,xY,Xy,bY,...
    -c, --channels X                 channels (R/G/B/A) or any combination, comma separated
                                     valid values: r,g,b,a,rg,bgr,rgba,r3g2b3,...
    -b, --bits N                     number of bits, single int value or '1,3,5' or range '1-8'
                                     advanced: specify individual bits like '00001110' or '0x88'
        --lsb                        least significant bit comes first
        --msb                        most significant bit comes first
    -P, --prime                      analyze/extract only prime bytes/pixels
        --shift N                    prepend N zero bits
        --step N                     step
        --invert                     invert bits (XOR 0xff)
        --pixel-align                pixel-align hidden data

Analysis params:
    -l, --limit N                    limit bytes checked, 0 = no limit (default: 256)

        --[no-]file                  use 'file' command to detect data type (default: YES)
        --no-strings                 disable ASCII strings finding (default: enabled)
    -s, --strings X                  ASCII strings find mode: first, all, longest, none
                                     (default: first)
    -n, --min-str-len X              minimum string length (default: 8)

    -v, --verbose                    Run verbosely (can be used multiple times)
    -q, --quiet                      Silent any warnings (can be used multiple times)
    -C, --[no-]color                 Force (or disable) color output (default: auto)

PARAMS SHORTCUT
	zsteg fname.png 2b,b,lsb,xy  ==>  --bits 2 --channel b --lsb --order xy

Examples

Simple LSB

# zsteg flower_rgb3.png

imagedata           .. file: 370 XA sysV pure executable not stripped - version 768
b3,rgb,lsb,xy       .. text: "SuperSecretMessage"

Multi-result file

# zsteg cats.png

meta F              .. ["Z" repeated 14999985 times]
meta C              .. text: "Fourth and last cat is Luke"
meta A              .. [same as "meta F"]
meta date:create    .. text: "2012-03-15T23:32:46+07:00"
meta date:modify    .. text: "2012-03-15T23:32:14+07:00"
imagedata           .. file: 68K BCS executable
b1,r,lsb,xy         .. text: "Second cat is Marussia"
b1,g,lsb,xy         .. text: "Good, but look a bit deeper..."
b1,bgr,lsb,xy       .. text: "MF_WIhf>"
b2,g,lsb,xy         .. text: "VHello, third kitten is Bessy"

wbStego even distributed

# zsteg wbstego/wbsteg_noenc_even.bmp 1b,lsb,bY -v

b1,lsb,bY           .. <wbStego size=22, data="xtSuperSecretMessage\n", even=true, mix=true, controlbyte="t">
    00000000: 51 00 00 16 00 00 74 0d  b5 78 1e a1 39 74 e8 38  |Q.....t..x..9t.8|
    00000010: 53 c6 56 94 75 d1 a5 70  84 c8 27 65 fe 08 72 35  |S.V.u..p..'e..r5|
    00000020: 1f 3e 53 5d a7 65 8b 6e  3b 63 6b 1d bf 72 ee 27  |.>S].e.n;ck..r.'|
    00000030: 65 8d ee 82 74 da 8d 4d  b3 8a 06 65 7e f8 73 9c  |e...t..M...e~.s.|
    00000040: 36 0c 73 aa bd 61 67 29  37 67 5f 0b 06 65 1f a4  |6.s..ag)7g_..e..|
    00000050: 0a a1 f8 35                                       |...5            |

wbStego encrypted

# zsteg wbstego/wbsteg_blowfish_pass_1.bmp 1b,lsb,bY -v

b1,lsb,bY           .. <wbStego size=26, data="\rC\xF5\xBF#\xFF[6\e\xB3"..., even=false, hdr="\x01", enc="Blowfish">
    00000000: 1a 00 00 00 ff 01 01 0d  43 f5 bf 23 ff 5b 36 1b  |........C..#.[6.|
    00000010: b3 17 42 4a 3f ba eb c7  ee 9c d7 7a 2b           |..BJ?......z+   |

zlib

# zsteg ndh2k12_sp113.bmp -b 1 -o yx -v

b1,rgb,lsb,yx       .. zlib: data="%PDF-1.4\n%\xC3\xA4\xC3\xBC\xC3\xB6\xC3\x9F\n2 0 obj\n<</Length 3 0 R/Filter/FlateDecode>>\nstream\nx\x9C\x8DT\xC9n\xDB@\f\xBD\xCFW\xF0\x1C \x13\x92\xB3\x03\x86\x80\xC8K\xD1\xDE\\\b\xE8\xA1...", offset=4, size=186
    00000000: 00 02 eb 9b 78 9c d4 b9  65 54 24 cc 92 36 58 b8  |....x...eT$..6X.|
    00000010: d3 68 e3 ee ee 4e e3 ee  ee 0e 85 bb 3b dd 68 23  |.h...N......;.h#|
    00000020: 8d bb bb bb 3b 8d bb bb  3b 34 ee 6e 1f ef 7b ef  |....;...;4.n..{.|
    00000030: 9d 3b b3 e7 cc 9e d9 3d  df 9e dd cd 8a 1f 99 19  |.;.....=........|
    00000040: 99 55 11 99 4f 58 25 99  82 88 18 1d 13 3d 2b 2c  |.U..OX%......=+,|
    00000050: 59 6f 7e 6f 7b 6f 63 6f  16 2c 33 21 23 a1 9d 91  |Yo~o{oco.,3!#...|
    00000060: 25 2c 2f 2f 83 0c d0 d6  cc d9 9c 90 e5 73 46 89  |%,//.........sF.|
    00000070: 41 cc c2 da 19 e8 c8 20  66 6d e8 0c 14 01 1a db  |A...... fm......|
    00000080: 99 00 f9 f8 60 9d 9c 1d  81 86 36 b0 ee e9 bf 54  |....`.....6....T|
    00000090: 86 6d 57 05 e0 3b 26 d5  2f 71 09 51 63 eb c0 82  |.mW..;&./q.Qc...|
    000000a0: bf 0f 49 4f 6f e8 40 ff  c9 f9 43 25 1d 9e 6b 1b  |[email protected]%..k.|
    000000b0: a3 73 fd 42 c4 a6 65 3d  ef 0a 07 32 17 2d dc f9  |.s.B..e=...2.-..|
    000000c0: 10 8c 0d 4b d7 9d e6 01  12 4f 11 6f f0 cd 64 f2  |...K.....O.o..d.|
    000000d0: f2 19 5c df 76 eb 01 49  dc fd cd 76 65 a2 3a 8a  |..\.v..I...ve.:.|
    000000e0: fd bb 13 a9 e6 3a c9 da  19 34 ae f0 43 bb 90 90  |.....:...4..C...|
    000000f0: 58 88 de 46 ce 91 6f aa  8d d9 7d b8 d6 88 a6 65  |X..F..o...}....e|

See also

1. https://29a.ch/photo-forensics/
2. https://holloway.nz/steg/

License

Released under the MIT License. See the LICENSE file for further details.