---
# System prepended metadata

title: 'picoCTF: St3g0           '
tags: [picoCTF]

---

```shell
┌──(kali㉿kali)-[~/code]
└─$ zsteg -a pico.flag.png | grep "pico"
b1,rgb,lsb,xy       .. text: "picoCTF{7h3r3_15_n0_5p00n_a9a181eb}$t3g0"
...
(Omit)
```
- ref:
https://github.com/zed-0xff/zsteg
(main point: install with the command:`gem install zsteg`)
    - usage:
```shell
    ┌──(kali㉿kali)-[~/code]
└─$ zsteg            
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
        --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
```
