png-steganography

This encoding is easily detected (data is hidden in the last few bits of every pixel's channel) - do not use for sensitive data.

• To output help info use -h
• To output license info use -l - this program is licensed under gpl-3-or-later

Installation

If you have golang installed

go install codeberg.org/oliverd/png-steganography@latest

This will install in GOPATH/bin

Or download the latest binaries from releases

Basic usage

# uses 2 bits per channel, example.png should be in the current directory
png-steganography -i example.png -d "hello" -o hidden.png -b 2* # Encode data to hidden.png using example.png as a base
png-steganography -i hidden.png -b 2* # Decode data in hidden.png

Channel options

# uses 3 bits from the blue channel and 2 bits from the others. Data will be stored in order Blue, Red, Green
png-steganography -i example.png -d "hello" -o hidden.png -b 3,2,2 -c BRG
png-steganography -i hidden.png -b 3,2,2 -c BRG

note * repeats the last values the required times e.g -b 2* is equivalent to -b 2,2* or even -b 2,2,2,2

Formatting

png-steganography -i example.png -d "48656C6C6F20576F726C640A00" -o hidden.png -b 2* -f hex # -d will use hexadecimal,
png-steganography -i hidden.png -b 2* -f hex # data will be output in hexadecimal
png-steganography -i hidden.png -b 2* # data will be output as a string

Options for -f (these can be used to specify the encoding of -d or the output)

• hex: hexadecimal
• str: string (Null terminated)
• b64: base64
• bin: same as string but will ignore NULL

Other options

• -a all: decoder will read the last binary data even if it is not a whole byte (if the string mode is used Null will still be respected)
• -p padding: how many bits should be skipped in the writable components - in encoding mode these bits will not be changed
• -r rounding mode: t: truncate, n: nearest
• -t type: what image type do you want to encode/decode color: C32, C64 or grey: G8, G16 or alpha: A8, A16

Faq

Output is gibberish

• -b needs to be passed the correct number of bits for each channel
• Check what ordering the channels use for your input image, program default is RGBA, for example you could change the alpha channel to be first by passing -c ARGB

Only partial output

If the default string mode encounters a null byte it will terminate - You can pass -f bin to prevent this behavior

Illegal base64 data

There needs to be a multiple of 4 characters in base64. Use = to pad

Building

Note: This package only depends on the Go standard library

Clone repo (you need to be your src directory GOPATH/src)

git clone https://codeberg.org/oliverd/png-steganography
cd png-steganography # need to be in directory for following commands

Run your version

go run . -i example.png -d "hello" -o hidden.png -b 2*
go run . -i hidden.png -b 2*

Build and install (command line png-steganography will now use your version)

# -w -s to strip debug symbols, panics will still be readable
go install -ldflags "-w -s" .

Compile to all targets

go install github.com/mitchellh/gox@latest # only need if you don't have gox yet
gox -output "build/{{.Dir}}_{{.OS}}_{{.Arch}}" -ldflags "-w -s"

This documentation can be reused under GPL-3-or-later or CC-SA-4.0 - (C) Oliver Day