Steganography Tool

Concept

LSB (Least Significant Bit) image steganography in Go. Embeds a length-prefixed payload into the red channel of PNG pixels.

Objective

Implement a covert channel by modifying the least significant bits of image pixel data, then verify extraction round-trips cleanly.

Constraints

Payload size limited to (width × height) / 8 bytes minus the 4-byte length header. Not robust against JPEG re-encoding or image resizing.

Go
Cryptography
Image Processing

Source code · original languagesrc/main.go

1package main23import (4	"encoding/binary"5	"fmt"6	"image"7	"image/color"8	"image/png"9	"os"10)1112func embed(img *image.NRGBA, payload []byte) error {13	header := make([]byte, 4)14	binary.BigEndian.PutUint32(header, uint32(len(payload)))15	bits := append(header, payload...)1617	idx := 018	for y := img.Bounds().Min.Y; y < img.Bounds().Max.Y; y++ {19		for x := img.Bounds().Min.X; x < img.Bounds().Max.X; x++ {20			if idx >= len(bits)*8 {21				return nil22			}23			c := img.NRGBAAt(x, y)24			bytePos, bitPos := idx/8, uint(7-idx%8)25			bit := (bits[bytePos] >> bitPos) & 126			c.R = (c.R & 0xFE) | bit27			img.SetNRGBA(x, y, color.NRGBA{R: c.R, G: c.G, B: c.B, A: c.A})28			idx++29		}30	}31	if idx == len(bits)*8 {32		return nil // The payload filled the image exactly.33	}34	return fmt.Errorf("image too small for payload")35}3637func main() {38	f, _ := os.Open("cover.png")39	defer f.Close()40	src, _ := png.Decode(f)4142	dst := image.NewNRGBA(src.Bounds())43	for y := dst.Bounds().Min.Y; y < dst.Bounds().Max.Y; y++ {44		for x := dst.Bounds().Min.X; x < dst.Bounds().Max.X; x++ {45			dst.Set(x, y, src.At(x, y))46		}47	}4849	_ = embed(dst, []byte("HIDDEN_MESSAGE"))5051	out, _ := os.Create("stego.png")52	defer out.Close()53	png.Encode(out, dst)54	fmt.Println("Done — payload embedded into stego.png")55}

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