The concept is easy and creative: get the data from the file, encode into base64, compact and encode it again into hexadecimal, then get each chunks of hexa values (ex: ff 12 d3) to compose the RGB pixels (ex: #ff12d3) that represents the data as an encoded PNG image in such a way that it can be reversed and decoded as the original file.
This was a prove of concept written in Ruby so I could upload 6GB of videos and PDFs to Flickr as images, and then get it back as the original files.
[Julian Assange, Cypherpunks 6.3MB PDF as a decodable 4MB PNG]
Simple text encoding sample:
"extrapolo".to_b64.compact.to_hex
=> "78da8b8ac83048ce752b4f32aa28e302001fbe0464"
final 7 hexa color pixels to represent "extrapolo" data as image
=> #78da8b #8ac830 #48ce75 #2b4f32 #aa28e3 #02001f #be0464
and back to the original data,
"78da8b8ac83048ce752b4f32aa28e302001fbe0464".from_hex.unzip.from_b64
=> "extrapolo"
So, "extrapolo" as a PNG image:
More at: http://en.wikipedia.org/wiki/Steganography
Encode: ~45.0× faster (1.9041 s / 0.0423 s)
Decode: ~126.8× faster (1.0655 s / 0.0084 s)
A Rust implementation is included (now optimized) and can still decode the legacy Ruby PNGs.
Current encoding pipeline (optimized):
- zstd compression
- raw compressed bytes packed directly into RGB pixels (no base64/hex)
- tight rectangular dimensions (no forced square)
- PNG text metadata: Author, Title, PayloadLength
- RGB output (no alpha) for smaller images
Build and run:
cargo build --release
./targets/release/steganos
Encode any file into a PNG:
$ steganos encode path/to/input.bin
Sample:
$ steganos encode cypherpunks.pdf
- Encode time: 0.225 s
- Encode sizes: input 6.261 MB, output 3.818 MB
$ steganos decode out-cypherpunks.pdf.png
- Decode time: 0.027 s
- Decode sizes: input 3.818 MB, output 6.261 MB