Steganodf

Steganodf hides a secret message inside a dataframe.

Give it a dataframe and a few bytes to hide, steganodf gives you back a dataframe that still looks and reads like the original but carries your secret message. Anyone with the password (or with none, if you did not set one) can read the message back out. Typical use: watermarking a dataset you are about to share, so that a leaked copy can be traced back to the recipient it was issued to.

Hiding data in a table is a trade-off between three properties, and no single scheme wins on all three at once:

• Capacity — how many bytes fit in the dataset.
• Robustness — does the message survive what happens to data
• Invisibility — how much the original data is distorted, and how easily an observer can tell that a watermark is there at all.

Steganodf ships four algorithms that sit at different points of that trade-off.

Usage

Try it in your browser

The web app runs the whole library in your browser, compiled to WebAssembly: nothing is uploaded, the dataframe never leaves your machine — https://dridk.github.io/steganodf/

From the command line

With uv, uvx steganodf ... runs the command line in a throwaway environment, without installing anything. Otherwise install it the usual way:

pip install steganodf

steganodf --version

# Encoding
steganodf encode -m hello host.csv stegano.csv
steganodf encode -m hello host.parquet stegano.parquet
steganodf encode -m hello -p password host.parquet stegano.parquet

# Decoding
steganodf decode stegano.csv
steganodf decode stegano.csv -p password

# Choosing an algorithm, and the carrier column for bitvote / bitghost
steganodf encode -m hello -a bitvote -c price host.csv stegano.csv
steganodf decode -a bitvote -c price stegano.csv

# Decoding without knowing the algorithm: tries all four, names the one that matched
steganodf decode -a auto stegano.csv

The CLI reads and writes .csv and .parquet, and exposes --password, --column and --algorithm. Tuning parameters such as bit_per_row or data_size are Python-only.

From Python

import steganodf
import polars as pl

df = pl.read_parquet("my_dataset.parquet")

# The payload is bytes, not str
watermarked = steganodf.encode(df, b"made by steganodf", password="secret")

# Extract your message from the watermarked dataframe
message = steganodf.decode(watermarked, password="secret")

decode returns empty bytes when no complete message could be recovered, so "no watermark here" and "the watermark says nothing" look alike; decode_details and try_decode (below) both report a success flag instead.

Pass algorithm= to encode and decode. Both sides must agree on the algorithm and on every parameter that affects the framing (password, bit_per_row, data_size, sort_columns…).

# A shuffle-resistant watermark
watermarked = steganodf.encode(df, b"made by steganodf", algorithm="bitvote")
shuffled = watermarked.sample(fraction=1.0, shuffle=True)

steganodf.decode(shuffled, algorithm="bitvote")   # b'made by steganodf'

For anything beyond the defaults, instantiate the class directly:

from steganodf.algorithms import BitPool, BitSync, BitVote, BitGhost

# 8 bits per row instead of 1: ~7x the capacity on a large dataframe
algorithm = BitPool(bit_per_row=8, password="secret")
algorithm.get_max_payload_size(df)          # conservative estimate, in bytes
watermarked = algorithm.encode(df, b"a much longer message ...")

If you receive a watermarked dataframe without being told which algorithm wrote it, pass algorithm="auto". Every algorithm validates what it reads with a CRC32, so one that was not used to encode reports a failure rather than returning garbage; steganodf tries them in turn and stops at the first success.

steganodf.decode(df, algorithm="auto", password="secret")   # b'made by steganodf'

try_decode does the same thing but also tells you which algorithm matched:

steganodf.try_decode(df, password="secret")
# {'payload': b'made by steganodf', 'success': True, 'votes': 100000,
#  'margin_min': 469, 'algorithm': 'bitvote', 'tried': ['bitvote']}

Only the default parameters are tried. bit_per_row, data_size and redundancy must match between encoding and decoding and cannot be guessed, so a dataframe watermarked with BitPool(bit_per_row=8) will not be found by auto decoding — but everything the command line produces will, since it always uses the defaults. The password is not guessed either.

The candidates are tried cheapest first (bitvote, bitghost, bitpool, bitsync), so the slow ones only run once the fast ones have failed.

Algorithms in detail

The three methods:

• permutation — the message lives in the order of the rows. Nothing is written to the data itself, so the dataset is bit-for-bit the same multiset of rows. The price is that any operation that re-orders the table erases the message.
• alteration — the message lives in the least significant bits of one numeric column. The values change, by one unit in the last place, and the row order becomes irrelevant.
• synthesis — the message lives in extra rows that steganodf fabricates and inserts. Existing values are never touched, but the dataset gains records that were not in it.

DETAIL.md covers each algorithm in turn — what it is built on, what it is good at, where it breaks — plus the threat model.

Benchmark

Measured on a 100 000-row, 4-column frame (Int64, Utf8, two Float64) with a 16-byte payload.

Development and releases

steganodf requires Python 3.11+ and is developed with uv:

uv sync --extra dev
uv run pytest --doctest-modules steganodf tests   # or: make test

Every push and pull request on main and dev runs the test suite on Python 3.11 and 3.13 (.github/workflows/tests.yml).

Releasing to PyPI is automated (.github/workflows/publish.yml, trusted publishing over OIDC — no API token). To cut a release:

1. On dev: bump version in pyproject.toml, run uv lock, commit.
2. Merge dev into main and push.
3. git tag 0.3.0 && git push origin 0.3.0

The tag triggers the tests, then a build whose version must match pyproject.toml (the workflow fails otherwise), then the upload to PyPI. make publish prints this checklist with the current version.

Citation

Sacha Schutz, Meganne Souprayen. Watermark tabular datasets with rows permutations and fountain code. TechRxiv. April 28, 2025. DOI: 10.36227/techrxiv.174585796.61215338/v1

@article{schutz2025steganodf,
  title   = {Watermark tabular datasets with rows permutations and fountain code},
  author  = {Schutz, Sacha and Souprayen, Meganne},
  year    = {2025},
  month   = {4},
  journal = {TechRxiv},
  doi     = {10.36227/techrxiv.174585796.61215338/v1},
  url     = {https://www.techrxiv.org/doi/full/10.36227/techrxiv.174585796.61215338/v1}
}