py-self-md5

py-self-md5 wraps a Python script so the generated script prints MD5: <DIGEST> before running the original program.

The generated script does not read its own source file at runtime. Instead, the inserted prefix stores a quine-style byte template and computes the digest from the reconstructed bytes in memory.

This project is inspired by zhuzilin/pdf-with-its-own-md5, where selectable MD5-collision carriers are used to display the final digest in a PDF. This tool targets executable Python programs and does not require HashClash or precomputed collision blocks.

Install

Requires Python 3.11 or newer.

python -m pip install py-self-md5

After installation, run the built-in check:

py-self-md5 --self-test

You can also run it from the project root without installing:

python -m py_self_md5 --self-test

Usage

Create input.self_md5.py:

py-self-md5 input.py

Run the generated script:

python input.self_md5.py

The first output line is MD5: <DIGEST>, where <DIGEST> is the uppercase MD5 digest of input.self_md5.py; then the original program continues.

Write to a specific path:

py-self-md5 input.py -o output.py

Rewrite the input file in place:

py-self-md5 input.py --in-place

Replace an existing py-self-md5 prefix in place:

py-self-md5 input.py --in-place --force

Overwrite an existing output file:

py-self-md5 input.py -o output.py --force

Generate and verify in one step:

py-self-md5 input.py --check

What the wrapper preserves

• The tool preserves shebang lines, encoding cookies, module docstrings, and from __future__ import ... placement.
• By default, the input file is not modified.
• Existing py-self-md5 prefixes are detected. Use --force to replace one.

Limitations

• This is an executable self-hash wrapper, not a general MD5 collision generator.
• The generated prefix can be large because it embeds enough bytes to reconstruct the generated script in memory.
• --check executes the generated script, so only use it with programs you are willing to run.