The task behind the project
belegwerk treats an invoice as structured data. JSON becomes a PDF; a register records entries linked by SHA-256 hashes. I contribute product work and development. The code is public under MIT.
The idea is a manageable tool with readable files that can be backed up and processed further. Users remain responsible for correct information, retention and their particular use. This is not a guarantee of legal compliance.
Hash chains need careful explanation. Changing entries usually changes subsequent hashes. But someone able to rewrite the whole register and replace every hash can create another internally consistent chain. A reliable comparison therefore needs an independently preserved, trusted version.
This project illustrates theory meeting practice: a hash’s mathematical properties are useful, but do not answer every operational question about invoicing. The accompanying guide introduces SHA-256 through verifiable examples.
Key facts
- My role
- Product and development
- Formats
- JSON, PDF and a chained register
- Source code
- Public · MIT licence
- Description as of
- 18.09.2026
Project & further sources
Thinking beyond the work
Hashing, encryption and digital signatures: the difference
Checksums, confidentiality and verifiable origin serve different purposes. A decision guide for files, backups and software protocols.
Checking files with PowerShell: SHA-256 and the right bytes
A reproducible PowerShell exercise: create a test file, calculate SHA-256, compare line endings and interpret results correctly. With a PDF edition.
Understanding SHA-256: from bytes to a hash
Why a SHA-256 hash has 64 hexadecimal characters, how bytes matter and what a checksum actually establishes. With examples, a browser demo and PDF.
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