Your Fødselsnummer Is Not a Password
·10 mins
The Norwegian national ID number is treated as a secret and structurally cannot be one. A walk through the mod-11 arithmetic, a count of what a birthday actually leaves, and why 2032 is an admission.
Security Notes
Deep dives into specific failure modes: how fraud actually operates, how files lie about what they are, and what the failures say about the systems that trusted them.
2026
2023
Credit Card Security
·15 mins
A defensive guide to how credit-card fraud works in practice: leaked numbers, social media exposure, NFC myths, physical theft, dark-web resale, and realistic protection.
2018
File Spoofing
··8 mins
A practical look at RTLO, shortcuts, misleading extensions, NTFS streams, archives, and polyglots through the thing they all exploit: disagreement about what a file actually is.