Writing
Five articles on two themes: what a program should be allowed to reach, and where to put that limit so it cannot be got around; and what it takes to move cryptography and data across the boundaries set by standards, law and networks.
01
Applied cryptography · 2026-09-10 · 6 min read
Swapping the algorithm standard is not a mechanical substitution: curve arithmetic and encodings carried over, ecrecover could only become verification, signing has to stay off-chain, gas had to be re-measured, and the checks at the C boundary decide whether one bad transaction can stop a node.
02
Systems design & tradeoffs · 2026-09-08 · 6 min read
2TB in one night, between two AWS partitions with disconnected IAM systems, over a 150 ms link: why no managed tool applied, how keys get across without a shared symmetric secret, the bandwidth-delay arithmetic, a state machine for resume, and the multipart ETag problem.
03
Design & threat model · 2026-08-14 · 5 min read
An agent read ~/.ssh/id_rsa during a task unrelated to SSH, and the read was entirely within its permissions. Overreach, taking orders and leakage are three different problems, each needing its own layer; enforcement sits at the protocol layer.
04
Detection rules & tradeoffs · 2026-08-14 · 5 min read
An injection detector comes down to three decisions: what to scan, what happens on a hit, and what does the judging. Why a hit blocks the whole result, why the first version uses rules rather than a classifier, and a real hole in the shipped defaults found by the test suite.
05
Privacy design & tradeoffs · 2026-07-31 · 6 min read
Every way data could leave the phone, checked one by one: no network permission and no dependency that could use one, three exits that each require a user action, an optional app lock, and the system backup that 1.6.0 turned off. Evidence for each, and how to verify it on the APK.