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Writing
Notes on payment systems, device software, transaction uncertainty, platform design, and the emerging role of AI in commerce. I write from the questions that appear in real operating conditions.
Terminal key rotation is the operation most fleets avoid until they can't. A design for making it routine rather than dramatic.
PCI-DSS v4.0 is now mandatory. Beyond the well-publicised customized approach, several less-discussed changes shift how integrations should be built.
A key ceremony is a scripted piece of theatre with real cryptographic consequences. The failure modes are entirely operational.
A token vault is a small service with an outsized responsibility. Common design mistakes and what to do instead.
EMV 3DS 2.3 moves several decisions from the issuer to the ACS, and from the ACS to real-time context. What that means for merchants.
TLS 1.3 became mandatory in most compliance frameworks by 2025. Deploying it across a device fleet has some rougher edges than the browser story suggested.
Pinning is a defense against a specific attack. On an Android POS fleet, the wrong pinning strategy is the operational problem that never leaves.
The insider threat model is different from the external one. Where the discipline usually breaks down.
Passing an audit is not the same as being secure. Where the gap is widest, and how to close it.
Terminals that operate offline for periods need a key-exchange design that doesn't assume connectivity at all the right moments.