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An open, educational simulator for payment HSM cryptography and payment network message flows.
Explore how terminals, acquirers, schemes and issuers communicate using AS2805 messages — for card issuance, PIN set, terminal provisioning and purchase transactions.
Explore →Step through individual HSM operations — generate LMKs and zone keys, encrypt PIN blocks, compute MACs, wrap keys with TR-31, and more. All inputs and outputs are visible.
Explore →Explore how money moves through a 4-party card scheme. Follow a transaction from clearing through settlement, and see how interchange fees, scheme fees, and merchant service fees are calculated at each step.
Explore →Paste raw hex bytes from an AS2805.2 message and decode it into human-readable fields, bitmaps, and a colour-coded hex dump.
Explore →The payment scheme simulator needs a screen width of at least 900px to display the network topology, activity records, and key material properly.
Try rotating to landscape, or use a tablet / desktop browser.
Financial Flows needs a screen width of at least 900px to display the settlement network, transaction flows, and account ledgers properly.
Try rotating to landscape, or use a tablet / desktop browser.
Paste the raw hex bytes of an AS2805.2 message (whitespace is ignored). Click Decode to parse it into human-readable fields.
Floor limit — a dollar amount configured per terminal that determines the maximum transaction value eligible for stand-in (offline) approval. If a card-present transaction receives RC=91 (host unreachable) and the amount is at or below the floor limit, the terminal approves offline. Configured during terminal creation in Advanced mode; default $100.00.
Choose an HSM function from the sidebar to get started.