⚠ SIMULATOR ONLY — NOT FOR PRODUCTION USE — All keys and values shown in cleartext

Callendina Visible Payments Explorer

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Card Scheme Simulator
HSM Simulator
Financial Flows
AS2805.2 Decoder
Glossary
⚠ This is an educational simulator (beta). All cryptographic keys and data are shown in cleartext. Never use real production keys or cardholder data. Report a bug.

Callendina Visible Payments Explorer

An open, educational simulator for payment HSM cryptography and payment network message flows.

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Card Scheme Simulator

Explore how terminals, acquirers, schemes and issuers communicate using AS2805 messages — for card issuance, PIN set, terminal provisioning and purchase transactions.

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HSM Simulator

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.

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Financial Flows

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.

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AS2805.2 Decoder

Paste raw hex bytes from an AS2805.2 message and decode it into human-readable fields, bitmaps, and a colour-coded hex dump.

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AS2805 • DUKPT • TR-31 • TR-34 • ISO 9797 • RSA — Educational use only
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Larger Screen Required

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.

Test Cards
Network Topology — Simplified AS2805.2 Payments Scheme Key Wrap Compliance View
Presets:
Complete setting up the Scheme, KIF and Perso Bureau, then add an Issuer or Acquirer to get started. Or just press a preset button to have the network built out automatically.
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Larger Screen Required

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.

Cards & Accounts
Financial Flows Current Fees
Presets:
Timeline & Fees

AS2805.2 Message Decoder

Paste the raw hex bytes of an AS2805.2 message (whitespace is ignored). Click Decode to parse it into human-readable fields.

Select a function

Choose an HSM function from the sidebar to get started.

Key Store
Key Wrap Compliance
No saved keys

Save to Key Store

MC.4 — PVV Generate & Verify

Category: MAC / Crypto

Generate or verify a PIN Verification Value using one of three methods. Visa PVV (TDES, 4-digit PINs) — builds a TSP from PIN + PVKI + PAN, encrypts with TDES-ECB, decimalizes to 4 digits. IBM 3624 PIN Offset (TDES, 4-12 digit PINs) — derives a “natural PIN” from the PAN, computes the digit-wise offset between the customer’s PIN and the natural PIN. AES PVV (AES-CMAC, 4-12 digit PINs) — builds an input block from PIN length + PIN + PVKI + PAN, computes AES-CMAC, decimalizes to match PIN length. Use Encrypt PIN Block (PE.1) first to obtain an encrypted PIN block.

← All HSM functions