Can you find the root cause of three real-world payment failures from the logs?

2026-08-01  MTI 0110  DE39=00  approved      StreamCo monthly plan, card on file
2026-08-14  (issuer reissues the card with a new expiry date)
2026-09-01  MTI 0100  merchant-initiated, card on file, amount 12.99
            DE2  4000 •••• •••• 1234   DE14 2608 (stored expiry)
2026-09-01  MTI 0110  DE39=54

All puzzles and what they teach

1. Route the payment

   Chip at the counterWarm-up

   Can you get a chip payment from the counter to the card’s bank?

   PlayRead: ISO 8583 Protocol

2. Route the payment

   Verify the chipMedium

   Can you deliver a chip’s cryptogram to the only system able to check it?

   PlayRead: NFC in Payments

3. Route the payment

   Tap with a phoneMedium

   Can you get a phone tap approved by a bank that has never seen the phone’s card number?

   PlayRead: Payment Tokenization

4. Route the payment

   Online PINHard

   Can you get an encrypted PIN to the issuer without anyone reading it on the way?

   PlayRead: TR-31 & TR-34 Key Standards

5. Route the payment

   Checkout with 3-D SecureExpert

   Can you authenticate and authorize an online payment in the right order?

   PlayRead: 3D Secure (EMV 3DS)

6. Put it in order

   Chip transaction, step by stepMedium

   Can you put the steps of a chip payment in the order the card and terminal run them?

   PlayRead: EMV Contactless Kernels 2–8

7. Set the bits

   Read the TVRMedium

   Can you set the TVR bits that record what the terminal found?

   PlayRead: EMV Contactless Kernels 2–8

8. Diagnose

   Diagnose the declineHard

   Can you find the root cause of three real-world payment failures from the logs?

   PlayRead: ISO 8583 Protocol