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← Payment Systems: Magstripe, Tokenization, NFC and EMV
Level 3 · Operator75 min

Contactless limits and the cumulative-limit bypass

Why tapping stops asking for a PIN after five times, where that counter really lives, and two pieces of published research that got past it — one resetting the counter without ever knowing a PIN, one making a plastic card present as a phone to an offline reader anyone can buy.

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What this module covers

  1. 01Three limits, and none of them is the one people mean
  2. 02The comparison is inclusive, and one book says otherwise
  3. 03Nobody assigned these a tag
  4. 04A wall in one country, a gate in another
  5. 05Where the decision is written down
  6. 06Two bits, and a limit that stops applying
  7. 07Why Mastercard was not on that list
  8. 08A kernel that does compare them
  9. 09The counters the card keeps itself
  10. 10Before the rule, there was liability
  11. 11The cumulative limit
  12. 12Three checks, and the gap between them
  13. 13The offline PIN, and the status word that means yes
  14. 14What the card writes down
  15. 15Two schemes, two attack surfaces
  16. 16And then the terminal went offline
  17. 17The fixes, and why they are cheap
  18. 18Four limits, four owners
  19. 19What to test
  20. 20Where to read next
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