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DUKPT: a fresh key for every card payment at the counter
The same use case told visually, ready to present. Speaker notes carry the full explanation.
Payments
DUKPT
A fresh key for every card payment at the counter
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today1 / 7
Who holds what
One BDK, any number of devices
200,000 PIN pads, and the host stores exactly one key
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today2 / 7
One transaction
The host re-derives everything from the KSN
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today3 / 7
The counter
One derivation per set bit
A counter with more than 10 one bits (TDES) or 16 (AES) is skipped
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today4 / 7
Lifetime
Counters a device can use before re-injection
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today5 / 7
Migration
From TDES DUKPT to AES DUKPT
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today6 / 7
Limits
What DUKPT doesn't protect against
It protects the past from a compromised device, not the future
DUKPT: a fresh key for every card payment at the counter · Classical Crypto Today7 / 7
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