Question 1

What is DUKPT?

Accepted Answer

DUKPT (Derived Unique Key Per Transaction) is a key management scheme that derives a unique encryption key for each transaction from a Base Derivation Key (BDK) and Key Serial Number (KSN). It is widely used in POS terminals and ATM systems.

Question 2

What is the difference between BDK and IPEK?

Accepted Answer

BDK (Base Derivation Key) is the master key held by the key injection facility. IPEK (Initial PIN Encryption Key) is the first derived key injected into the device. IPEK is derived from BDK and the device's KSN base.

Question 3

What is KSN?

Accepted Answer

KSN (Key Serial Number) is a 10-byte value that uniquely identifies each transaction. It contains the device serial number and a transaction counter. Each KSN produces a unique derived key.

Question 4

Why is DUKPT considered secure?

Accepted Answer

DUKPT is secure because each transaction uses a different encryption key. If a key is compromised, it cannot be used to decrypt past transactions (forward secrecy). Only future transactions using that specific device would be at risk.

Question 5

What is Data Variant in DUKPT?

Accepted Answer

Data Variant is a key modification technique where the encryption key is XORed with a fixed pattern (typically 0x000...0FF) before use. This creates different keys for different purposes (PIN, MAC, Data) from the same derived key.

DUKPT (ISO 9797)

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DUKPT FAQ