Apple Pay生成ARQC时使用的IMK(ac)密钥是哪一个？

Great question—this is a common point of confusion with tokenized EMV transactions like Apple Pay, so let’s break this down clearly:

In Apple Pay EMV transactions where the iPhone generates the ARQC, it does NOT use the original IMK(ac) from the physical card’s chip. Instead, it uses a device-specific variant of IMK(ac) that’s part of the EMV Tokenization Framework’s secure device binding system.

Here’s the key context:

• The physical card’s IMK(ac) is strictly locked to the card’s own Secure Element (SE) and never leaves it—this is a non-negotiable security rule for EMV compliance.
• When you add a card to Apple Pay, your issuing bank completes a tokenization workflow: they generate a unique set of device-bound keys (including a dedicated IMK(ac) equivalent, sometimes called IMK(AP) or IMK(Device)) and securely push this key set into your iPhone’s Secure Enclave.
• This device-specific IMK(ac) is what’s used to derive the session keys needed for ARQC generation during Apple Pay transactions. Just like the physical card’s IMK(ac), only your issuing bank (not card networks like Visa) holds the matching root keys to validate the resulting ARQC.

The core idea here is that Apple Pay’s tokenization creates a fully isolated security domain for the device—separate from the physical card’s domain—with its own exclusive, issuer-managed key set that never touches the original card’s IMK(ac).

内容的提问来源于stack exchange，提问作者Tom West