9F2A

Kernel Identifier is the field inside a card's PPSE directory entry that tells Entry Point, the contactless kernel-selection logic, which specific kernel to hand this application off to - the mechanism that makes it possible for one terminal to correctly route a Visa contactless application to Kernel 3, a Mastercard one to Kernel 2, and so on, all from the same directory-reading pass. Byte 1 carries two pieces of information at once: bits 8-7 state the kernel-type encoding (00 for an international kernel identified by a Short Kernel ID alone, 10 or 11 for a domestic kernel that also needs an Extended Kernel ID, 01 reserved), and bits 6-1 carry the Short Kernel ID itself, whose value directly names the kernel: 000010 for Kernel 2 (Mastercard), 000011 for Kernel 3 (Visa), 000100 for Kernel 4 (Amex), 000101 for Kernel 5 (JCB), 000110 for Kernel 6 (Discover), 000111 for Kernel 7 (UnionPay), and 001000 for Kernel 8. It's related to the AID (4F) and Application Priority Indicator (87) as part of the same directory entry, and to its terminal-side counterpart, Kernel Identifier – Terminal (96), which the reader uses to state which kernels it actually supports so Entry Point can match card and terminal capability before selection completes. A terminal that misreads bits 6-1 here routes an application to the wrong kernel entirely - not a subtly wrong transaction, but a completely different processing model applied to data it was never designed to interpret. See EMV Contactless Book B.