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4. Introduction

All generations of Nu and ALLS use a USB-based keychip. This keychip is intended to connect to a dedicated port, however can be connected to any USB port.

There are two primary variants of the keychips employing differing security mechanisms. The A7 keychips use the A7001AG JavaCard-based secure smart card processor from NXP, and are marked with a version number of V2.XX. The N2 keychips use an unknown security processor, and are marked with L3.1.

In both variants, a LPC11U14F processor used to handle translation from USB serial to the I2C protocols the A7 and N2 processors use. In addition, 4Mbit of flash is present in the form of a AT25DF041A chip, used to store tracedata and billing information.

Neither games nor the system processes communicate directly with the keychips. Instead, a driver named fdd.sys is used which writes keychip information to the registry, and provides a minimal interface for interacting with the keychip. This driver then dispatches to either hdd.sys (A7) or ssd.sys (N2) to perform the low-level communication with the keychip by means of a dedicated inter-driver communication protocol.