Generate OTP Service

Sets up the device to receive a one-time passcode. A 128-bit nonce, NFPGA, is generated and stored in volatile memory for later use in the rest of the protocol. A 128-bit user nonce, NUSER, is supplied by the user.

This service only unlocks the software debug lock SWL_DEBUG.

Table 1. Generate OTP Service Request
System Service Descriptor Bit Field Value Description
15:7 MBOXADDR[10:2] Mailbox address. See Table 2.
6:0 7AH Generate OTP service command

The following table lists the Generate OTP Service mailbox format.

Table 2. Generate OTP Service Mailbox Format
Offset Length (bytes) Parameter Direction Description
0 1 KEYMODE Input Specifies the key mode used to transport the encrypted passcode. The KEYMODE parameter is not checked for validity until the MATCH OTP service is executed.
4 16 NUSER Input Specifies the user nonce, and is supplied by the user.
20 16 NFPGA Output The 128-bit nonce, NFPGA, is generated and stored in volatile memory for later use in the rest of the protocol.