Demystifying the Secure Enclave Processor

Mailbox Message Format
• A single message is 8 bytes in size
• Format depends on the receiving endpoint
• First byte is always the destination endpoint
struct {
uint8_t endpoint; // destination endpoint number
uint8_t tag; // message tag
uint8_t opcode; // message type
uint8_t param; // optional parameter
uint32_t data;
// message data
} sep_msg;