Defensive Architecture: YellowKey: TPM Interception Logic

The YellowKey exploit functions by hooking the BIOS/UEFI interrupts during the pre-boot phase. It specifically targets PCR (Platform Configuration Register) 7, which stores the 'Secure Boot' state. By capturing the buffer during the TPM handshake, the attacker can reconstruct the Bitlocker Volume Master Key (VMK) without needing the user's PIN.

function intercept_tpm_handshake() {
  if (boot_stage == 'PRE_KERNEL') {
    hook_interrupt(0x13); // Hook Disk I/O
    capture_buffer(TPM_PCR_REGISTER_7);
    send_to_attacker_vhd(capture_buffer);
  }
}

The most effective defense is the use of 'TPM + PIN' or 'TPM + Startup Key' authentication. This ensures that even if the TPM handshake is intercepted, the attacker lacks the second factor required to derive the final decryption key.