🔐Duress PIN

Use the IODD Duress PIN, also known as a decoy PIN, to show only a prepared vhd4.vhd volume for plausibly deniable access.

The Duress PIN feature, also called a decoy PIN, lets an IODD ST400 or MINI PRO present only a prepared vhd4.vhd virtual disk to the PC when the device is unlocked with the User 4 PIN.

This mode is useful when you need to expose a separate, shareable volume while keeping the normal storage area separate from the PC session. It can support a plausibly deniable access workflow by showing a prepared decoy volume instead of the normal physical partition.

Supported Models and Firmware Duress PIN with vhd4.vhd is supported on ST400 and MINI PRO with firmware version 82 or later, updated using iodd_firm_upd-0.8.2.0_xx.exe or later.

---

Terminology: Duress PIN, Decoy PIN, and Plausibly Deniable Access

In this guide, Duress PIN refers to the IODD feature name. Decoy PIN is a common search term for a PIN that opens a prepared alternate volume. Plausibly deniable access describes the user-facing result: the PC sees only the prepared vhd4.vhd disk during that session.

---

How It Works

When the device is unlocked with a PIN other than User 4, the PC sees the normal physical partition. Use this state to create, delete, or update vhd4.vhd.

When the device is unlocked with the User 4 PIN, the PC sees only the disk mapped to vhd4.vhd. Other files from the physical partition are not shown in that session.

Unlock Method	Main Purpose	What the PC Sees
PIN other than User 4	File management, ISO/VHD management, vhd4.vhd setting update	Normal physical partition
User 4 PIN	Duress PIN access	Disk sized to vhd4.vhd

---

Preparing vhd4.vhd

1. Unlock the device with a PIN other than the User 4 PIN.

2. On the PC, create a file named exactly vhd4.vhd in the root folder of the first partition.

3. Make sure the file is in the root folder, not in a subfolder.

4. Return to the root folder list on the device screen.

5. Rebuild the root folder list by pressing Key 1, rebooting the device, or entering a subfolder and returning to the root folder.

6. When vhd4.vhd appears in the list, the device updates the VHD setting.

7. Unlock the device again with the User 4 PIN.

8. The PC shows a disk whose size matches vhd4.vhd.

When creating vhd4.vhd, use VHD_Tool++ v0.9.0.10 or later from the IODD Download Center. VHD_Tool++ is a Windows-only tool.

---

vhd4.vhd Requirements

Item	Requirement
File name	vhd4.vhd
Location	Root folder of the first partition
Format	Fixed-size VHD file
Unsupported formats	Dynamic VHD, VHDX
Placement	Contiguous, without fragmentation

Select vhd4.vhd on the device and press Key 5 to display the file information message. The fragment value must be 1.

A fragmented vhd4.vhd cannot be used. If the LCD shows a defragmentation or DEFRAG message, recreate vhd4.vhd as a contiguous fixed-size VHD file, then unlock with a PIN other than User 4 and rebuild the root folder list.

---

Updating the VHD Setting

The device checks whether vhd4.vhd exists when it builds the root folder list.

State	Device Behavior
vhd4.vhd exists and is not fragmented	Updates the VHD setting for use with the User 4 PIN
vhd4.vhd exists but is fragmented	Does not apply the VHD setting
vhd4.vhd does not exist	Deletes the saved VHD setting

Rebuild the root folder list only while unlocked with a PIN other than the User 4 PIN. A user with disk write protection cannot update the vhd4.vhd setting.

---

Troubleshooting

The VHD Disk Does Not Appear After Unlocking With the User 4 PIN

1. Unlock the device with a PIN other than the User 4 PIN.

2. Check that vhd4.vhd exists in the root folder of the first partition.

3. Rebuild the root folder list by pressing Key 1, rebooting the device, or entering a subfolder and returning to the root folder.

4. Check that vhd4.vhd is not fragmented.

5. Unlock again with the User 4 PIN.

If the PIN used to update the setting has disk write protection enabled, the VHD setting cannot be updated.

The Device Does Not Recognize vhd4.vhd

• Make sure the file name is exactly vhd4.vhd.

• Make sure the file is in the root folder of the first partition.

• Make sure the root folder list was rebuilt after creating the file.

• Make sure the file is a fixed-size VHD, not a dynamic VHD or VHDX file.

• Make sure the file is not fragmented.

A Defragmentation or DEFRAG Message Appears

vhd4.vhd is not stored contiguously on the disk. Delete and recreate vhd4.vhd on the PC, or arrange it so it is stored in a contiguous area. Then unlock with a PIN other than the User 4 PIN and rebuild the root folder list.