Card setup

The settings a user changes on the dongle: PINs, touch policy, key generation and resets. Everything here uses standard tools (gpg, fido2-token) and the standard FIDO2 and OpenPGP card commands. None of it touches the TROPIC01 configuration, its pairing keys, its firmware or the STM32's protection settings.

Set up the host first: Linux setup.

Factory defaults

	Setting	Default
OpenPGP	User PIN (PW1)	123456 — 6 to 64 bytes
	Admin PIN (PW3)	12345678 — 8 to 64 bytes
	Reset Code	not set — 8 to 64 bytes
	Tries per PIN	3
	Keys	none
	Touch (UIF)	on for every key operation
	Signature PIN	not forced: PW1 stays verified until unplug
FIDO2	PIN	not set — 4 to 63 bytes
	Tries	8 in total, at most 3 wrong per plug-in
	alwaysUv	off
	Credentials	none

Change the default OpenPGP PINs first

Anyone who knows the defaults can use a card that still has them.

OpenPGP card

All commands run inside gpg --card-edit, after admin.

PINs

gpg/card> admin
gpg/card> passwd
1 - change PIN            # PW1, used for signing, decryption and SSH
2 - unblock PIN           # new PW1, authorised by the Admin PIN
3 - change Admin PIN      # PW3
4 - set the Reset Code

Do 3, then 1. Set a Reset Code (4) if you want to unblock PW1 without the Admin PIN: the separate unblock command at the gpg/card> prompt (no admin needed) sets a new PW1 with the Reset Code. PIN lengths count bytes, so a non-ASCII character counts more than once.

The PIN retry limit is enforced by the TROPIC01 chip's MAC-and-Destroy function, not by a counter in the firmware: each attempt consumes chip state that only the correct PIN restores. Three wrong PW1 entries block PW1; three wrong PW3 entries block PW3.

Unblocking PW1 destroys the decryption key

The decryption key is stored encrypted under a key derived from PW1 (see security model). Changing PW1 keeps it. Unblocking or resetting PW1 (with the Reset Code or the Admin PIN) cannot recover it, so the card erases it: mail encrypted to that key can no longer be decrypted on this card. Signing and authentication keys are kept. Generate a new encryption key afterwards. This differs from a YubiKey, where the Admin PIN only resets the counter.

Cardholder data

gpg/card> name      # cardholder name
gpg/card> lang      # language preference
gpg/card> salutation

The URL and login data objects are not supported.

Signature PIN (forcesig)

gpg/card> forcesig

Toggles between "PIN once per plug-in" (default) and "PIN for every signature". Decryption and SSH authentication always use the PW1 verification of the current plug-in.

Touch policy (uif)

gpg/card> uif 1 on          # 1 = signature, 2 = decryption, 3 = authentication
gpg/card> uif 1 off
gpg/card> uif 1 permanent

The card has one touch flag for all three keys: setting it through any key sets it for all. When on, every signature, decryption and SSH authentication waits up to 15 s for a press of SW1 (the LED blinks). permanent cannot be switched off again; only a factory reset clears it.

Needs v0.3.2 or later: older firmware did not announce the button, and gpg refused uif as not supported.

Generate keys

gpg/card> generate
Make off-card backup of encryption key? (Y/n) n

gpg asks for PW1, then the Admin PIN. Answer n to the backup question: the card generates the keys itself and offers no backup. The algorithms are fixed:

Key	Algorithm	Where it lives
Signature	Ed25519	TROPIC01 key slot, never leaves the chip
Decryption	Curve25519 (X25519)	generated on the STM32, stored sealed under PW1
Authentication	Ed25519	TROPIC01 key slot, never leaves the chip

Importing keys made elsewhere (keytocard) is not supported; see the roadmap.

Factory reset

gpg/card> factory-reset

Erases all keys, PINs and cardholder data and restores the defaults. It needs no PIN: gpg first blocks PW1 and the Admin PIN with wrong attempts, then terminates and re-activates the card. This is the way back when the Admin PIN is forgotten.

FIDO2

Find the device path first:

fido2-token -L
# /dev/hidraw5: vendor=0xcafe, product=0x4001 (nixtropic nixtropic)

Task	Command
Set a PIN	fido2-token -S /dev/hidrawN
Change the PIN	fido2-token -C /dev/hidrawN
alwaysUv on / off	fido2-token -S -u /dev/hidrawN / fido2-token -D -u /dev/hidrawN
Show device info	fido2-token -I /dev/hidrawN
List discoverable credentials	fido2-token -L -r /dev/hidrawN
Delete a credential	fido2-token -D -i <credential-id> /dev/hidrawN

Setting the first PIN also switches alwaysUv on, so every login then asks for the PIN. Switch it off with fido2-token -D -u if you want sites to decide. Every registration and login waits for a press of SW1.

After 8 wrong PINs in total the PIN is blocked and only a reset helps. After 3 wrong PINs in one plug-in, unplug and replug to continue.

FIDO reset

A reset erases every FIDO credential and the PIN. It works only within 10 seconds of plugging in, and it always asks for a press of SW1:

fido2-token -R /dev/hidrawN      # replug first, then run within 10 s; press SW1 when the LED blinks

The window and the press stop software on the computer from wiping the dongle at an arbitrary moment. They do not stop someone who holds the dongle: replugging opens the window again.

What the card does not do

Not supported	Why
RSA keys	TROPIC01 has no RSA; ECC only
Key import (keytocard)	not implemented yet
Per-key touch policy, cached touch	one global flag today (backlog)
KDF-DO, URL and login DOs, private DOs	not implemented
FIDO hmac-secret, credProtect, PIN protocol 2	not implemented; GetInfo reports FIDO_2_0 honestly
FIDO attestation	none format; the AAGUID is self-assigned (WebAuthn notes)