OpenPGP master key on Nitrokey Start

I’ve used hardware-backed OpenPGP keys since 2006 when I imported newly generated rsa1024 subkeys to a FSFE Fellowship card. This worked well for several years, and I recall buying more ZeitControl cards for multi-machine usage and backup purposes. As a side note, I recall being unsatisfied with the weak 1024-bit RSA subkeys at the time – my primary key was a somewhat stronger 1280-bit RSA key created back in 2002 — but OpenPGP cards at the time didn’t support more than 1024 bit RSA, and were (and still often are) also limited to power-of-two RSA key sizes which I dislike.

I had my master key on disk with a strong password for a while, mostly to refresh expiration time of the subkeys and to sign other’s OpenPGP keys. At some point I stopped carrying around encrypted copies of my master key. That was my main setup when I migrated to a new stronger RSA 3744 bit key with rsa2048 subkeys on a YubiKey NEO back in 2014. At that point, signing other’s OpenPGP keys was a rare enough occurrence that I settled with bringing out my offline machine to perform this operation, transferring the public key to sign on USB sticks. In 2019 I re-evaluated my OpenPGP setup and ended up creating a offline Ed25519 key with subkeys on a FST-01G running Gnuk. My approach for signing other’s OpenPGP keys were still to bring out my offline machine and sign things using the master secret using USB sticks for storage and transport. Which meant I almost never did that, because it took too much effort. So my 2019-era Ed25519 key still only has a handful of signatures on it, since I had essentially stopped signing other’s keys which is the traditional way of getting signatures in return.

None of this caused any critical problem for me because I continued to use my old 2014-era RSA3744 key in parallel with my new 2019-era Ed25519 key, since too many systems didn’t handle Ed25519. However, during 2022 this changed, and the only remaining environment that I still used my RSA3744 key for was in Debian — and they require OpenPGP signatures on the new key to allow it to replace an older key. I was in denial about this sub-optimal solution during 2022 and endured its practical consequences, having to use the YubiKey NEO (which I had replaced with a permanently inserted YubiKey Nano at some point) for Debian-related purposes alone.

In December 2022 I bought a new laptop and setup a FST-01SZ with my Ed25519 key, and while I have taken a vacation from Debian, I continue to extend the expiration period on the old RSA3744-key in case I will ever have to use it again, so the overall OpenPGP setup was still sub-optimal. Having two valid OpenPGP keys at the same time causes people to use both for email encryption (leading me to have to use both devices), and the WKD Key Discovery protocol doesn’t like two valid keys either. At FOSDEM’23 I ran into Andre Heinecke at GnuPG and I couldn’t help complain about how complex and unsatisfying all OpenPGP-related matters were, and he mildly ignored my rant and asked why I didn’t put the master key on another smartcard. The comment sunk in when I came home, and recently I connected all the dots and this post is a summary of what I did to move my offline OpenPGP master key to a Nitrokey Start.

First a word about device choice, I still prefer to use hardware devices that are as compatible with free software as possible, but the FST-01G or FST-01SZ are no longer easily available for purchase. I got a comment about Nitrokey start in my last post, and had two of them available to experiment with. There are things to dislike with the Nitrokey Start compared to the YubiKey (e.g., relative insecure chip architecture, the bulkier form factor and lack of FIDO/U2F/OATH support) but – as far as I know – there is no more widely available owner-controlled device that is manufactured for an intended purpose of implementing an OpenPGP card. Thus it hits the sweet spot for me.

Nitrokey Start

The first step is to run latest firmware on the Nitrokey Start – for bug-fixes and important OpenSSH 9.0 compatibility – and there are reproducible-built firmware published that you can install using pynitrokey. I run Trisquel 11 aramo on my laptop, which does not include the Python Pip package (likely because it promotes installing non-free software) so that was a slight complication. Building the firmware locally may have worked, and I would like to do that eventually to confirm the published firmware, however to save time I settled with installing the Ubuntu 22.04 packages on my machine:

$ sha256sum python3-pip*
ded6b3867a4a4cbaff0940cab366975d6aeecc76b9f2d2efa3deceb062668b1c  python3-pip_22.0.2+dfsg-1ubuntu0.2_all.deb
e1561575130c41dc3309023a345de337e84b4b04c21c74db57f599e267114325  python3-pip-whl_22.0.2+dfsg-1ubuntu0.2_all.deb
$ doas dpkg -i python3-pip*
...
$ doas apt install -f
...
$

Installing pynitrokey downloaded a bunch of dependencies, and it would be nice to audit the license and security vulnerabilities for each of them. (Verbose output below slightly redacted.)

jas@kaka:~$ pip3 install --user pynitrokey
Collecting pynitrokey
  Downloading pynitrokey-0.4.34-py3-none-any.whl (572 kB)
Collecting frozendict~=2.3.4
  Downloading frozendict-2.3.5-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (113 kB)
Requirement already satisfied: click<9,>=8.0.0 in /usr/lib/python3/dist-packages (from pynitrokey) (8.0.3)
Collecting ecdsa
  Downloading ecdsa-0.18.0-py2.py3-none-any.whl (142 kB)
Collecting python-dateutil~=2.7.0
  Downloading python_dateutil-2.7.5-py2.py3-none-any.whl (225 kB)
Collecting fido2<2,>=1.1.0
  Downloading fido2-1.1.0-py3-none-any.whl (201 kB)
Collecting tlv8
  Downloading tlv8-0.10.0.tar.gz (16 kB)
  Preparing metadata (setup.py) ... done
Requirement already satisfied: certifi>=14.5.14 in /usr/lib/python3/dist-packages (from pynitrokey) (2020.6.20)
Requirement already satisfied: pyusb in /usr/lib/python3/dist-packages (from pynitrokey) (1.2.1.post1)
Collecting urllib3~=1.26.7
  Downloading urllib3-1.26.15-py2.py3-none-any.whl (140 kB)
Collecting spsdk<1.8.0,>=1.7.0
  Downloading spsdk-1.7.1-py3-none-any.whl (684 kB)
Collecting typing_extensions~=4.3.0
  Downloading typing_extensions-4.3.0-py3-none-any.whl (25 kB)
Requirement already satisfied: cryptography<37,>=3.4.4 in /usr/lib/python3/dist-packages (from pynitrokey) (3.4.8)
Collecting intelhex
  Downloading intelhex-2.3.0-py2.py3-none-any.whl (50 kB)
Collecting nkdfu
  Downloading nkdfu-0.2-py3-none-any.whl (16 kB)
Requirement already satisfied: requests in /usr/lib/python3/dist-packages (from pynitrokey) (2.25.1)
Collecting tqdm
  Downloading tqdm-4.65.0-py3-none-any.whl (77 kB)
Collecting nrfutil<7,>=6.1.4
  Downloading nrfutil-6.1.7.tar.gz (845 kB)
  Preparing metadata (setup.py) ... done
Requirement already satisfied: cffi in /usr/lib/python3/dist-packages (from pynitrokey) (1.15.0)
Collecting crcmod
  Downloading crcmod-1.7.tar.gz (89 kB)
  Preparing metadata (setup.py) ... done
Collecting libusb1==1.9.3
  Downloading libusb1-1.9.3-py3-none-any.whl (60 kB)
Collecting pc_ble_driver_py>=0.16.4
  Downloading pc_ble_driver_py-0.17.0-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (2.9 MB)
Collecting piccata
  Downloading piccata-2.0.3-py3-none-any.whl (21 kB)
Collecting protobuf<4.0.0,>=3.17.3
  Downloading protobuf-3.20.3-cp310-cp310-manylinux_2_12_x86_64.manylinux2010_x86_64.whl (1.1 MB)
Collecting pyserial
  Downloading pyserial-3.5-py2.py3-none-any.whl (90 kB)
Collecting pyspinel>=1.0.0a3
  Downloading pyspinel-1.0.3.tar.gz (58 kB)
  Preparing metadata (setup.py) ... done
Requirement already satisfied: pyyaml in /usr/lib/python3/dist-packages (from nrfutil<7,>=6.1.4->pynitrokey) (5.4.1)
Requirement already satisfied: six>=1.5 in /usr/lib/python3/dist-packages (from python-dateutil~=2.7.0->pynitrokey) (1.16.0)
Collecting pylink-square<0.11.9,>=0.8.2
  Downloading pylink_square-0.11.1-py2.py3-none-any.whl (78 kB)
Collecting jinja2<3.1,>=2.11
  Downloading Jinja2-3.0.3-py3-none-any.whl (133 kB)
Collecting bincopy<17.11,>=17.10.2
  Downloading bincopy-17.10.3-py3-none-any.whl (17 kB)
Collecting fastjsonschema>=2.15.1
  Downloading fastjsonschema-2.16.3-py3-none-any.whl (23 kB)
Collecting astunparse<2,>=1.6
  Downloading astunparse-1.6.3-py2.py3-none-any.whl (12 kB)
Collecting oscrypto~=1.2
  Downloading oscrypto-1.3.0-py2.py3-none-any.whl (194 kB)
Collecting deepmerge==0.3.0
  Downloading deepmerge-0.3.0-py2.py3-none-any.whl (7.6 kB)
Collecting pyocd<=0.31.0,>=0.28.3
  Downloading pyocd-0.31.0-py3-none-any.whl (12.5 MB)
Collecting click-option-group<0.6,>=0.3.0
  Downloading click_option_group-0.5.5-py3-none-any.whl (12 kB)
Collecting pycryptodome<4,>=3.9.3
  Downloading pycryptodome-3.17-cp35-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (2.1 MB)
Collecting pyocd-pemicro<1.2.0,>=1.1.1
  Downloading pyocd_pemicro-1.1.5-py3-none-any.whl (9.0 kB)
Requirement already satisfied: colorama<1,>=0.4.4 in /usr/lib/python3/dist-packages (from spsdk<1.8.0,>=1.7.0->pynitrokey) (0.4.4)
Collecting commentjson<1,>=0.9
  Downloading commentjson-0.9.0.tar.gz (8.7 kB)
  Preparing metadata (setup.py) ... done
Requirement already satisfied: asn1crypto<2,>=1.2 in /usr/lib/python3/dist-packages (from spsdk<1.8.0,>=1.7.0->pynitrokey) (1.4.0)
Collecting pypemicro<0.2.0,>=0.1.9
  Downloading pypemicro-0.1.11-py3-none-any.whl (5.7 MB)
Collecting libusbsio>=2.1.11
  Downloading libusbsio-2.1.11-py3-none-any.whl (247 kB)
Collecting sly==0.4
  Downloading sly-0.4.tar.gz (60 kB)
  Preparing metadata (setup.py) ... done
Collecting ruamel.yaml<0.18.0,>=0.17
  Downloading ruamel.yaml-0.17.21-py3-none-any.whl (109 kB)
Collecting cmsis-pack-manager<0.3.0
  Downloading cmsis_pack_manager-0.2.10-py2.py3-none-manylinux1_x86_64.whl (25.1 MB)
Collecting click-command-tree==1.1.0
  Downloading click_command_tree-1.1.0-py3-none-any.whl (3.6 kB)
Requirement already satisfied: bitstring<3.2,>=3.1 in /usr/lib/python3/dist-packages (from spsdk<1.8.0,>=1.7.0->pynitrokey) (3.1.7)
Collecting hexdump~=3.3
  Downloading hexdump-3.3.zip (12 kB)
  Preparing metadata (setup.py) ... done
Collecting fire
  Downloading fire-0.5.0.tar.gz (88 kB)
  Preparing metadata (setup.py) ... done
Requirement already satisfied: wheel<1.0,>=0.23.0 in /usr/lib/python3/dist-packages (from astunparse<2,>=1.6->spsdk<1.8.0,>=1.7.0->pynitrokey) (0.37.1)
Collecting humanfriendly
  Downloading humanfriendly-10.0-py2.py3-none-any.whl (86 kB)
Collecting argparse-addons>=0.4.0
  Downloading argparse_addons-0.12.0-py3-none-any.whl (3.3 kB)
Collecting pyelftools
  Downloading pyelftools-0.29-py2.py3-none-any.whl (174 kB)
Collecting milksnake>=0.1.2
  Downloading milksnake-0.1.5-py2.py3-none-any.whl (9.6 kB)
Requirement already satisfied: appdirs>=1.4 in /usr/lib/python3/dist-packages (from cmsis-pack-manager<0.3.0->spsdk<1.8.0,>=1.7.0->pynitrokey) (1.4.4)
Collecting lark-parser<0.8.0,>=0.7.1
  Downloading lark-parser-0.7.8.tar.gz (276 kB)
  Preparing metadata (setup.py) ... done
Requirement already satisfied: MarkupSafe>=2.0 in /usr/lib/python3/dist-packages (from jinja2<3.1,>=2.11->spsdk<1.8.0,>=1.7.0->pynitrokey) (2.0.1)
Collecting asn1crypto<2,>=1.2
  Downloading asn1crypto-1.5.1-py2.py3-none-any.whl (105 kB)
Collecting wrapt
  Downloading wrapt-1.15.0-cp310-cp310-manylinux_2_5_x86_64.manylinux1_x86_64.manylinux_2_17_x86_64.manylinux2014_x86_64.whl (78 kB)
Collecting future
  Downloading future-0.18.3.tar.gz (840 kB)
  Preparing metadata (setup.py) ... done
Collecting psutil>=5.2.2
  Downloading psutil-5.9.4-cp36-abi3-manylinux_2_12_x86_64.manylinux2010_x86_64.manylinux_2_17_x86_64.manylinux2014_x86_64.whl (280 kB)
Collecting capstone<5.0,>=4.0
  Downloading capstone-4.0.2-py2.py3-none-manylinux1_x86_64.whl (2.1 MB)
Collecting naturalsort<2.0,>=1.5
  Downloading naturalsort-1.5.1.tar.gz (7.4 kB)
  Preparing metadata (setup.py) ... done
Collecting prettytable<3.0,>=2.0
  Downloading prettytable-2.5.0-py3-none-any.whl (24 kB)
Collecting intervaltree<4.0,>=3.0.2
  Downloading intervaltree-3.1.0.tar.gz (32 kB)
  Preparing metadata (setup.py) ... done
Collecting ruamel.yaml.clib>=0.2.6
  Downloading ruamel.yaml.clib-0.2.7-cp310-cp310-manylinux_2_17_x86_64.manylinux2014_x86_64.manylinux_2_24_x86_64.whl (485 kB)
Collecting termcolor
  Downloading termcolor-2.2.0-py3-none-any.whl (6.6 kB)
Collecting sortedcontainers<3.0,>=2.0
  Downloading sortedcontainers-2.4.0-py2.py3-none-any.whl (29 kB)
Requirement already satisfied: wcwidth in /usr/lib/python3/dist-packages (from prettytable<3.0,>=2.0->pyocd<=0.31.0,>=0.28.3->spsdk<1.8.0,>=1.7.0->pynitrokey) (0.2.5)
Building wheels for collected packages: nrfutil, crcmod, sly, tlv8, commentjson, hexdump, pyspinel, fire, intervaltree, lark-parser, naturalsort, future
  Building wheel for nrfutil (setup.py) ... done
  Created wheel for nrfutil: filename=nrfutil-6.1.7-py3-none-any.whl size=898520 sha256=de6f8803f51d6c26d24dc7df6292064a468ff3f389d73370433fde5582b84a10
  Stored in directory: /home/jas/.cache/pip/wheels/39/2b/9b/98ab2dd716da746290e6728bdb557b14c1c9a54cb9ed86e13b
  Building wheel for crcmod (setup.py) ... done
  Created wheel for crcmod: filename=crcmod-1.7-cp310-cp310-linux_x86_64.whl size=31422 sha256=5149ac56fcbfa0606760eef5220fcedc66be560adf68cf38c604af3ad0e4a8b0
  Stored in directory: /home/jas/.cache/pip/wheels/85/4c/07/72215c529bd59d67e3dac29711d7aba1b692f543c808ba9e86
  Building wheel for sly (setup.py) ... done
  Created wheel for sly: filename=sly-0.4-py3-none-any.whl size=27352 sha256=f614e413918de45c73d1e9a8dca61ca07dc760d9740553400efc234c891f7fde
  Stored in directory: /home/jas/.cache/pip/wheels/a2/23/4a/6a84282a0d2c29f003012dc565b3126e427972e8b8157ea51f
  Building wheel for tlv8 (setup.py) ... done
  Created wheel for tlv8: filename=tlv8-0.10.0-py3-none-any.whl size=11266 sha256=3ec8b3c45977a3addbc66b7b99e1d81b146607c3a269502b9b5651900a0e2d08
  Stored in directory: /home/jas/.cache/pip/wheels/e9/35/86/66a473cc2abb0c7f21ed39c30a3b2219b16bd2cdb4b33cfc2c
  Building wheel for commentjson (setup.py) ... done
  Created wheel for commentjson: filename=commentjson-0.9.0-py3-none-any.whl size=12092 sha256=28b6413132d6d7798a18cf8c76885dc69f676ea763ffcb08775a3c2c43444f4a
  Stored in directory: /home/jas/.cache/pip/wheels/7d/90/23/6358a234ca5b4ec0866d447079b97fedf9883387d1d7d074e5
  Building wheel for hexdump (setup.py) ... done
  Created wheel for hexdump: filename=hexdump-3.3-py3-none-any.whl size=8913 sha256=79dfadd42edbc9acaeac1987464f2df4053784fff18b96408c1309b74fd09f50
  Stored in directory: /home/jas/.cache/pip/wheels/26/28/f7/f47d7ecd9ae44c4457e72c8bb617ef18ab332ee2b2a1047e87
  Building wheel for pyspinel (setup.py) ... done
  Created wheel for pyspinel: filename=pyspinel-1.0.3-py3-none-any.whl size=65033 sha256=01dc27f81f28b4830a0cf2336dc737ef309a1287fcf33f57a8a4c5bed3b5f0a6
  Stored in directory: /home/jas/.cache/pip/wheels/95/ec/4b/6e3e2ee18e7292d26a65659f75d07411a6e69158bb05507590
  Building wheel for fire (setup.py) ... done
  Created wheel for fire: filename=fire-0.5.0-py2.py3-none-any.whl size=116951 sha256=3d288585478c91a6914629eb739ea789828eb2d0267febc7c5390cb24ba153e8
  Stored in directory: /home/jas/.cache/pip/wheels/90/d4/f7/9404e5db0116bd4d43e5666eaa3e70ab53723e1e3ea40c9a95
  Building wheel for intervaltree (setup.py) ... done
  Created wheel for intervaltree: filename=intervaltree-3.1.0-py2.py3-none-any.whl size=26119 sha256=5ff1def22ba883af25c90d90ef7c6518496fcd47dd2cbc53a57ec04cd60dc21d
  Stored in directory: /home/jas/.cache/pip/wheels/fa/80/8c/43488a924a046b733b64de3fac99252674c892a4c3801c0a61
  Building wheel for lark-parser (setup.py) ... done
  Created wheel for lark-parser: filename=lark_parser-0.7.8-py2.py3-none-any.whl size=62527 sha256=3d2ec1d0f926fc2688d40777f7ef93c9986f874169132b1af590b6afc038f4be
  Stored in directory: /home/jas/.cache/pip/wheels/29/30/94/33e8b58318aa05cb1842b365843036e0280af5983abb966b83
  Building wheel for naturalsort (setup.py) ... done
  Created wheel for naturalsort: filename=naturalsort-1.5.1-py3-none-any.whl size=7526 sha256=bdecac4a49f2416924548cae6c124c85d5333e9e61c563232678ed182969d453
  Stored in directory: /home/jas/.cache/pip/wheels/a6/8e/c9/98cfa614fff2979b457fa2d9ad45ec85fa417e7e3e2e43be51
  Building wheel for future (setup.py) ... done
  Created wheel for future: filename=future-0.18.3-py3-none-any.whl size=492037 sha256=57a01e68feca2b5563f5f624141267f399082d2f05f55886f71b5d6e6cf2b02c
  Stored in directory: /home/jas/.cache/pip/wheels/5e/a9/47/f118e66afd12240e4662752cc22cefae5d97275623aa8ef57d
Successfully built nrfutil crcmod sly tlv8 commentjson hexdump pyspinel fire intervaltree lark-parser naturalsort future
Installing collected packages: tlv8, sortedcontainers, sly, pyserial, pyelftools, piccata, naturalsort, libusb1, lark-parser, intelhex, hexdump, fastjsonschema, crcmod, asn1crypto, wrapt, urllib3, typing_extensions, tqdm, termcolor, ruamel.yaml.clib, python-dateutil, pyspinel, pypemicro, pycryptodome, psutil, protobuf, prettytable, oscrypto, milksnake, libusbsio, jinja2, intervaltree, humanfriendly, future, frozendict, fido2, ecdsa, deepmerge, commentjson, click-option-group, click-command-tree, capstone, astunparse, argparse-addons, ruamel.yaml, pyocd-pemicro, pylink-square, pc_ble_driver_py, fire, cmsis-pack-manager, bincopy, pyocd, nrfutil, nkdfu, spsdk, pynitrokey
  WARNING: The script nitropy is installed in '/home/jas/.local/bin' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
Successfully installed argparse-addons-0.12.0 asn1crypto-1.5.1 astunparse-1.6.3 bincopy-17.10.3 capstone-4.0.2 click-command-tree-1.1.0 click-option-group-0.5.5 cmsis-pack-manager-0.2.10 commentjson-0.9.0 crcmod-1.7 deepmerge-0.3.0 ecdsa-0.18.0 fastjsonschema-2.16.3 fido2-1.1.0 fire-0.5.0 frozendict-2.3.5 future-0.18.3 hexdump-3.3 humanfriendly-10.0 intelhex-2.3.0 intervaltree-3.1.0 jinja2-3.0.3 lark-parser-0.7.8 libusb1-1.9.3 libusbsio-2.1.11 milksnake-0.1.5 naturalsort-1.5.1 nkdfu-0.2 nrfutil-6.1.7 oscrypto-1.3.0 pc_ble_driver_py-0.17.0 piccata-2.0.3 prettytable-2.5.0 protobuf-3.20.3 psutil-5.9.4 pycryptodome-3.17 pyelftools-0.29 pylink-square-0.11.1 pynitrokey-0.4.34 pyocd-0.31.0 pyocd-pemicro-1.1.5 pypemicro-0.1.11 pyserial-3.5 pyspinel-1.0.3 python-dateutil-2.7.5 ruamel.yaml-0.17.21 ruamel.yaml.clib-0.2.7 sly-0.4 sortedcontainers-2.4.0 spsdk-1.7.1 termcolor-2.2.0 tlv8-0.10.0 tqdm-4.65.0 typing_extensions-4.3.0 urllib3-1.26.15 wrapt-1.15.0
jas@kaka:~$

Then upgrading the device worked remarkable well, although I wish that the tool would have printed URLs and checksums for the firmware files to allow easy confirmation.

jas@kaka:~$ PATH=$PATH:/home/jas/.local/bin
jas@kaka:~$ nitropy start list
Command line tool to interact with Nitrokey devices 0.4.34
:: 'Nitrokey Start' keys:
FSIJ-1.2.15-5D271572: Nitrokey Nitrokey Start (RTM.12.1-RC2-modified)
jas@kaka:~$ nitropy start update
Command line tool to interact with Nitrokey devices 0.4.34
Nitrokey Start firmware update tool
Platform: Linux-5.15.0-67-generic-x86_64-with-glibc2.35
System: Linux, is_linux: True
Python: 3.10.6
Saving run log to: /tmp/nitropy.log.gc5753a8
Admin PIN: 
Firmware data to be used:
- FirmwareType.REGNUAL: 4408, hash: ...b'72a30389' valid (from ...built/RTM.13/regnual.bin)
- FirmwareType.GNUK: 129024, hash: ...b'25a4289b' valid (from ...prebuilt/RTM.13/gnuk.bin)
Currently connected device strings:
Device: 
    Vendor: Nitrokey
   Product: Nitrokey Start
    Serial: FSIJ-1.2.15-5D271572
  Revision: RTM.12.1-RC2-modified
    Config: *:*:8e82
       Sys: 3.0
     Board: NITROKEY-START-G
initial device strings: [{'name': '', 'Vendor': 'Nitrokey', 'Product': 'Nitrokey Start', 'Serial': 'FSIJ-1.2.15-5D271572', 'Revision': 'RTM.12.1-RC2-modified', 'Config': '*:*:8e82', 'Sys': '3.0', 'Board': 'NITROKEY-START-G'}]
Please note:
- Latest firmware available is: 
  RTM.13 (published: 2022-12-08T10:59:11Z)
- provided firmware: None
- all data will be removed from the device!
- do not interrupt update process - the device may not run properly!
- the process should not take more than 1 minute
Do you want to continue? [yes/no]: yes
...
Starting bootloader upload procedure
Device: Nitrokey Start FSIJ-1.2.15-5D271572
Connected to the device
Running update!
Do NOT remove the device from the USB slot, until further notice
Downloading flash upgrade program...
Executing flash upgrade...
Waiting for device to appear:
  Wait 20 seconds.....

Downloading the program
Protecting device
Finish flashing
Resetting device
Update procedure finished. Device could be removed from USB slot.

Currently connected device strings (after upgrade):
Device: 
    Vendor: Nitrokey
   Product: Nitrokey Start
    Serial: FSIJ-1.2.19-5D271572
  Revision: RTM.13
    Config: *:*:8e82
       Sys: 3.0
     Board: NITROKEY-START-G
device can now be safely removed from the USB slot
final device strings: [{'name': '', 'Vendor': 'Nitrokey', 'Product': 'Nitrokey Start', 'Serial': 'FSIJ-1.2.19-5D271572', 'Revision': 'RTM.13', 'Config': '*:*:8e82', 'Sys': '3.0', 'Board': 'NITROKEY-START-G'}]
finishing session 2023-03-16 21:49:07.371291
Log saved to: /tmp/nitropy.log.gc5753a8
jas@kaka:~$ 

jas@kaka:~$ nitropy start list
Command line tool to interact with Nitrokey devices 0.4.34
:: 'Nitrokey Start' keys:
FSIJ-1.2.19-5D271572: Nitrokey Nitrokey Start (RTM.13)
jas@kaka:~$ 

Before importing the master key to this device, it should be configured. Note the commands in the beginning to make sure scdaemon/pcscd is not running because they may have cached state from earlier cards. Change PIN code as you like after this, my experience with Gnuk was that the Admin PIN had to be changed first, then you import the key, and then you change the PIN.

jas@kaka:~$ gpg-connect-agent "SCD KILLSCD" "SCD BYE" /bye
OK
ERR 67125247 Slut på fil <GPG Agent>
jas@kaka:~$ ps auxww|grep -e pcsc -e scd
jas        11651  0.0  0.0   3468  1672 pts/0    R+   21:54   0:00 grep --color=auto -e pcsc -e scd
jas@kaka:~$ gpg --card-edit

Reader ...........: 20A0:4211:FSIJ-1.2.19-5D271572:0
Application ID ...: D276000124010200FFFE5D2715720000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 5D271572
Name of cardholder: [not set]
Language prefs ...: [not set]
Salutation .......: 
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: off
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> admin
Admin commands are allowed

gpg/card> kdf-setup

gpg/card> passwd
gpg: OpenPGP card no. D276000124010200FFFE5D2715720000 detected

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 3
PIN changed.

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? q

gpg/card> name
Cardholder's surname: Josefsson
Cardholder's given name: Simon

gpg/card> lang
Language preferences: sv

gpg/card> sex
Salutation (M = Mr., F = Ms., or space): m

gpg/card> login
Login data (account name): jas

gpg/card> url
URL to retrieve public key: https://josefsson.org/key-20190320.txt

gpg/card> forcesig

gpg/card> key-attr
Changing card key attribute for: Signature key
Please select what kind of key you want:
   (1) RSA
   (2) ECC
Your selection? 2
Please select which elliptic curve you want:
   (1) Curve 25519
   (4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519
Note: There is no guarantee that the card supports the requested size.
      If the key generation does not succeed, please check the
      documentation of your card to see what sizes are allowed.
Changing card key attribute for: Encryption key
Please select what kind of key you want:
   (1) RSA
   (2) ECC
Your selection? 2
Please select which elliptic curve you want:
   (1) Curve 25519
   (4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: cv25519
Changing card key attribute for: Authentication key
Please select what kind of key you want:
   (1) RSA
   (2) ECC
Your selection? 2
Please select which elliptic curve you want:
   (1) Curve 25519
   (4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519

gpg/card> 
jas@kaka:~$ gpg --card-edit

Reader ...........: 20A0:4211:FSIJ-1.2.19-5D271572:0
Application ID ...: D276000124010200FFFE5D2715720000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 5D271572
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: on
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

jas@kaka:~$ 

Once setup, bring out your offline machine and boot it and mount your USB stick with the offline key. The paths below will be different, and this is using a somewhat unorthodox approach of working with fresh GnuPG configuration paths that I chose for the USB stick.

jas@kaka:/media/jas/2c699cbd-b77e-4434-a0d6-0c4965864296$ cp -a gnupghome-backup-masterkey gnupghome-import-nitrokey-5D271572
jas@kaka:/media/jas/2c699cbd-b77e-4434-a0d6-0c4965864296$ gpg --homedir $PWD/gnupghome-import-nitrokey-5D271572 --edit-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Secret key is available.

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> keytocard
Really move the primary key? (y/N) y
Please select where to store the key:
   (1) Signature key
   (3) Authentication key
Your selection? 1

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> 
Save changes? (y/N) y
jas@kaka:/media/jas/2c699cbd-b77e-4434-a0d6-0c4965864296$ 

Don’t forget to change the PIN at this point. At this point it is useful to confirm that the Nitrokey has the master key available and that is possible to sign statements with it, back on your regular machine:

jas@kaka:~$ gpg --card-status
Reader ...........: 20A0:4211:FSIJ-1.2.19-5D271572:0
Application ID ...: D276000124010200FFFE5D2715720000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 5D271572
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 1
KDF setting ......: on
Signature key ....: B1D2 BD13 75BE CB78 4CF4  F8C4 D73C F638 C53C 06BE
      created ....: 2019-03-20 23:37:24
Encryption key....: [none]
Authentication key: [none]
General key info..: pub  ed25519/D73CF638C53C06BE 2019-03-20 Simon Josefsson <simon@josefsson.org>
sec>  ed25519/D73CF638C53C06BE  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 5D271572
ssb>  ed25519/80260EE8A9B92B2B  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 42315277
ssb>  ed25519/51722B08FE4745A2  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 42315277
ssb>  cv25519/02923D7EE76EBD60  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 42315277
jas@kaka:~$ echo foo|gpg -a --sign|gpg --verify
gpg: Signature made Thu Mar 16 22:11:02 2023 CET
gpg:                using EDDSA key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
gpg: Good signature from "Simon Josefsson <simon@josefsson.org>" [ultimate]
jas@kaka:~$ 

Finally to retrieve and sign a key, for example Andre Heinecke’s that I could confirm the OpenPGP key identifier from his business card.

jas@kaka:~$ gpg --locate-external-keys aheinecke@gnupg.com
gpg: key 1FDF723CF462B6B1: public key "Andre Heinecke <aheinecke@gnupg.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   2  signed:   7  trust: 0-, 0q, 0n, 0m, 0f, 2u
gpg: depth: 1  valid:   7  signed:  64  trust: 7-, 0q, 0n, 0m, 0f, 0u
gpg: next trustdb check due at 2023-05-26
pub   rsa3072 2015-12-08 [SC] [expires: 2025-12-05]
      94A5C9A03C2FE5CA3B095D8E1FDF723CF462B6B1
uid           [ unknown] Andre Heinecke <aheinecke@gnupg.com>
sub   ed25519 2017-02-13 [S]
sub   ed25519 2017-02-13 [A]
sub   rsa3072 2015-12-08 [E] [expires: 2025-12-05]
sub   rsa3072 2015-12-08 [A] [expires: 2025-12-05]

jas@kaka:~$ gpg --edit-key "94A5C9A03C2FE5CA3B095D8E1FDF723CF462B6B1"
gpg (GnuPG) 2.2.27; Copyright (C) 2021 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.


pub  rsa3072/1FDF723CF462B6B1
     created: 2015-12-08  expires: 2025-12-05  usage: SC  
     trust: unknown       validity: unknown
sub  ed25519/2978E9D40CBABA5C
     created: 2017-02-13  expires: never       usage: S   
sub  ed25519/DC74D901C8E2DD47
     created: 2017-02-13  expires: never       usage: A   
The following key was revoked on 2017-02-23 by RSA key 1FDF723CF462B6B1 Andre Heinecke <aheinecke@gnupg.com>
sub  cv25519/1FFE3151683260AB
     created: 2017-02-13  revoked: 2017-02-23  usage: E   
sub  rsa3072/8CC999BDAA45C71F
     created: 2015-12-08  expires: 2025-12-05  usage: E   
sub  rsa3072/6304A4B539CE444A
     created: 2015-12-08  expires: 2025-12-05  usage: A   
[ unknown] (1). Andre Heinecke <aheinecke@gnupg.com>

gpg> sign

pub  rsa3072/1FDF723CF462B6B1
     created: 2015-12-08  expires: 2025-12-05  usage: SC  
     trust: unknown       validity: unknown
 Primary key fingerprint: 94A5 C9A0 3C2F E5CA 3B09  5D8E 1FDF 723C F462 B6B1

     Andre Heinecke <aheinecke@gnupg.com>

This key is due to expire on 2025-12-05.
Are you sure that you want to sign this key with your
key "Simon Josefsson <simon@josefsson.org>" (D73CF638C53C06BE)

Really sign? (y/N) y

gpg> quit
Save changes? (y/N) y
jas@kaka:~$ 

This is on my day-to-day machine, using the NitroKey Start with the offline key. No need to boot the old offline machine just to sign keys or extend expiry anymore! At FOSDEM’23 I managed to get at least one DD signature on my new key, and the Debian keyring maintainers accepted my Ed25519 key. Hopefully I can now finally let my 2014-era RSA3744 key expire in 2023-09-19 and not extend it any further. This should finish my transition to a simpler OpenPGP key setup, yay!

OpenPGP key on FST-01SZ

I use GnuPG to compute cryptographic signatures for my emails, git commits/tags, and software release artifacts (tarballs). Part of GnuPG is gpg-agent which talks to OpenSSH, which I login to remote servers and to clone git repositories. I dislike storing cryptographic keys on general-purpose machines, and have used hardware-backed OpenPGP keys since around 2006 when I got a FSFE Fellowship Card. GnuPG via gpg-agent handles this well, and the private key never leaves the hardware. The ZeitControl cards were (to my knowledge) proprietary hardware running some non-free operating system and OpenPGP implementation. By late 2012 the YubiKey NEO supported OpenPGP, and while the hardware and operating system on it was not free, at least it ran a free software OpenPGP implementation and eventually I setup my primary RSA key on it. This worked well for a couple of years, and when I in 2019 wished to migrate to a new key, the FST-01G device with open hardware running free software that supported Ed25519 had become available. I created a key and have been using the FST-01G on my main laptop since then. This little device has been working, the signature counter on it is around 14501 which means around 10 signatures/day since then!

Currently I am in the process of migrating towards a new laptop, and moving the FST-01G device between them is cumbersome, especially if I want to use both laptops in parallel. That’s why I need to setup a new hardware device to hold my OpenPGP key, which can go with my new laptop. This is a good time to re-visit alternatives. I quickly decided that I did not want to create a new key, only to import my current one to keep everything working. My requirements on the device to chose hasn’t changed since 2019, see my summary at the end of the earlier blog post. Unfortunately the FST-01G is out of stock and the newer FST-01SZ has also out of stock. While Tillitis looks promising (and I have one to play with), it does not support OpenPGP (yet). What to do? Fortunately, I found some FST-01SZ device in my drawer, and decided to use it pending a more satisfactory answer. Hopefully once I get around to generate a new OpenPGP key in a year or so, I will do a better survey of options that are available on the market then. What are your (freedom-respecting) OpenPGP hardware recommendations?

FST-01SZ circuit board

Similar to setting up the FST-01G, the FST-01SZ needs to be setup before use. I’m doing the following from Trisquel 11 but any GNU/Linux system would work. When the device is inserted at first time, some kernel messages are shown (see /var/log/syslog or use the dmesg command):


usb 3-3: new full-speed USB device number 39 using xhci_hcd
usb 3-3: New USB device found, idVendor=234b, idProduct=0004, bcdDevice= 2.00
usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-3: Product: Fraucheky
usb 3-3: Manufacturer: Free Software Initiative of Japan
usb 3-3: SerialNumber: FSIJ-0.0
usb-storage 3-3:1.0: USB Mass Storage device detected
scsi host1: usb-storage 3-3:1.0
scsi 1:0:0:0: Direct-Access     FSIJ     Fraucheky        1.0  PQ: 0 ANSI: 0
sd 1:0:0:0: Attached scsi generic sg2 type 0
sd 1:0:0:0: [sdc] 128 512-byte logical blocks: (65.5 kB/64.0 KiB)
sd 1:0:0:0: [sdc] Write Protect is off
sd 1:0:0:0: [sdc] Mode Sense: 03 00 00 00
sd 1:0:0:0: [sdc] No Caching mode page found
sd 1:0:0:0: [sdc] Assuming drive cache: write through
 sdc:
sd 1:0:0:0: [sdc] Attached SCSI removable disk

Interestingly, the NeuG software installed on the device I got appears to be version 1.0.9:


jas@kaka:~$ head /media/jas/Fraucheky/README
NeuG - a true random number generator implementation
						  Version 1.0.9
						     2018-11-20
					           Niibe Yutaka
			      Free Software Initiative of Japan
What's NeuG?
============
jas@kaka:~$ 

I could not find version 1.0.9 published anywhere, but the device came with a SD-card that contain a copy of the source, so I uploaded it until a more canonical place is located. Putting the device in the serial mode can be done using a sudo eject /dev/sdc command which results in the following syslog output.


usb 3-3: reset full-speed USB device number 39 using xhci_hcd
usb 3-3: device firmware changed
usb 3-3: USB disconnect, device number 39
sdc: detected capacity change from 128 to 0
usb 3-3: new full-speed USB device number 40 using xhci_hcd
usb 3-3: New USB device found, idVendor=234b, idProduct=0001, bcdDevice= 2.00
usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-3: Product: NeuG True RNG
usb 3-3: Manufacturer: Free Software Initiative of Japan
usb 3-3: SerialNumber: FSIJ-1.0.9-42315277
cdc_acm 3-3:1.0: ttyACM0: USB ACM device

Now download Gnuk, verify its integrity and build it. You may need some additional packages installed, try apt-get install gcc-arm-none-eabi openocd python3-usb. As you can see, I’m using the stable 1.2 branch of Gnuk, currently on version 1.2.20. The ./configure parameters deserve some explanation. The kdf_do=required sets up the device to require KDF usage. The --enable-factory-reset allows me to use the command factory-reset (with admin PIN) inside gpg --card-edit to completely wipe the card. Some may consider that too dangerous, but my view is that if someone has your admin PIN it is game over anyway. The --vidpid=234b:0000 is specifies the USB VID/PID to use, and --target=FST_01SZ is critical to set the platform (you’ll may brick the device if you pick the wrong --target setting).


jas@kaka:~/src$ rm -rf gnuk neug
jas@kaka:~/src$ git clone https://gitlab.com/jas/neug.git
Cloning into 'neug'...
remote: Enumerating objects: 2034, done.
remote: Counting objects: 100% (2034/2034), done.
remote: Compressing objects: 100% (603/603), done.
remote: Total 2034 (delta 1405), reused 2013 (delta 1405), pack-reused 0
Receiving objects: 100% (2034/2034), 910.34 KiB | 3.50 MiB/s, done.
Resolving deltas: 100% (1405/1405), done.
jas@kaka:~/src$ git clone https://salsa.debian.org/gnuk-team/gnuk/gnuk.git
Cloning into 'gnuk'...
remote: Enumerating objects: 13765, done.
remote: Counting objects: 100% (959/959), done.
remote: Compressing objects: 100% (337/337), done.
remote: Total 13765 (delta 629), reused 907 (delta 599), pack-reused 12806
Receiving objects: 100% (13765/13765), 12.59 MiB | 3.05 MiB/s, done.
Resolving deltas: 100% (10077/10077), done.
jas@kaka:~/src$ cd neug
jas@kaka:~/src/neug$ git describe 
release/1.0.9
jas@kaka:~/src/neug$ git tag -v `git describe`
object 5d51022a97a5b7358d0ea62bbbc00628c6cec06a
type commit
tag release/1.0.9
tagger NIIBE Yutaka <gniibe@fsij.org> 1542701768 +0900

Version 1.0.9.
gpg: Signature made Tue Nov 20 09:16:08 2018 CET
gpg:                using EDDSA key 249CB3771750745D5CDD323CE267B052364F028D
gpg:                issuer "gniibe@fsij.org"
gpg: Good signature from "NIIBE Yutaka <gniibe@fsij.org>" [unknown]
gpg:                 aka "NIIBE Yutaka <gniibe@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 249C B377 1750 745D 5CDD  323C E267 B052 364F 028D
jas@kaka:~/src/neug$ cd ../gnuk/
jas@kaka:~/src/gnuk$ git checkout STABLE-BRANCH-1-2 
Branch 'STABLE-BRANCH-1-2' set up to track remote branch 'STABLE-BRANCH-1-2' from 'origin'.
Switched to a new branch 'STABLE-BRANCH-1-2'
jas@kaka:~/src/gnuk$ git describe
release/1.2.20
jas@kaka:~/src/gnuk$ git tag -v `git describe`
object 9d3c08bd2beb73ce942b016d4328f0a596096c02
type commit
tag release/1.2.20
tagger NIIBE Yutaka <gniibe@fsij.org> 1650594032 +0900

Gnuk: Version 1.2.20
gpg: Signature made Fri Apr 22 04:20:32 2022 CEST
gpg:                using EDDSA key 249CB3771750745D5CDD323CE267B052364F028D
gpg: Good signature from "NIIBE Yutaka <gniibe@fsij.org>" [unknown]
gpg:                 aka "NIIBE Yutaka <gniibe@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 249C B377 1750 745D 5CDD  323C E267 B052 364F 028D
jas@kaka:~/src/gnuk/src$ git submodule update --init
Submodule 'chopstx' (https://salsa.debian.org/gnuk-team/chopstx/chopstx.git) registered for path '../chopstx'
Cloning into '/home/jas/src/gnuk/chopstx'...
Submodule path '../chopstx': checked out 'e12a7e0bb3f004c7bca41cfdb24c8b66daf3db89'
jas@kaka:~/src/gnuk$ cd chopstx
jas@kaka:~/src/gnuk/chopstx$ git describe
release/1.21
jas@kaka:~/src/gnuk/chopstx$ git tag -v `git describe`
object e12a7e0bb3f004c7bca41cfdb24c8b66daf3db89
type commit
tag release/1.21
tagger NIIBE Yutaka <gniibe@fsij.org> 1650593697 +0900

Chopstx: Version 1.21
gpg: Signature made Fri Apr 22 04:14:57 2022 CEST
gpg:                using EDDSA key 249CB3771750745D5CDD323CE267B052364F028D
gpg: Good signature from "NIIBE Yutaka <gniibe@fsij.org>" [unknown]
gpg:                 aka "NIIBE Yutaka <gniibe@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 249C B377 1750 745D 5CDD  323C E267 B052 364F 028D
jas@kaka:~/src/gnuk/chopstx$ cd ../src
jas@kaka:~/src/gnuk/src$ kdf_do=required ./configure --enable-factory-reset --vidpid=234b:0000 --target=FST_01SZ
Header file is: board-fst-01sz.h
Debug option disabled
Configured for bare system (no-DFU)
PIN pad option disabled
CERT.3 Data Object is NOT supported
Card insert/removal by HID device is NOT supported
Life cycle management is supported
Acknowledge button is supported
KDF DO is required before key import/generation
jas@kaka:~/src/gnuk/src$ make | less
jas@kaka:~/src/gnuk/src$ cd ../regnual/
jas@kaka:~/src/gnuk/regnual$ make | less
jas@kaka:~/src/gnuk/regnual$ cd ../../
jas@kaka:~/src$ sudo python3 neug/tool/neug_upgrade.py -f gnuk/regnual/regnual.bin gnuk/src/build/gnuk.bin
gnuk/regnual/regnual.bin: 4608
gnuk/src/build/gnuk.bin: 109568
CRC32: b93ca829

Device: 
Configuration: 1
Interface: 1
20000e00:20005000
Downloading flash upgrade program...
start 20000e00
end   20002000
# 20002000: 32 : 4
Run flash upgrade program...
Wait 1 second...
Wait 1 second...
Device: 
08001000:08020000
Downloading the program
start 08001000
end   0801ac00
jas@kaka:~/src$ 

The kernel log will contain the following, and the card is ready to use as an OpenPGP card. You may unplug it and re-insert it as you wish.


usb 3-3: reset full-speed USB device number 41 using xhci_hcd
usb 3-3: device firmware changed
usb 3-3: USB disconnect, device number 41
usb 3-3: new full-speed USB device number 42 using xhci_hcd
usb 3-3: New USB device found, idVendor=234b, idProduct=0000, bcdDevice= 2.00
usb 3-3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 3-3: Product: Gnuk Token
usb 3-3: Manufacturer: Free Software Initiative of Japan
usb 3-3: SerialNumber: FSIJ-1.2.20-42315277

Setting up the card is the next step, and there are many tutorials around for this, eventually I settled with the following sequence. Let’s start with setting the admin PIN. First make sure that pcscd nor scdaemon is running, which is good hygien since those processes cache some information and with a stale connection this easily leads to confusion. Cache invalidation… sigh.


jas@kaka:~$ gpg-connect-agent "SCD KILLSCD" "SCD BYE" /bye
jas@kaka:~$ ps auxww|grep -e pcsc -e scd
jas        30221  0.0  0.0   3468  1692 pts/3    R+   11:49   0:00 grep --color=auto -e pcsc -e scd
jas@kaka:~$ gpg --card-edit

Reader ...........: 234B:0000:FSIJ-1.2.20-42315277:0
Application ID ...: D276000124010200FFFE423152770000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 42315277
Name of cardholder: [not set]
Language prefs ...: [not set]
Salutation .......: 
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: off
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> admin
Admin commands are allowed

gpg/card> kdf-setup

gpg/card> passwd
gpg: OpenPGP card no. D276000124010200FFFE423152770000 detected

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 3
PIN changed.

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 

Now it would be natural to setup the PIN and reset code. However the Gnuk software is configured to not allow this until the keys are imported. You would get the following somewhat cryptical error messages if you try. This took me a while to understand, since this is device-specific, and some other OpenPGP implementations allows you to configure a PIN and reset code before key import.


Your selection? 4
Error setting the Reset Code: Card error

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? 1
Error changing the PIN: Conditions of use not satisfied

1 - change PIN
2 - unblock PIN
3 - change Admin PIN
4 - set the Reset Code
Q - quit

Your selection? q

Continue to configure the card and make it ready for key import. Some settings deserve comments. The lang field may be used to setup the language, but I have rarely seen it use, and I set it to ‘sv‘ (Swedish) mostly to be able to experiment if any software adhears to it. The URL is important to point to somewhere where your public key is stored, the fetch command of gpg --card-edit downloads it and sets up GnuPG with it when you are on a clean new laptop. The forcesig command changes the default so that a PIN code is not required for every digital signature operation, remember that I averaged 10 signatures per day for the past 2-3 years? Think of the wasted energy typing those PIN codes every time! Changing the cryptographic key type is required when I import 25519-based keys.


gpg/card> name
Cardholder's surname: Josefsson
Cardholder's given name: Simon

gpg/card> lang
Language preferences: sv

gpg/card> sex
Salutation (M = Mr., F = Ms., or space): m

gpg/card> login
Login data (account name): jas

gpg/card> url
URL to retrieve public key: https://josefsson.org/key-20190320.txt

gpg/card> forcesig

gpg/card> key-attr
Changing card key attribute for: Signature key
Please select what kind of key you want:
   (1) RSA
   (2) ECC
Your selection? 2
Please select which elliptic curve you want:
   (1) Curve 25519
   (4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519
Note: There is no guarantee that the card supports the requested size.
      If the key generation does not succeed, please check the
      documentation of your card to see what sizes are allowed.
Changing card key attribute for: Encryption key
Please select what kind of key you want:
   (1) RSA
   (2) ECC
Your selection? 2
Please select which elliptic curve you want:
   (1) Curve 25519
   (4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: cv25519
Changing card key attribute for: Authentication key
Please select what kind of key you want:
   (1) RSA
   (2) ECC
Your selection? 2
Please select which elliptic curve you want:
   (1) Curve 25519
   (4) NIST P-384
Your selection? 1
The card will now be re-configured to generate a key of type: ed25519

gpg/card> 

Reader ...........: 234B:0000:FSIJ-1.2.20-42315277:0
Application ID ...: D276000124010200FFFE423152770000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 42315277
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
KDF setting ......: on
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> 

The device is now ready for key import! Bring out your offline laptop and boot it and use the keytocard command on the subkeys to import them. This assumes you saved a copy of the GnuPG home directory after generating the master and subkeys before, which I did in my own previous tutorial when I generated the keys. This may be a bit unusual, and there are simpler ways to do this (e.g., import a copy of the secret keys into a fresh GnuPG home directory).


$ cp -a gnupghome-backup-mastersubkeys gnupghome-import-fst01sz-42315277-2022-12-24
$ ps auxww|grep -e pcsc -e scd
$ gpg --homedir $PWD/gnupghome-import-fst01sz-42315277-2022-12-24 --edit-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
...
Secret key is available.

gpg: checking the trustdb
gpg: marginals needed: 3  completes needed: 1  trust model: pgp
gpg: depth: 0  valid:   1  signed:   0  trust: 0-, 0q, 0n, 0m, 0f, 1u
sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> key 1

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb* cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> keytocard
Please select where to store the key:
   (2) Encryption key
Your selection? 2

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb* cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> key 1

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> key 2

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb* ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> keytocard
Please select where to store the key:
   (3) Authentication key
Your selection? 3

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb* ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> key 2

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb  ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> key 3

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb* ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> keytocard
Please select where to store the key:
   (1) Signature key
   (3) Authentication key
Your selection? 1

sec  ed25519/D73CF638C53C06BE
     created: 2019-03-20  expired: 2019-10-22  usage: SC  
     trust: ultimate      validity: expired
ssb  cv25519/02923D7EE76EBD60
     created: 2019-03-20  expired: 2019-10-22  usage: E   
ssb  ed25519/80260EE8A9B92B2B
     created: 2019-03-20  expired: 2019-10-22  usage: A   
ssb* ed25519/51722B08FE4745A2
     created: 2019-03-20  expired: 2019-10-22  usage: S   
[ expired] (1). Simon Josefsson <simon@josefsson.org>

gpg> quit
Save changes? (y/N) y
$ 

Now insert it into your daily laptop and have GnuPG and learn about the new private keys and forget about any earlier locally available card bindings — this usually manifests itself by GnuPG asking you to insert a OpenPGP card with another serial number. Earlier I did rm -rf ~/.gnupg/private-keys-v1.d/ but the scd serialno followed by learn --force is nicer. I also sets up trust setting for my own key.


jas@kaka:~$ gpg-connect-agent "scd serialno" "learn --force" /bye
...
jas@kaka:~$ echo "B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE:6:" | gpg --import-ownertrust
jas@kaka:~$ gpg --card-status
Reader ...........: 234B:0000:FSIJ-1.2.20-42315277:0
Application ID ...: D276000124010200FFFE423152770000
Application type .: OpenPGP
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 42315277
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Salutation .......: Mr.
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 5 5 5
Signature counter : 3
KDF setting ......: on
Signature key ....: A3CC 9C87 0B9D 310A BAD4  CF2F 5172 2B08 FE47 45A2
      created ....: 2019-03-20 23:40:49
Encryption key....: A9EC 8F4D 7F1E 50ED 3DEF  49A9 0292 3D7E E76E BD60
      created ....: 2019-03-20 23:40:26
Authentication key: CA7E 3716 4342 DF31 33DF  3497 8026 0EE8 A9B9 2B2B
      created ....: 2019-03-20 23:40:37
General key info..: sub  ed25519/51722B08FE4745A2 2019-03-20 Simon Josefsson <simon@josefsson.org>
sec#  ed25519/D73CF638C53C06BE  created: 2019-03-20  expires: 2023-09-19
ssb>  ed25519/80260EE8A9B92B2B  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 42315277
ssb>  ed25519/51722B08FE4745A2  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 42315277
ssb>  cv25519/02923D7EE76EBD60  created: 2019-03-20  expires: 2023-09-19
                                card-no: FFFE 42315277
jas@kaka:~$ 

Verify that you can digitally sign and authenticate using the key and you are done!


jas@kaka:~$ echo foo|gpg -a --sign|gpg --verify
gpg: Signature made Sat Dec 24 13:49:59 2022 CET
gpg:                using EDDSA key A3CC9C870B9D310ABAD4CF2F51722B08FE4745A2
gpg: Good signature from "Simon Josefsson <simon@josefsson.org>" [ultimate]
jas@kaka:~$ ssh-add -L
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILzCFcHHrKzVSPDDarZPYqn89H5TPaxwcORgRg+4DagE cardno:FFFE42315277
jas@kaka:~$ 

So time to relax and celebrate christmas? Hold on… not so fast! Astute readers will have noticed that the output said ‘PIN retry counter: 5 5 5‘. That’s not the default PIN retry counter for Gnuk! How did that happen? Indeed, good catch and great question, my dear reader. I wanted to include how you can modify the Gnuk source code, re-build it and re-flash the Gnuk as well. This method is different than flashing Gnuk onto a device that is running NeuG so the commands I used to flash the firmware in the start of this blog post no longer works in a device running Gnuk. Fortunately modern Gnuk supports updating firmware by specifying the Admin PIN code only, and provides a simple script to achieve this as well. The PIN retry counter setting is hard coded in the openpgp-do.c file, and we run a a perl command to modify the file, rebuild Gnuk and upgrade the FST-01SZ. This of course wipes all your settings, so you will have the opportunity to practice all the commands earlier in this post once again!


jas@kaka:~/src/gnuk/src$ perl -pi -e 's/PASSWORD_ERRORS_MAX 3/PASSWORD_ERRORS_MAX 5/' openpgp-do.c
jas@kaka:~/src/gnuk/src$ make | less
jas@kaka:~/src/gnuk/src$ cd ../tool/
jas@kaka:~/src/gnuk/tool$ ./upgrade_by_passwd.py 
Admin password: 
Device: 
Configuration: 1
Interface: 0
../regnual/regnual.bin: 4608
../src/build/gnuk.bin: 110592
CRC32: b93ca829

Device: 
Configuration: 1
Interface: 0
20002a00:20005000
Downloading flash upgrade program...
start 20002a00
end   20003c00
Run flash upgrade program...
Waiting for device to appear:
  Wait 1 second...
  Wait 1 second...
Device: 
08001000:08020000
Downloading the program
start 08001000
end   0801b000
Protecting device
Finish flashing
Resetting device
Update procedure finished
jas@kaka:~/src/gnuk/tool$

Now finally, I wish you all a Merry Christmas and Happy Hacking!

Offline Ed25519 OpenPGP key with subkeys on FST-01G running Gnuk

Below I describe how to generate an OpenPGP key and import its subkeys to a FST-01G device running Gnuk. See my earlier post on planning for my new OpenPGP key and the post on preparing the FST-01G to run Gnuk. For comparison with a RSA/YubiKey based approach, you can read about my setup from 2014.

Most of the steps below are covered by the Gnuk manual. The primary complication for me is the use of a offline machine and storing GnuPG directory stored on a USB memory device.

Offline machine

I use a laptop that is not connected to the Internet and boot it from a read-only USB memory stick. Finding a live CD that contains the necessary tools for using GnuPG with smartcards (gpg-agent, scdaemon, pcscd) is significantly harder than it should be. Using a rarely audited image begs the question of whether you can trust it. A patched kernel/gpg to generate poor randomness would be an easy and hard to notice hack. I’m using the PGP/PKI Clean Room Live CD. Recommendations on more widely used and audited alternatives would be appreciated. Select “Advanced Options” and “Run Shell” to escape the menus. Insert a new USB memory device, and prepare it as follows:

pgp@pgplive:/home/pgp$ sudo wipefs -a /dev/sdX
pgp@pgplive:/home/pgp$ sudo fdisk /dev/sdX
# create a primary partition of Linux type
pgp@pgplive:/home/pgp$ sudo mkfs.ext4 /dev/sdX1
pgp@pgplive:/home/pgp$ sudo mount /dev/sdX1 /mnt
pgp@pgplive:/home/pgp$ sudo mkdir /mnt/gnupghome
pgp@pgplive:/home/pgp$ sudo chown pgp.pgp /mnt/gnupghome
pgp@pgplive:/home/pgp$ sudo chmod go-rwx /mnt/gnupghome

GnuPG configuration

Set your GnuPG home directory to point to the gnupghome directory on the USB memory device. You will need to do this in every terminal windows you open that you want to use GnuPG in.

pgp@pgplive:/home/pgp$ export GNUPGHOME=/mnt/gnupghome
pgp@pgplive:/home/pgp$

At this point, you should be able to run gpg --card-status and get output from the smartcard.

Create master key

Create a master key and make a backup copy of the GnuPG home directory with it, together with an export ASCII version.

pgp@pgplive:/home/pgp$ gpg --quick-gen-key "Simon Josefsson <simon@josefsson.org>" ed25519 sign 216d
gpg: keybox '/mnt/gnupghome/pubring.kbx' created
gpg: /mnt/gnupghome/trustdb.gpg: trustdb created
gpg: key D73CF638C53C06BE marked as ultimately trusted
gpg: directory '/mnt/gnupghome/openpgp-revocs.d' created
gpg: revocation certificate stored as '/mnt/gnupghome/openpgp-revocs.d/B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE.rev'
pub   ed25519 2019-03-20 [SC] [expires: 2019-10-22]
      B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
      B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
uid                      Simon Josefsson <simon@josefsson.org>

pgp@pgplive:/home/pgp$ gpg -a --export-secret-keys B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE > $GNUPGHOME/masterkey.txt
pgp@pgplive:/home/pgp$ sudo cp -a $GNUPGHOME $GNUPGHOME-backup-masterkey
pgp@pgplive:/home/pgp$ 

Create subkeys

Create subkeys and make a backup of them too, as follows.

pgp@pgplive:/home/pgp$ gpg --quick-add-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE cv25519 encr 216d
pgp@pgplive:/home/pgp$ gpg --quick-add-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE ed25519 auth 216d
pgp@pgplive:/home/pgp$ gpg --quick-add-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE ed25519 sign 216d
pgp@pgplive:/home/pgp$ gpg -a --export-secret-keys B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE > $GNUPGHOME/mastersubkeys.txt
pgp@pgplive:/home/pgp$ gpg -a --export-secret-subkeys B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE > $GNUPGHOME/subkeys.txt
pgp@pgplive:/home/pgp$ sudo cp -a $GNUPGHOME $GNUPGHOME-backup-mastersubkeys
pgp@pgplive:/home/pgp$ 

Move keys to card

Prepare the card by setting Admin PIN, PIN, your full name, sex, login account, and key URL as you prefer, following the Gnuk manual on card personalization.

Move the subkeys from your GnuPG keyring to the FST01G using the keytocard command.

Take a final backup — because moving the subkeys to the card modifes the local GnuPG keyring — and create a ASCII armored version of the public key, to be transferred to your daily machine.

pgp@pgplive:/home/pgp$ gpg --list-secret-keys
/mnt/gnupghome/pubring.kbx
--------------------------
sec   ed25519 2019-03-20 [SC] [expires: 2019-10-22]
      B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
uid           [ultimate] Simon Josefsson <simon@josefsson.org>
ssb>  cv25519 2019-03-20 [E] [expires: 2019-10-22]
ssb>  ed25519 2019-03-20 [A] [expires: 2019-10-22]
ssb>  ed25519 2019-03-20 [S] [expires: 2019-10-22]

pgp@pgplive:/home/pgp$ gpg -a --export-secret-keys B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE > $GNUPGHOME/masterstubs.txt
pgp@pgplive:/home/pgp$ gpg -a --export-secret-subkeys B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE > $GNUPGHOME/subkeysstubs.txt
pgp@pgplive:/home/pgp$ gpg -a --export B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE > $GNUPGHOME/publickey.txt
pgp@pgplive:/home/pgp$ cp -a $GNUPGHOME $GNUPGHOME-backup-masterstubs
pgp@pgplive:/home/pgp$ 

Transfer to daily machine

Copy publickey.txt to your day-to-day laptop and import it and create stubs using --card-status.

jas@latte:~$ gpg --import < publickey.txt 
gpg: key D73CF638C53C06BE: public key "Simon Josefsson <simon@josefsson.org>" imported
gpg: Total number processed: 1
gpg:               imported: 1
jas@latte:~$ gpg --card-status

Reader ...........: Free Software Initiative of Japan Gnuk (FSIJ-1.2.14-67252015) 00 00
Application ID ...: D276000124010200FFFE672520150000
Version ..........: 2.0
Manufacturer .....: unmanaged S/N range
Serial number ....: 67252015
Name of cardholder: Simon Josefsson
Language prefs ...: sv
Sex ..............: male
URL of public key : https://josefsson.org/key-20190320.txt
Login data .......: jas
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 3 3
Signature counter : 0
Signature key ....: A3CC 9C87 0B9D 310A BAD4  CF2F 5172 2B08 FE47 45A2
      created ....: 2019-03-20 23:40:49
Encryption key....: A9EC 8F4D 7F1E 50ED 3DEF  49A9 0292 3D7E E76E BD60
      created ....: 2019-03-20 23:40:26
Authentication key: CA7E 3716 4342 DF31 33DF  3497 8026 0EE8 A9B9 2B2B
      created ....: 2019-03-20 23:40:37
General key info..: sub  ed25519/51722B08FE4745A2 2019-03-20 Simon Josefsson <simon@josefsson.org>
sec   ed25519/D73CF638C53C06BE  created: 2019-03-20  expires: 2019-10-22
ssb>  cv25519/02923D7EE76EBD60  created: 2019-03-20  expires: 2019-10-22
                                card-no: FFFE 67252015
ssb>  ed25519/80260EE8A9B92B2B  created: 2019-03-20  expires: 2019-10-22
                                card-no: FFFE 67252015
ssb>  ed25519/51722B08FE4745A2  created: 2019-03-20  expires: 2019-10-22
                                card-no: FFFE 67252015
jas@latte:~$ 

Before the key can be used after the import, you must update the trust database for the secret key.

Now you should have a offline master key with subkey stubs. Note in the output below that the master key is not available (sec#) and the subkeys are stubs for smartcard keys (ssb>).

jas@latte:~$ gpg --list-secret-keys
sec#  ed25519 2019-03-20 [SC] [expires: 2019-10-22]
      B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE
uid           [ultimate] Simon Josefsson <simon@josefsson.org>
ssb>  cv25519 2019-03-20 [E] [expires: 2019-10-22]
ssb>  ed25519 2019-03-20 [A] [expires: 2019-10-22]
ssb>  ed25519 2019-03-20 [S] [expires: 2019-10-22]

jas@latte:~$

If your environment variables are setup correctly, SSH should find the authentication key automatically.

jas@latte:~$ ssh-add -L
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILzCFcHHrKzVSPDDarZPYqn89H5TPaxwcORgRg+4DagE cardno:FFFE67252015
jas@latte:~$ 

GnuPG and SSH are now ready to be used with the new key. Thanks for reading!

OpenPGP 2019 Key Transition Statement

I have created a new OpenPGP key and will be transitioning away from my old key. If you have signed my old key, I would appreciate signatures on my new key as well. I have created a transition statement that can be downloaded from https://josefsson.org/key-transition-2019-03-20.txt.

Below is the signed statement.

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

OpenPGP Key Transition Statement for Simon Josefsson <simon@josefsson.org>

I have created a new OpenPGP key and will be transitioning away from
my old key.  The old key has not been compromised and will continue to
be valid for some time, but I prefer all future correspondence to be
encrypted to the new key, and will be making signatures with the new
key going forward.

I would like this new key to be re-integrated into the web of trust.
This message is signed by both keys to certify the transition.  My new
and old keys are signed by each other.  If you have signed my old key,
I would appreciate signatures on my new key as well, provided that
your signing policy permits that without re-authenticating me.

The old key, which I am transitioning away from, is:

pub   rsa3744 2014-06-22 [SC]
      9AA9 BDB1 1BB1 B99A 2128  5A33 0664 A769 5426 5E8C

The new key, to which I am transitioning, is:

pub   ed25519 2019-03-20 [SC]
      B1D2 BD13 75BE CB78 4CF4  F8C4 D73C F638 C53C 06BE

The key may be downloaded from: https://josefsson.org/key-20190320.txt

To fetch the full new key from a public key server using GnuPG, run:

  gpg --keyserver keys.gnupg.net \
      --recv-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE

If you already know my old key, you can now verify that the new key is
signed by the old one:

  gpg --check-sigs B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE

If you are satisfied that you've got the right key, and the User IDs
match what you expect, I would appreciate it if you would sign my key:

  gpg --sign-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE

You can upload your signatures to a public keyserver directly:

  gpg --keyserver keys.gnupg.net \
      --send-key B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE

Or email simon@josefsson.org (possibly encrypted) the output from:

  gpg --armor --export B1D2BD1375BECB784CF4F8C4D73CF638C53C06BE

If you'd like any further verification or have any questions about the
transition please contact me directly.

To verify the integrity of this statement:

  wget -q -O- https://josefsson.org/key-transition-2019-03-20.txt | gpg --verify

/Simon
-----BEGIN PGP SIGNATURE-----
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=r0qK
-----END PGP SIGNATURE-----

Planning for a new OpenPGP key

I’m the process of migrating to a new OpenPGP key. I have been using GnuPG with keys stored on external hardware (smartcards) for a long time, and I’m firmly committed to that choice. Algorithm wise, RSA was the best choice back for me when I created my key in 2002, and I used it successfully with a non-standard key size for many years. In 2014 it was time for me to move to a new stronger key, and I still settled on RSA and a non-standard key size. My master key was 3744 bits instead of 1280 bits, and the smartcard subkeys were 2048 bits instead of 1024 bits. At that time, I had already moved from the OpenPGP smartcard to the NXP-based YubiKey NEO (version 3) that runs JavaCard applets. The primary relevant difference for me was the availability of source code for the OpenPGP implementation running on the device, in the ykneo-openpgp project. The device was still a proprietary hardware and firmware design though.

Five years later, it is time for a new key again, and I allow myself to revisit some decisions that I made last time.

GnuPG has supported Curve25519/Ed25519 for some time, and today I prefer it over RSA. Infrastructure has been gradually introducing support for it as well, to the point that I now believe I can cut the ropes to the old world with RSA. Having a offline master key is still a strong preference, so I will stick to that decision. You shouldn’t run around with your primary master key if it is possible to get by with subkeys for daily use, and that has worked well for me over the years.

Hardware smartcard support for Curve25519/Ed25519 has been behind software support. NIIBE Yutaka developed the FST-01 hardware device in 2011, and the more modern FST-01G device in 2016. He also wrote the Gnuk software implementation of the OpenPGP card specification that runs on the FST-01 hardware (and other devices). The FST-01 hardware design is open, and it only runs the Gnuk free software. You can buy the FST-01G device from the FSF. The device has not received the FSF Respects Your Freedom stamp, even though it is sold by FSF which seems a bit hypocritical. Hardware running Gnuk are the only free software OpenPGP smartcard that supports Curve25519/Ed25519 right now, to my knowledge. The physical form factor is not as slick as the YubiKey (especially the nano-versions of the YubiKey that can be emerged into the USB slot), but it is a trade-off I can live with. Niibe introduced the FST-01SZ at FOSDEM’19 but to me it does not appear to offer any feature over the FST-01G and is not available for online purchase right now.

I have always generated keys in software using GnuPG. My arguments traditionally was that I 1) don’t trust closed-source RSA key generation implementations, and 2) want to be able to reproduce my setup with a brand new device. With Gnuk the first argument doesn’t hold any longer. However, I still prefer to generate keys with GnuPG on a Linux-based Debian machine because that software stack is likely to receive more auditing than Gnuk. It is a delicated decision though, since GnuPG on Debian is many orders of complexity higher than the Gnuk software. My second argument is now the primary driver for this decision.

I prefer the SHA-2 family of hashes over SHA-1, and earlier had to configure GnuPG for this. Today I believe the defaults have been improved and this is no longer an issue.

Back in 2014, I had a goal of having a JPEG image embedded in my OpenPGP key. I never finished that process, and I have not been sorry for missing out on anything as a result. On the contrary, the size of the key with an embedded image woud have been even more problematic than the already large key holding 4 embedded RSA public keys in it.

To summarize, my requirements for my OpenPGP key setup in 2019 are:

  • Curve25519/Ed25519 algorithms.
  • Master key on USB stick.
  • USB stick only used on an offline computer.
  • Subkeys for daily use (signature, encryption and authentication).
  • Keys are generated in GnuPG software and imported to the smartcard.
  • Smartcard is open hardware and running free software.

Getting this setup up and running sadly requires quite some detailed work, which will be the topic of other posts… stay tuned!