<!--
Title: How to generate and air gap PGP private keys using GnuPG, Tails and YubiKey
Description: Learn how to generate and air gap PGP private keys using GnuPG, Tails and YubiKey.
Author: Sun Knudsen <https://github.com/sunknudsen>
Contributors: Sun Knudsen <https://github.com/sunknudsen>
Reviewers:
Publication date: 2021-07-21T15:45:10.940Z
Listed: true
-->

# How to generate and air gap PGP private keys using GnuPG, Tails and YubiKey

> Heads-up: guide inspired by https://github.com/drduh/YubiKey-Guide.

## Requirements

- [Tails USB flash drive or SD card](../how-to-install-tails-on-usb-flash-drive-or-sd-card) with VeraCrypt [installed](../how-to-install-and-use-veracrypt-on-tails)
- YubiKey with [OpenPGP](https://www.yubico.com/us/store/compare/) support (firmware version `5.2.3` or higher)
- Computer running macOS Catalina or Big Sur

## Caveats

- When copy/pasting commands that start with `$`, strip out `$` as this character is not part of the command
- When copy/pasting commands that start with `cat << "EOF"`, select all lines at once (from `cat << "EOF"` to `EOF` inclusively) as they are part of the same (single) command

## Setup guide (on Tails)

### Step 1: boot to Tails and set admin password

> Heads-up: if keyboard layout of computer isn’t “English (US)”, set “Keyboard Layout”.

Click “+” under “Additional Settings”, then “Administration Password”, set password, click “Add” and, finally, click “Start Tails”.

### Step 2: establish network connection using ethernet cable or Wi-Fi and wait for Tor to be ready

Connected to Tor successfully

👍

### Step 3: import Dennis Fokin’s and Emil Lundberg’s PGP public keys (used to verify downloads below)

> Heads-up: release may be signed by [another](https://developers.yubico.com/Software_Projects/Software_Signing.html) Yubico developer.

```console
$ gpg --keyserver hkps://keys.openpgp.org --search-keys 9E885C0302F9BB9167529C2D5CBA11E6ADC7BCD1
gpg: data source: https://keys.openpgp.org:443
(1)	Dennis Fokin <dennis.fokin@yubico.com>
	  4096 bit RSA key 0x5CBA11E6ADC7BCD1, created: 2019-09-17
Keys 1-1 of 1 for "9E885C0302F9BB9167529C2D5CBA11E6ADC7BCD1".  Enter number(s), N)ext, or Q)uit > 1
gpg: key 0x5CBA11E6ADC7BCD1: public key "Dennis Fokin <dennis.fokin@yubico.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1

$ gpg --keyserver hkps://keys.openpgp.org --search-keys 57a9deed4c6d962a923bb691816f3ed99921835e
gpg: data source: https://keys.openpgp.org:443
(1)	Emil Lundberg (Software Developer) <emil@yubico.com>
	  4096 bit RSA key 0x816F3ED99921835E, created: 2017-08-03
Keys 1-1 of 1 for "57a9deed4c6d962a923bb691816f3ed99921835e".  Enter number(s), N)ext, or Q)uit > 1
gpg: key 0x816F3ED99921835E: public key "Emil Lundberg (Software Developer) <emil@yubico.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1
```

imported: 1

👍

### Step 4: download [YubiKey Manager](https://www.yubico.com/support/download/yubikey-manager/) AppImage release and associated PGP signature

```console
$ torsocks curl -L -o ~/Downloads/yubikey-manager-qt.AppImage https://developers.yubico.com/yubikey-manager-qt/Releases/yubikey-manager-qt-latest-linux.AppImage
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   282  100   282    0     0    300      0 --:--:-- --:--:-- --:--:--   299
100 82.2M  100 82.2M    0     0   953k      0  0:01:28  0:01:28 --:--:--  629k

$ torsocks curl -L -o ~/Downloads/yubikey-manager-qt.AppImage.sig https://developers.yubico.com/yubikey-manager-qt/Releases/yubikey-manager-qt-latest-linux.AppImage.sig
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   286  100   286    0     0    318      0 --:--:-- --:--:-- --:--:--   317
100   310  100   310    0     0    262      0  0:00:01  0:00:01 --:--:--   262
```

### Step 5: verify “YubiKey Manager” AppImage release (learn how [here](../how-to-verify-pgp-digital-signatures-using-gnupg-on-macos)) and make AppImage executable

```console
$ gpg --verify ~/Downloads/yubikey-manager-qt.AppImage.sig
gpg: assuming signed data in '/home/amnesia/Downloads/yubikey-manager-qt.AppImage'
gpg: Signature made Wed 10 Nov 2021 11:11:13 AM UTC
gpg:                using RSA key D6919FBF48C484F3CB7B71CD870B88256690D8BC
gpg: Good signature from "Dennis Fokin <dennis.fokin@yubico.com>" [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: 9E88 5C03 02F9 BB91 6752  9C2D 5CBA 11E6 ADC7 BCD1
     Subkey fingerprint: D691 9FBF 48C4 84F3 CB7B  71CD 870B 8825 6690 D8BC

$ chmod +x ~/Downloads/yubikey-manager-qt.AppImage
```

Good signature

👍

### Step 6: create and source `ykman` Bash alias

```
echo 'alias ykman="$HOME/Downloads/yubikey-manager-qt.AppImage ykman"' >> ~/.bashrc
source ~/.bashrc
```

### Step 7 (optional): copy “YubiKey Manager” AppImage to “Persistent” folder (requires Tails “Personal Data” persistence feature to be enabled)

> Heads-up: once copied, one can persistently run `~/Downloads/yubikey-manager-qt.AppImage ykman` to manage YubiKeys.

```shell
cp ~/Downloads/yubikey-manager-qt.AppImage ~/Persistent/
```

### Step 8: generate master key (used to sign signing, encryption and authentication subkeys)

When asked for passphrase, create and memorize strong passphrase or use output from `gpg --gen-random --armor 0 24` (and store password in air-gapped password manager).

```console
$ gpg --expert --full-generate-key
gpg (GnuPG) 2.2.12; Copyright (C) 2018 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.

Please select what kind of key you want:
   (1) RSA and RSA (default)
   (2) DSA and Elgamal
   (3) DSA (sign only)
   (4) RSA (sign only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
   (9) ECC and ECC
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (13) Existing key
Your selection? 11

Possible actions for a ECDSA/EdDSA key: Sign Certify Authenticate
Current allowed actions: Sign Certify

   (S) Toggle the sign capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? S

Possible actions for a ECDSA/EdDSA key: Sign Certify Authenticate
Current allowed actions: Certify

   (S) Toggle the sign capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? Q
Please select which elliptic curve you want:
   (1) Curve 25519
   (3) NIST P-256
   (4) NIST P-384
   (5) NIST P-521
   (6) Brainpool P-256
   (7) Brainpool P-384
   (8) Brainpool P-512
   (9) secp256k1
Your selection? 1
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 0
Key does not expire at all
Is this correct? (y/N) y

GnuPG needs to construct a user ID to identify your key.

Real name: John Doe
Email address: john@example.net
Comment:
You selected this USER-ID:
    "John Doe <john@example.net>"

Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit? O
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
gpg: key 0xC2709D13BAB4763C marked as ultimately trusted
gpg: directory '/home/amnesia/.gnupg/openpgp-revocs.d' created
gpg: revocation certificate stored as '/home/amnesia/.gnupg/openpgp-revocs.d/C82270B62BA89271A00A6037C2709D13BAB4763C.rev'
public and secret key created and signed.

pub   ed25519/0xC2709D13BAB4763C 2021-07-21 [C]
      Key fingerprint = C822 70B6 2BA8 9271 A00A  6037 C270 9D13 BAB4 763C
uid                              John Doe <john@example.net>
```

### Step 9: set master key ID environment variable

> Heads-up: replace `0xC2709D13BAB4763C` with master key ID.

```shell
KEY_ID=0xC2709D13BAB4763C
```

### Step 10 (optional): sign master key using another master key

#### Import signing public key

> Heads-up: replace `/path/to/signing/pub.asc` with signing public key path.

```console
$ gpg --import '/path/to/signing/pub.asc'
gpg: key 0xDFCECB410CE8A745: public key "John Doe <john@example.net>" imported
gpg: Total number processed: 1
gpg:               imported: 1
```

#### Import signing private key

> Heads-up: replace `/path/to/signing/master.asc` with signing master key path.

```console
$ gpg --import /path/to/signing/master.asc
gpg: key 0xDFCECB410CE8A745: "John Doe <john@example.net>" not changed
gpg: key 0xDFCECB410CE8A745: secret key imported
gpg: Total number processed: 1
gpg:              unchanged: 1
gpg:       secret keys read: 1
gpg:   secret keys imported: 1
```

#### Sign master key

> Heads-up: replace `0xDFCECB410CE8A745` with signing master key ID.

```console
$ gpg --ask-cert-level --default-key 0xDFCECB410CE8A745 --sign-key $KEY_ID

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
[ultimate] (1). John Doe <john@example.net>

gpg: using "0xDFCECB410CE8A745" as default secret key for signing

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
 Primary key fingerprint: C822 70B6 2BA8 9271 A00A  6037 C270 9D13 BAB4 763C

     John Doe <john@example.net>

How carefully have you verified the key you are about to sign actually belongs
to the person named above?  If you don't know what to answer, enter "0".

   (0) I will not answer. (default)
   (1) I have not checked at all.
   (2) I have done casual checking.
   (3) I have done very careful checking.

Your selection? (enter '?' for more information): 3
Are you sure that you want to sign this key with your
key "John Doe <john@example.net>" (0xDFCECB410CE8A745)

I have checked this key very carefully.

Really sign? (y/N) y
```

### Step 11: create signing, encryption and authentication subkeys

```console
$ gpg --expert --edit-key $KEY_ID
gpg (GnuPG) 2.2.12; Copyright (C) 2018 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  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
[ultimate] (1). John Doe <john@example.net>

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (12) ECC (encrypt only)
  (13) Existing key
Your selection? 10
Please select which elliptic curve you want:
   (1) Curve 25519
   (3) NIST P-256
   (4) NIST P-384
   (5) NIST P-521
   (6) Brainpool P-256
   (7) Brainpool P-384
   (8) Brainpool P-512
   (9) secp256k1
Your selection? 1
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y
Key expires at Thu 21 Jul 2022 03:21:04 PM UTC
Is this correct? (y/N) y
Really create? (y/N) y
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
[ultimate] (1). John Doe <john@example.net>

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (12) ECC (encrypt only)
  (13) Existing key
Your selection? 12
Please select which elliptic curve you want:
   (1) Curve 25519
   (3) NIST P-256
   (4) NIST P-384
   (5) NIST P-521
   (6) Brainpool P-256
   (7) Brainpool P-384
   (8) Brainpool P-512
   (9) secp256k1
Your selection? 1
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y
Key expires at Thu 21 Jul 2022 03:21:25 PM UTC
Is this correct? (y/N) y
Really create? (y/N) y
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
[ultimate] (1). John Doe <john@example.net>

gpg> addkey
Please select what kind of key you want:
   (3) DSA (sign only)
   (4) RSA (sign only)
   (5) Elgamal (encrypt only)
   (6) RSA (encrypt only)
   (7) DSA (set your own capabilities)
   (8) RSA (set your own capabilities)
  (10) ECC (sign only)
  (11) ECC (set your own capabilities)
  (12) ECC (encrypt only)
  (13) Existing key
Your selection? 11

Possible actions for a ECDSA/EdDSA key: Sign Authenticate
Current allowed actions: Sign

   (S) Toggle the sign capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? S

Possible actions for a ECDSA/EdDSA key: Sign Authenticate
Current allowed actions:

   (S) Toggle the sign capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? A

Possible actions for a ECDSA/EdDSA key: Sign Authenticate
Current allowed actions: Authenticate

   (S) Toggle the sign capability
   (A) Toggle the authenticate capability
   (Q) Finished

Your selection? Q
Please select which elliptic curve you want:
   (1) Curve 25519
   (3) NIST P-256
   (4) NIST P-384
   (5) NIST P-521
   (6) Brainpool P-256
   (7) Brainpool P-384
   (8) Brainpool P-512
   (9) secp256k1
Your selection? 1
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y
Key expires at Thu 21 Jul 2022 03:21:53 PM UTC
Is this correct? (y/N) y
Really create? (y/N) y
We need to generate a lot of random bytes. It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> save
```

### Step 12: mount backup volume (formatted using exFAT)

Click “Places”, then “Home”, then backup volume (“Samsung BAR” in example below), enter admin password and, finally, click “Authenticate”.

### Step 13: set backup volume name environment variable

```shell
VOLUME_NAME="Samsung BAR"
```

### Step 14: create VeraCrypt encrypted volume (used to store master key and subkeys)

```console
$ /home/amnesia/Persistent/veracrypt --text --create "/media/amnesia/$VOLUME_NAME/tails"
Volume type:
 1) Normal
 2) Hidden
Select [1]: 1

Enter volume size (sizeK/size[M]/sizeG): 10M

Encryption Algorithm:
 1) AES
 2) Serpent
 3) Twofish
 4) Camellia
 5) Kuznyechik
 6) AES(Twofish)
 7) AES(Twofish(Serpent))
 8) Camellia(Kuznyechik)
 9) Camellia(Serpent)
 10) Kuznyechik(AES)
 11) Kuznyechik(Serpent(Camellia))
 12) Kuznyechik(Twofish)
 13) Serpent(AES)
 14) Serpent(Twofish(AES))
 15) Twofish(Serpent)
Select [1]: 7

Hash algorithm:
 1) SHA-512
 2) Whirlpool
 3) SHA-256
 4) Streebog
Select [1]: 1

Filesystem:
 1) None
 2) FAT
 3) Linux Ext2
 4) Linux Ext3
 5) Linux Ext4
 6) NTFS
 7) exFAT
 8) Btrfs
Select [2]: 5

Enter password:
Re-enter password:

Enter PIM:

Enter keyfile path [none]:

Please type at least 320 randomly chosen characters and then press Enter:


Done: 100.000%  Speed: 2.7 MiB/s  Left: 0 s

The VeraCrypt volume has been successfully created.
```

The VeraCrypt volume has been successfully created.

👍

### Step 15: mount VeraCrypt encrypted volume

Click “Applications”, then “Utilities”, then “Unlock VeraCrypt Volumes”, then “Add”, select “tails” file on backup volume, click “Open”, enter password and, finally, click “Unlock”.

### Step 16: rename VeraCrypt encrypted volume

> Heads-up: replace `tcrypt-1793` with directory found using `ls /dev/mapper` and ignore dirty bit is set error.

```console
$ ls /dev/mapper
control  TailsData_unlocked  tcrypt-1793  tcrypt-1793_1  tcrypt-1793_2

$ sudo e2label /dev/mapper/tcrypt-1793 Tails
[sudo] password for amnesia:
```

### Step 17: set VeraCrypt encrypted volume name environment variable

> Heads-up: replace `8ff4dedf-6aa1-4b97-909d-63075b3eb70a` with directory found using `ls /media/amnesia`.

```console
$ ls /media/amnesia
8ff4dedf-6aa1-4b97-909d-63075b3eb70a

$ ENCRYPTED_VOLUME_NAME="8ff4dedf-6aa1-4b97-909d-63075b3eb70a"
```

### Step 18: change owner of VeraCrypt encrypted volume

```shell
sudo chown amnesia:amnesia /media/amnesia/$ENCRYPTED_VOLUME_NAME
```

### Step 19: export master key, subkeys and public key to VeraCrypt encrypted volume

```console
$ gpg --armor --export-secret-keys $KEY_ID > /media/amnesia/$ENCRYPTED_VOLUME_NAME/master.asc

$ gpg --armor --export-secret-subkeys $KEY_ID > /media/amnesia/$ENCRYPTED_VOLUME_NAME/sub.asc

$ gpg --armor --export $KEY_ID > /media/amnesia/$ENCRYPTED_VOLUME_NAME/pub.asc
```

### Step 20: copy public key to backup volume

> Heads-up: replace `johndoe` with name associated to master key.

```shell
cp /media/amnesia/$ENCRYPTED_VOLUME_NAME/pub.asc "/media/amnesia/$VOLUME_NAME/johndoe.asc"
```

### Step 21: dismount VeraCrypt encrypted volume

Click “Applications”, then “Utilities”, then “Unlock VeraCrypt Volumes” and, finally, click “x”.

### Step 22: back up `tails` file

> Heads-up: files stored in `tails` include private keys which, if lost, results in loosing one’s cryptographic identity (safeguard backup mindfully).

> Heads-up: one should never unlock `tails` on macOS (or any other computer that isn’t air-gapped and hardened).

### Step 23: insert and provision YubiKey

> Heads-up: default user PIN is `123456` and default admin PIN is `12345678`.

> Heads-up: one should set different PIN for user vs admin and never use admin PIN on macOS (or any other computer that isn’t air-gapped and hardened).

```console
$ gpg --card-edit

Reader ...........: 1050:0404:X:0
Application ID ...: D*******************************
Version ..........: 3.4
Manufacturer .....: Yubico
Serial number ....: 1*******
Name of cardholder: [not set]
Language prefs ...: [not set]
Sex ..............: unspecified
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: not forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 0 3
Signature counter : 0
KDF setting ......: on
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> admin
Admin commands are allowed

gpg/card> passwd
gpg: OpenPGP card no. D******************************* detected

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

Your selection? 1
PIN changed.

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: Doe
Cardholder's given name: John

gpg/card> lang
Language preferences: en

gpg/card> login
Login data (account name): john@example.net

gpg/card> list

Reader ...........: 1050:0404:X:0
Application ID ...: D*******************************
Version ..........: 3.4
Manufacturer .....: Yubico
Serial number ....: 1*******
Name of cardholder: John Doe
Language prefs ...: en
Sex ..............: unspecified
URL of public key : [not set]
Login data .......: john@example.net
Signature PIN ....: not forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 0 3
Signature counter : 0
KDF setting ......: on
Signature key ....: [none]
Encryption key....: [none]
Authentication key: [none]
General key info..: [none]

gpg/card> quit
```

### Step 24: move signing, encryption and authentication subkeys to YubiKey

```console
$ gpg --edit-key $KEY_ID
gpg (GnuPG) 2.2.12; Copyright (C) 2018 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  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> key 1

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb* ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

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

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb* ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> key 1

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> key 2

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb* cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

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

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb* cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> key 2

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> key 3

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb* ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

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

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: ultimate      validity: ultimate
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb* ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ultimate] (1). John Doe <john@example.net>

gpg> save
```

### Step 25: require YubiKey user interaction for signing, encryption and authentication operations

```console
$ ykman openpgp keys set-touch sig on --force
Enter Admin PIN:

$ ykman openpgp keys set-touch enc on --force
Enter Admin PIN:

$ ykman openpgp keys set-touch aut on --force
Enter Admin PIN:

$ ykman openpgp keys set-touch att on --force
Enter Admin PIN:

$ ykman openpgp info
OpenPGP version: 3.4
Application version: 5.4.3

PIN tries remaining: 3
Reset code tries remaining: 0
Admin PIN tries remaining: 3

Touch policies
Signature key           On
Encryption key          On
Authentication key      On
Attestation key         On
```

On

👍

### Step 26 (optional): disable all YubiKey interfaces except for OpenPGP over USB

> Heads-up: increase `sleep` delay if “Error: No YubiKey detected!” error is thrown.

```console
$ ykman config usb --disable FIDO2 --disable HSMAUTH --disable OATH --disable OTP --disable PIV --disable U2F --enable OPENPGP --force

$ ykman config nfc --disable-all --force
```

### Step 27 (optional): enable YubiKey configuration lock

> Heads-up: configuration lock prevents configuring YubiKey without entering lock code (store lock code in air-gapped password manager).

```console
$ ykman config set-lock-code --generate
Using a randomly generated lock code: cce9181f4a97bac00459419986510d40
Lock configuration with this lock code? [y/N]: y
```

### Step 28: shutdown computer

👍

---

## Subkeys expiry date extension guide (on Tails)

### Step 1: boot to Tails and set admin password

> Heads-up: if keyboard layout of computer isn’t “English (US)”, set “Keyboard Layout”.

Click “+” under “Additional Settings”, then “Administration Password”, set password, click “Add” and, finally, click “Start Tails”.

### Step 2: mount backup volume (formatted using exFAT)

Click “Places”, then “Home”, then backup volume (“Samsung BAR” in example below), enter admin password and, finally, click “Authenticate”.

### Step 3: mount VeraCrypt encrypted volume

Click “Applications”, then “Utilities”, then “Unlock VeraCrypt Volumes”, then “Add”, select “tails” file on backup volume, click “Open”, enter password and, finally, click “Unlock”.

### Step 4: import master key

```console
$ gpg --import /media/amnesia/Tails/master.asc
gpg: key 0xC2709D13BAB4763C: 1 signature not checked due to a missing key
gpg: key 0xC2709D13BAB4763C: public key "John Doe <john@example.net>" imported
gpg: key 0xC2709D13BAB4763C: secret key imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg:       secret keys read: 1
gpg:   secret keys imported: 1
gpg: no ultimately trusted keys found
```

### Step 5: set master key ID environment variable

```shell
KEY_ID=0xC2709D13BAB4763C
```

### Step 6: extend expiry date of signing, encryption and authentication subkeys

```console
$ gpg --edit-key $KEY_ID
gpg (GnuPG) 2.2.12; Copyright (C) 2018 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  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: unknown       validity: unknown
ssb  ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ unknown] (1). John Doe <john@example.net>

gpg> key 1

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: unknown       validity: unknown
ssb* ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb  cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ unknown] (1). John Doe <john@example.net>

gpg> key 2

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: unknown       validity: unknown
ssb* ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb* cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb  ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ unknown] (1). John Doe <john@example.net>

gpg> key 3

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: unknown       validity: unknown
ssb* ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb* cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb* ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ unknown] (1). John Doe <john@example.net>

gpg> expire
Are you sure you want to change the expiration time for multiple subkeys? (y/N) y
Please specify how long the key should be valid.
         0 = key does not expire
      <n>  = key expires in n days
      <n>w = key expires in n weeks
      <n>m = key expires in n months
      <n>y = key expires in n years
Key is valid for? (0) 1y
Key expires at Thu 21 Jul 2022 03:32:11 PM UTC
Is this correct? (y/N) y

sec  ed25519/0xC2709D13BAB4763C
     created: 2021-07-21  expires: never       usage: C
     trust: unknown       validity: unknown
ssb* ed25519/0x02EDC61B6543509B
     created: 2021-07-21  expires: 2022-07-21  usage: S
ssb* cv25519/0xD4634E0D6E2DD8BF
     created: 2021-07-21  expires: 2022-07-21  usage: E
ssb* ed25519/0x1E7B69B238FFA21B
     created: 2021-07-21  expires: 2022-07-21  usage: A
[ unknown] (1). John Doe <john@example.net>

gpg> save
```

### Step 7: export public key to VeraCrypt encrypted volume

```console
$ gpg --armor --export $KEY_ID > /media/amnesia/Tails/pub.asc
```

### Step 8: copy public key to backup volume

> Heads-up: replace `Samsung BAR` with backup volume name and `johndoe` with name associated to master key.

```shell
cp /media/amnesia/Tails/pub.asc "/media/amnesia/Samsung BAR/johndoe.asc"
```

### Step 9: dismount VeraCrypt encrypted volume

Click “Applications”, then “Utilities”, then “Unlock VeraCrypt Volumes” and, finally, click “x”.

### Step 10: shutdown computer

👍

---

## Usage guide (on macOS)

### Step 1: install [Homebrew](https://brew.sh/)

```console
$ /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

$ uname -m | grep arm64 && echo 'export PATH=$PATH:/opt/homebrew/bin' >> ~/.zshrc && source ~/.zshrc
```

### Step 2: disable Homebrew analytics

```shell
brew analytics off
```

### Step 3: install [GnuPG](https://gnupg.org/) and [pinentry-mac](https://github.com/GPGTools/pinentry)

```shell
brew install gnupg pinentry-mac
```

### Step 4: import public key

> Heads-up: replace `Samsung BAR` with backup volume name and `johndoe` with name associated to master key.

```console
$ gpg --keyid-format 0xlong --import "/Volumes/Samsung BAR/johndoe.asc"
gpg: directory '/Users/sunknudsen/.gnupg' created
gpg: keybox '/Users/sunknudsen/.gnupg/pubring.kbx' created
gpg: key 0xC2709D13BAB4763C: 1 signature not checked due to a missing key
gpg: /Users/sunknudsen/.gnupg/trustdb.gpg: trustdb created
gpg: key 0xC2709D13BAB4763C: public key "John Doe <john@example.net>" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: no ultimately trusted keys found
```

### Step 5: insert YubiKey and import private key stubs

```console
$ gpg --keyid-format 0xlong --card-status
Reader ...........: Yubico YubiKey CCID
Application ID ...: D*******************************
Application type .: OpenPGP
Version ..........: 0.0
Manufacturer .....: Yubico
Serial number ....: 1*******
Name of cardholder: John Doe
Language prefs ...: en
Salutation .......:
URL of public key : [not set]
Login data .......: john@example.net
Signature PIN ....: not forced
Key attributes ...: ed25519 cv25519 ed25519
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 0 3
Signature counter : 0
KDF setting ......: off
UIF setting ......: Sign=on Decrypt=on Auth=on
Signature key ....: ACE1 3F15 90C1 A8C9 D942  51E3 02ED C61B 6543 509B
      created ....: 2021-07-21 18:44:34
Encryption key....: 0524 00F4 8E1D 085A F3E1  61EC D463 4E0D 6E2D D8BF
      created ....: 2021-07-21 18:44:52
Authentication key: A27B 582F 1F62 03BA 549B  3D44 1E7B 69B2 38FF A21B
      created ....: 2021-07-21 18:45:13
General key info..: sub  ed25519/0x02EDC61B6543509B 2021-07-21 John Doe <john@example.net>
sec#  ed25519/0xC2709D13BAB4763C  created: 2021-07-21  expires: never
ssb>  ed25519/0x02EDC61B6543509B  created: 2021-07-21  expires: 2022-07-21
                                  card-no: 0006 1*******
ssb>  cv25519/0xD4634E0D6E2DD8BF  created: 2021-07-21  expires: 2022-07-21
                                  card-no: 0006 1*******
ssb>  ed25519/0x1E7B69B238FFA21B  created: 2021-07-21  expires: 2022-07-21
                                  card-no: 0006 1*******
```

👍

### Step 6: set master key ID environment variable

> Heads-up: replace `0xC2709D13BAB4763C` with master key ID.

```shell
KEY_ID=0xC2709D13BAB4763C
```

### Step 7: configure GnuPG

#### Create or override `dirmngr.conf`

Heads-up: back up current config using `cp ~/.gnupg/dirmngr.conf ~/.gnupg/dirmngr.conf.backup` (if necessary).

```shell
cat << "EOF" > ~/.gnupg/dirmngr.conf
disable-ipv6
keyserver hkps://keys.openpgp.org
EOF
```

#### Create or override `gpg.conf`

Heads-up: back up current config using `cp ~/.gnupg/gpg.conf ~/.gnupg/gpg.conf.backup` (if necessary).

```shell
cat << EOF > ~/.gnupg/gpg.conf
cert-digest-algo SHA512
charset utf-8
default-key $KEY_ID
default-preference-list SHA512 SHA384 SHA256 AES256 AES192 AES ZLIB BZIP2 ZIP Uncompressed
fixed-list-mode
keyid-format 0xlong
keyserver hkps://keys.openpgp.org
list-options show-uid-validity
no-comments
no-emit-version
no-symkey-cache
personal-cipher-preferences AES256 AES192 AES
personal-compress-preferences ZLIB BZIP2 ZIP Uncompressed
personal-digest-preferences SHA512 SHA384 SHA256
require-cross-certification
s2k-cipher-algo AES256
s2k-digest-algo SHA512
throw-keyids
use-agent
verify-options show-uid-validity
with-fingerprint
EOF
```

#### Back up and overwrite `gpg-agent.conf`

Heads-up: back up current config using `cp ~/.gnupg/gpg-agent.conf ~/.gnupg/gpg-agent.conf.backup` (if necessary).

```shell
cat << EOF > ~/.gnupg/gpg-agent.conf
default-cache-ttl 60
default-cache-ttl-ssh 60
enable-ssh-support
max-cache-ttl 120
max-cache-ttl-ssh 120
pinentry-program $(brew --prefix)/bin/pinentry-mac
EOF
```

### Step 8: configure shell

```shell
cat << "EOF" >> ~/.zshrc
export GPG_TTY="$(tty)"
export SSH_AUTH_SOCK=$(gpgconf --list-dirs agent-ssh-socket)
gpgconf --launch gpg-agent
gpg-connect-agent UPDATESTARTUPTTY /bye > /dev/null
EOF
source ~/.zshrc
```

### Step 9: generate SSH public key

> Heads-up: replace `john@example.net` with email and `johndoe` with name associated to master key.

```console
$ mkdir -p ~/.ssh

$ ssh-add -L | awk  '{print $1 " " $2 " john@example.net"}' | tee ~/.ssh/johndoe.pub
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJ62kuKCXcufbvQeXS8h5D6PW233AMBXHzKpXO0EhmJ6 john@example.net
```

ssh-ed25519 AAAAC3Nz… john@example.net

👍

### Step 10: reload `gpg-agent` (required to enable `pinentry-mac`)

```console
$ gpgconf --kill gpg-agent

$ gpgconf --launch gpg-agent

$ gpg-connect-agent UPDATESTARTUPTTY /bye
OK
```

OK

👍

### Step 11 (optional): enable Git [signing](https://git-scm.com/book/en/v2/Git-Tools-Signing-Your-Work)

```shell
git config --global commit.gpgsign true
git config --global gpg.program $(which gpg)
git config --global user.signingkey $KEY_ID
```

### Step 12 (optional): publish public key to hkps://keys.openpgp.org

```console
$ gpg --send-keys $KEY_ID
gpg: sending key 0xC2709D13BAB4763C to hkps://keys.openpgp.org
```

gpg: sending key 0xC2709D13BAB4763C to hkps://keys.openpgp.org

👍