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@ -2,7 +2,7 @@ This is a guide to using [YubiKey](https://www.yubico.com/products/yubikey-hardw
Keys stored on YubiKey are [non-exportable](http://web.archive.org/web/20201125172759/https://support.yubico.com/hc/en-us/articles/360016614880-Can-I-Duplicate-or-Back-Up-a-YubiKey-) (as opposed to file-based keys that are stored on disk) and are convenient for everyday use. Instead of having to remember and enter passphrases to unlock SSH/GPG keys, YubiKey needs only a physical touch after being unlocked with a PIN. All signing and encryption operations happen on the card, rather than in OS memory. Keys stored on YubiKey are [non-exportable](http://web.archive.org/web/20201125172759/https://support.yubico.com/hc/en-us/articles/360016614880-Can-I-Duplicate-or-Back-Up-a-YubiKey-) (as opposed to file-based keys that are stored on disk) and are convenient for everyday use. Instead of having to remember and enter passphrases to unlock SSH/GPG keys, YubiKey needs only a physical touch after being unlocked with a PIN. All signing and encryption operations happen on the card, rather than in OS memory.
**New!** [drduh/Purse](https://github.com/drduh/Purse) is a password manager which uses GPG and YubiKey. **Tip** [drduh/Purse](https://github.com/drduh/Purse) is a password manager which uses GPG and YubiKey to securely store and read credentials.
> **Security Note**: If you followed this guide before Jan 2021, your GPG *PIN* and *Admin PIN* may be set to their default values (`123456` and `12345678` respectively). This would allow an attacker to use your Yubikey or reset your PIN. Please see the [Change PIN](#change-pin) section for details on how to change your PINs. > **Security Note**: If you followed this guide before Jan 2021, your GPG *PIN* and *Admin PIN* may be set to their default values (`123456` and `12345678` respectively). This would allow an attacker to use your Yubikey or reset your PIN. Please see the [Change PIN](#change-pin) section for details on how to change your PINs.
@ -30,7 +30,6 @@ If you have a comment or suggestion, please open an [Issue](https://github.com/d
* [Encryption](#encryption) * [Encryption](#encryption)
* [Authentication](#authentication) * [Authentication](#authentication)
* [Add extra identities](#add-extra-identities) * [Add extra identities](#add-extra-identities)
- [Create keys with --batch and --quick-add-key](#create-keys-with---batch-and---quick-add-keys)
- [Verify](#verify) - [Verify](#verify)
- [Export secret keys](#export-secret-keys) - [Export secret keys](#export-secret-keys)
- [Revocation certificate](#revocation-certificate) - [Revocation certificate](#revocation-certificate)
@ -86,6 +85,7 @@ If you have a comment or suggestion, please open an [Issue](https://github.com/d
- [Notes](#notes) - [Notes](#notes)
- [Troubleshooting](#troubleshooting) - [Troubleshooting](#troubleshooting)
- [Alternatives](#alternatives) - [Alternatives](#alternatives)
* [Create keys with batch](#create-keys-with-batch)
- [Links](#links) - [Links](#links)
@ -470,33 +470,27 @@ You may also need more recent versions of [yubikey-personalization](https://deve
Generating cryptographic keys requires high-quality [randomness](https://www.random.org/randomness/), measured as entropy. Generating cryptographic keys requires high-quality [randomness](https://www.random.org/randomness/), measured as entropy.
Most operating systems use software-based pseudorandom number generators. On newer machines there are CPU based hardware random number generators (HRNG) or you can use a separate hardware device like the White Noise or [OneRNG](https://onerng.info/onerng/) will [increase the speed](https://lwn.net/Articles/648550/) of entropy generation and possibly the quality. Most operating systems use software-based pseudorandom number generators or CPU-based hardware random number generators (HRNG).
YubiKey firmware version 5.2.3 introduced "Enhancements to OpenPGP 3.4 Support" - which can optionally gather additional entropy from YubiKey via the SmartCard interface. Optionally, you can use a separate hardware device like [OneRNG](https://onerng.info/onerng/) to [increase the speed](https://lwn.net/Articles/648550/) of entropy generation and possibly also the quality.
## YubiKey ## YubiKey
To feed the system's PRNG with entropy generated by the YubiKey itself, issue: YubiKey firmware version 5.2.3 introduced "Enhancements to OpenPGP 3.4 Support" - which can optionally gather additional entropy from YubiKey via the SmartCard interface.
To seed the kernel's PRNG with additional 512 bytes retrieved from the YubiKey:
```console ```console
$ echo "SCD RANDOM 512" | gpg-connect-agent | sudo tee /dev/random | hexdump -C $ echo "SCD RANDOM 512" | gpg-connect-agent | sudo tee /dev/random | hexdump -C
``` ```
This will seed the Linux kernel's PRNG with additional 512 bytes retrieved from the YubiKey.
## OneRNG ## OneRNG
Install [rng-tools](https://wiki.archlinux.org/index.php/Rng-tools) software: Install [rng-tools](https://wiki.archlinux.org/index.php/Rng-tools) software:
```console ```console
$ sudo apt -y install at rng-tools python3-gnupg openssl $ sudo apt -y install at rng-tools python3-gnupg openssl
```
If you have a hardware device other than the CPU based one, install the accompany software and point rng-tools to its `/dev/` device.
OneRNG specific example:
```
$ wget https://github.com/OneRNG/onerng.github.io/raw/master/sw/onerng_3.7-1_all.deb $ wget https://github.com/OneRNG/onerng.github.io/raw/master/sw/onerng_3.7-1_all.deb
$ sha256sum onerng_3.7-1_all.deb $ sha256sum onerng_3.7-1_all.deb
@ -577,7 +571,7 @@ $ gpg --gen-random --armor 0 24
ydOmByxmDe63u7gqx2XI9eDgpvJwibNH ydOmByxmDe63u7gqx2XI9eDgpvJwibNH
``` ```
Use upper case letters for improved readability if they are written down: Use upper case letters for improved readability if passwords are written down by hand:
```console ```console
$ LC_ALL=C tr -dc '[:upper:]' < /dev/urandom | fold -w 20 | head -n1 $ LC_ALL=C tr -dc '[:upper:]' < /dev/urandom | fold -w 20 | head -n1
@ -1010,77 +1004,6 @@ gpg> save
By default, the last identity added will be the primary user ID - use `primary` to change that. By default, the last identity added will be the primary user ID - use `primary` to change that.
# Create keys with `--batch` and `--quick-add-keys`
To remove some complexity from the process, we will show an alternate procedure to generate the keys using template files and the `--batch` parameter. For futher details, full GNUPG documentation can be found [at this link](https://www.gnupg.org/documentation/manuals/gnupg/Unattended-GPG-key-generation.html). This procedure will have just the same result as described above.
For your convenience you can start from this RSA4096 key template: [gen-params-rsa4096](contrib/gen-params-rsa4096). If you're using GnuPG v2.1.7 or newer we strongly recommend generating ED25519 keys ([gen-params-ed25519](contrib/gen-params-ed25519), the procedure is the same). These templates will not set the master key to expire - see [Note #3](#notes).
Generate a RSA4096 master key:
```console
$ gpg --batch --generate-key gen-params-rsa4096
gpg: Generating a basic OpenPGP key
gpg: key 0xEA5DE91459B80592 marked as ultimately trusted
gpg: revocation certificate stored as '/tmp.FLZC0xcM/openpgp-revocs.d/D6F924841F78D62C65ABB9588B461860159FFB7B.rev'
gpg: done
```
Let's check the result:
```console
$ gpg --list-key
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
/tmp.FLZC0xcM/pubring.kbx
-------------------------------
pub rsa4096/0xFF3E7D88647EBCDB 2021-08-22 [C]
Key fingerprint = 011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB
uid [ultimate] Dr Duh <doc@duh.to>
```
The key fingerprint (`011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB`) will be used to create the three subkeys for signing, authentication and encryption.
Now create the three subkeys for signing, authentication and encryption. Use a 1 year expiration for sub-keys - they can be renewed using the offline master key, see [rotating keys](#rotating-keys).
We will use the the quick key manipulation interface of GNUPG (with `--quick-add-key`), see [the documentation](https://www.gnupg.org/documentation/manuals/gnupg/Unattended-GPG-key-generation.html#Unattended-GPG-key-generation).
Create a [signing subkey](https://stackoverflow.com/questions/5421107/can-rsa-be-both-used-as-encryption-and-signature/5432623#5432623):
```console
$ gpg --quick-add-key "011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB" \
rsa4096 sign 1y
```
Now create an [encryption subkey](https://www.cs.cornell.edu/courses/cs5430/2015sp/notes/rsa_sign_vs_dec.php):
```console
$ gpg --quick-add-key "011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB" \
rsa4096 encrypt 1y
```
Finally, create an [authentication subkey](https://superuser.com/questions/390265/what-is-a-gpg-with-authenticate-capability-used-for):
```console
$ gpg --quick-add-key "011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB" \
rsa4096 auth 1y
```
Let's check the final result:
```console
$ gpg --list-keys
/tmp.FLZC0xcM/pubring.kbx
-------------------------------
pub rsa4096/0xFF3E7D88647EBCDB 2021-08-22 [C]
Key fingerprint = 011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB
uid [ultimate] Dr Duh <doc@duh.to>
sub rsa4096/0xBECFA3C1AE191D15 2017-10-09 [S] [expires: 2018-10-09]
sub rsa4096/0x5912A795E90DD2CF 2017-10-09 [E] [expires: 2018-10-09]
sub rsa4096/0x3F29127E79649A3D 2017-10-09 [A] [expires: 2018-10-09]
```
# Verify # Verify
List the generated secret keys and verify the output: List the generated secret keys and verify the output:
@ -1727,7 +1650,7 @@ $ cp -avi /mnt/encrypted-storage/tmp.XXX $GNUPGHOME
$ cd $GNUPGHOME $ cd $GNUPGHOME
``` ```
## Switching between two or more Yubikeys. ## Switching between two or more Yubikeys
When you add a GPG key to a Yubikey using the *keytocard* command, GPG deletes the key from your keyring and adds a *stub* pointing to that exact Yubikey (the stub identifies the GPG KeyID and the Yubikey's serial number). When you add a GPG key to a Yubikey using the *keytocard* command, GPG deletes the key from your keyring and adds a *stub* pointing to that exact Yubikey (the stub identifies the GPG KeyID and the Yubikey's serial number).
@ -1861,7 +1784,7 @@ sub 4096R/0x3F29127E79649A3D created: 2017-10-09 expires: 2018-10-09 usage:
gpg> quit gpg> quit
``` ```
Remove and re-insert YubiKey and check the status: Remove and re-insert YubiKey and verify the status:
```console ```console
$ gpg --card-status $ gpg --card-status
@ -2942,6 +2865,64 @@ Before you unmount your backup, ask yourself if you should make another one just
* [`piv-agent`](https://github.com/smlx/piv-agent) is an SSH and GPG agent which you can use with your PIV hardware security device (e.g. a Yubikey). * [`piv-agent`](https://github.com/smlx/piv-agent) is an SSH and GPG agent which you can use with your PIV hardware security device (e.g. a Yubikey).
* [`keytotpm`](https://www.gnupg.org/documentation/manuals/gnupg/OpenPGP-Key-Management.html) is an option to use GnuPG with TPM systems. * [`keytotpm`](https://www.gnupg.org/documentation/manuals/gnupg/OpenPGP-Key-Management.html) is an option to use GnuPG with TPM systems.
## Create keys with batch
Keys can also be generated using template files and the `--batch` parameter - see [GnuPG documentation](https://www.gnupg.org/documentation/manuals/gnupg/Unattended-GPG-key-generation.html)
Start from the [gen-params-rsa4096](contrib/gen-params-rsa4096) template. If you're using GnuPG v2.1.7 or newer, you can also use the ([gen-params-ed25519](contrib/gen-params-ed25519) template. These templates will not set the master key to expire - see [Note #3](#notes).
Generate master key:
```console
$ gpg --batch --generate-key gen-params-rsa4096
gpg: Generating a basic OpenPGP key
gpg: key 0xEA5DE91459B80592 marked as ultimately trusted
gpg: revocation certificate stored as '/tmp.FLZC0xcM/openpgp-revocs.d/D6F924841F78D62C65ABB9588B461860159FFB7B.rev'
gpg: done
```
Verify the result:
```console
$ gpg --list-key
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
/tmp.FLZC0xcM/pubring.kbx
-------------------------------
pub rsa4096/0xFF3E7D88647EBCDB 2021-08-22 [C]
Key fingerprint = 011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB
uid [ultimate] Dr Duh <doc@duh.to>
```
The key fingerprint (`011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB`) will be used to create the three subkeys for signing, authentication and encryption.
Now create the three subkeys for signing, authentication and encryption. Use a 1 year expiration for sub-keys - they can be renewed using the offline master key, see [rotating keys](#rotating-keys).
We will use the the quick key manipulation interface of GNUPG (with `--quick-add-key`), see [the documentation](https://www.gnupg.org/documentation/manuals/gnupg/Unattended-GPG-key-generation.html#Unattended-GPG-key-generation).
Create a [signing subkey](https://stackoverflow.com/questions/5421107/can-rsa-be-both-used-as-encryption-and-signature/5432623#5432623):
```console
$ gpg --quick-add-key "011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB" \
rsa4096 sign 1y
```
Now create an [encryption subkey](https://www.cs.cornell.edu/courses/cs5430/2015sp/notes/rsa_sign_vs_dec.php):
```console
$ gpg --quick-add-key "011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB" \
rsa4096 encrypt 1y
```
Finally, create an [authentication subkey](https://superuser.com/questions/390265/what-is-a-gpg-with-authenticate-capability-used-for):
```console
$ gpg --quick-add-key "011C E16B D45B 27A5 5BA8 776D FF3E 7D88 647E BCDB" \
rsa4096 auth 1y
```
# Links # Links
* https://alexcabal.com/creating-the-perfect-gpg-keypair/ * https://alexcabal.com/creating-the-perfect-gpg-keypair/