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Yubikey Generate Key On Card Template

⚠️ Content below I now consider obsolete. My latest guide is now located here: Technical guide for using YubiKey series 4 for GPG and SSH. Please consult that resource instead.

We will generate a master key with only the Certify capability and three subkeys with each of the Sign, Encrypt and Authenticate capabilities. These latter three keys are meant for daily use and will be transferred to an OpenPGP smartcard, which has three corresponding slots. The master private key can then be moved to offline cold storage, or stored on a second smartcard.

We are generating keys on a secure computer instead of on the card, because it allows more flexibility. Ideally this means a machine running Tails or one that is air-gapped and not connected to the internet.

The Certificates dialog provides a Generate new key button to start this process. Each slot is represented as a tab in the dialog, and each tab has its own button to generate a key. You will need to specify the algorithm for the key, and the output format. The private key will be generated on the YubiKey, and will never leave the device. Jun 17, 2019 You can do this by running gpg -card-edit and typing admin and then help to list available commands. Use passwd to change your PINs. You can also toggle the forcesig flag to control whether you'd like to require a PIN to be entered every time you sign a message. Generate the master key $ gpg -expert -gen-key Select 8: RSA (set your own. Jan 14, 2017 By Paul Wagenseil 14 January 2017 It's not hard to cheaply make your own two-factor authentication USB key, a researcher showed at the ShmooCon hacker conference.

This guide assumes that if you want to sign other peoples keys, then you will require the aforementioned secondary smartcard with your master key stored in its Signature slot, or if you only have one smartcard, then you'll have to fetch the master key out of cold storage. By default, GPG generates a master key with the Certify and Sign capabilities and a subkey with the Encrypt capability. We will override this using expert mode.

First, make sure you're running GnuPG 2.x. This is important because you can't use 4096-bit RSA keys on most smartcards with GnuPG 1.x. A Bash alias will suffice, i.e.alias gpg=gpg2.

If you use the Enigmail Thunderbird add-on, make sure the GPG path to /usr/bin/gpg2.

If you're using a YubiKey on Tails, you might need to add udev rules in order to interact with the device. Create a file named 70-yubikey.rules in /etc/udev/rules.d with the following contents:

Then run sudo udevadm control --reload-rules.

For the sake of brevity, this guide assumes that you will always enter passphrases and PINs, and answer Yes by typing y when prompted.

At some point either before or after you should initialize your new smartcard, setting some of the variables if you so choose (stuff like name, url, login, lang, sex), but most importantly modify the default PIN (123456) and admin PIN (12345678). You can do this by running gpg --card-edit and typing admin and then help to list available commands. Use passwd to change your PINs. You can also toggle the forcesig flag to control whether you'd like to require a PIN to be entered every time you sign a message.

Generate the master key

Select 8: RSA (set your own capabilities)

Select S, E, and Q so that you're left with only the Certify capability.

Set a 4096 bit key size.

Set the expiration date.

Setup a UID.

Setup a passphrase.

The key is generated.

Add UIDs

Use gpg> adduid to add as many UIDs or e-mail addresses as you need. Once you're done, toggle to gpg> uid <#> and use the gpg> primary command to set the primary UID.

Now we will add subkeys for each capability to be transferred to the main smartcard designated for daily use.

Create the Sign key

Select 4: RSA (sign only).

Set a 4096 bit key size.

Set the expiration date.

The key is generated.

Create the Encrypt key

Select 6: RSA (encrypt only).

Set a 4096 bit key size.

Set the expiration date.

The key is generated.

Create the Authenticate key

Select 8: RSA (set your own capabilities)

Select S and E to toggle off the Sign and Encrypt capabilities.

Select A to toggle on the Authenticate capability and press Q.

Set a 4096 bit key size.

Set the expiration date.

The key is generated.

Set trust level

By the way, you should probably set the public key to the ultimate trust level.

Select 5 = I trust ultimately.

Add signatures

If you want to sign the new master key with your previous key that you're transitioning from, the time is now.

Generate revocation certificate

While you still have access to the master key with the Certify capability, it's a good idea to create a revocation certificate.

Backup everything

You can move these private keys plus the revocation certificate someplace safe, like an encrypted partition or offline storage media.

Transfer your master key to a secondary smartcard

If you have two smartcards available, then you can store your master key in the Signature slot of a second smartcard, and use this one for stuff like signing other peoples keys, and making changes to your key, as in the scheme recommended by Tom Lowenthal's guide. After initializing the card and setting new PINs:

gpg> toggle

gpg> keytocard

Answer 'y' to 'Really move the primary key?'

Select 1: Signature key.

gpg> save

As mentioned, switching to this smartcard will be required whenever you want to sign somebody else's key or make modifications to your key. Now eject it and put it away somewhere. You may want to create a label so you can tell them apart. Insert the primary smartcard that you've selected for daily use.

Load subkeys onto the smartcard

You can use gpg --card-edit to initialize your smartcard: set the PINs, and variables like language, sex, your first and last name, or a URL for downloading your key. Now let's load the keys onto it.

Select 1: Signature key.

Un-toggle key one:gpg> key 1

Toggle key two:gpg> key 2

Select 2: Encryption key.

Un-toggle key two: gpg> key 2

Toggle key three: gpg> key 3

Select 3: Authentication key.

Now what?

You shouldn't have to delete any secret keys, as they were moved to the smartcard. When you use either keytocard command or perform key generation on the card, GnuPG places a 'stub' in your keyring so that it knows the actual secret key material is located on the smartcard. It looks like you have the secret key on your computer but you actually don't, and you can't decrypt anything without the card. It's just a stub pointing to the smartcard — which is something you do want to keep if you'd like this to be usable.

So what if you deleted the secret keys anyway and lost the stubs? Just run $ gpg --card-status or open the 'Manage Smartcard' menu in Enigmail in order to instantly re-associate and populate your keyring with the information from your smartcard. However, always keep in mind that you need the corresponding public key in your keyring to work with the smartcard on whatever computer you're using.

After you purposely delete the secret key stubs from your keyring (otherwise it will say the keys are already associated with another card), you can even put these same keys on a different smartcard by repeating part of the process above.

However, you should probably backup or transfer these stubs to your regular computer first, since they're pointing to separate smartcards for different subkeys, and it's very difficult to re-create if you lose them—but it can be done using a tool called gpgsplit. Withou

Yubikey Generate Key On Card