feat: add openpgp workshop content

openpgp-workshop/index.md

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+# OpenPGP Workshop
+
+[important reference](img/iceberg.png)
+
+---
+
+## What is OpenPGP
+
+* OpenPGP is an open standard for encrypting and decrypting data, as well as
+creating and managing digital signatures.
+
+* It is based on the PGP (Pretty Good Privacy) protocol, which was originally
+developed by Phil Zimmermann in the 1990s.
+
+* Uses asymmetric / public key cryptography
+
+---
+
+## Implementations
+
+* GPG
+    * Gnu Privacy Guard
+    * Best known and most widely used
+    * Great starting point
+
+* There are lots of other implementations of OpenPGP:
+    * https://www.openpgp.org/software/developer/
+
+---
+
+## How Does It Work?
+
+---
+
+## Encrypt / Decrypt
+
+![Encryption vs Decryption diagram](img/encrypt-decrypt.png)
+
+---
+
+## Sign / Verify
+
+![Signing vs Verifying diagram](img/sign-verify.png)
+
+---
+
+## Diffie Helman Key Exchange
+
+![Diffie Helman Key Exchange diagram](img/diffie-helman.png)
+
+---
+
+## OpenPGP Anatomy
+
+* Many components but key ones are:
+    * Public Key
+    * Private Key
+
+---
+
+## Let's Try It!
+
+* Most OS come with GPG pre-installed (not Windows!)
+
+* `gpg --version`
+* `man gpg`
+* **THESE FOLLOWING KEYS WILL NOT BE SECURE, DO NOT USE THEM FOR ANYTHING OTHER THAN THIS EXERCISE!**
+* Generate keypair: `gpg --expert --full-gen-key`
+    * 1, 4096, Enter (3072), Enter (0), y, "Test Key", "fired.if.use@this.key", Enter (""), O, "password1"
+    * During generation, **mash input devices for added entropy**
+
+---
+
+## Test Your GPG Key
+
+* `gpg --list-keys`
+* `echo "super secret text" > test.txt && cat test.txt`
+* `gpg --encrypt --recipient <email/ID> test.txt`
+* `gpg -er <email/ID> <filename> && cat text.txt.gpg`: notice it's a binary
+    * You can use `--armor/-a` to encode it as ASCII so you can send the encrypted data as text
+* `gpg --armor -er <email/ID> test.txt && cat test.txt.asc`
+* `rm test.txt && ls`: remove original file
+* `gpg --decrypt test.txt.gpg && cat test.txt && rm test.txt`
+* `gpg --decrypt test.txt.asc && cat test.txt && rm text.txt`
+
+---
+
+## Sharing Your Public Key 🔑
+
+* `gpg --list-keys`
+* `gpg --export --armor <email/ID> > <name>.asc`
+* `gpg --import <name>.asc`
+
+* Task: pair up and exchange your keys, then encrypt data to each other
+    * Tip: you may encrypt the data to multiple people
+
+---
+
+## What's Happening Behind the Scenes
+
+* GPG generates a symmetric key (AES) and uses that to encrypt the bulk of the data
+
+* RSA/ECC is used only to encrypt the symmetric key
+
+* The encrypted data packet contains metadata about which public keys were encrypted to
+    * This can be hidden using `--hidden-recipient/-R`
+
+* Inspect packets using `gpg --list-packets <file.asc/file.gpg>`
+
+---
+
+## Verifying Signatures 📝
+
+* Go to: https://www.qubes-os.org/downloads/
+* Download:
+    * Qubes-R*.iso
+    * Cryptographic hash values
+    * Detached PGP signature
+    * Qubes release signing key
+
+* They have a guide that's worth reading: https://www.qubes-os.org/security/verifying-signatures/
+* Task: verify the signatures for the software are valid
+
+---
+
+## Solution
+
+* `gpg --import qubes-release-*`: import qubes signing key
+* `gpg --verify *.DIGESTS`: verify signature
+* `sha256sum -c Qubes-<...>.iso.DIGESTS`: verify hashes match
+
+---
+
+## Secure Key Management 🔒
+
+* You should assume your computer is compromised
+
+* How do we protect the GPG private key?
+
+    * Never expose them to an untrusted environment
+
+---
+
+## Basic: On-board generation:
+    * YubiKey offers generating keys inside of the YubiKey
+    * Cryptographic attestation keys were never exposed available: https://developers.yubico.com/PGP/Attestation.html
+    * CON: can't back up the keys
+    * PRO: simple setup
+
+---
+## Advanced - cold / virtualization
+
+* Can use `gpg` / `sq` / `keyfork`
+
+* [Hashbang GPG Guide](https://book.hashbang.sh/docs/security/key-management/gnupg/): helpful guide for GPG - good resource for beginners who want to do the advanced setup
+
+* [openpgp-card-tools](https://codeberg.org/openpgp-card/openpgp-card-tools): great for loading keys onto smart cards
+
+* Can use a variety of smart cards: NitroKey3, SoloKey, Yubikey
+    * NitroKey and SoloKey are fully open which is great for verifiability - may requires flashing firmware
+
+* [openpgp-card-tools](https://codeberg.org/openpgp-card/openpgp-card-tools) is helpful for loading the card
+
+* Airgapped system (preferred)
+
+* Virtual machine on a hypervisor via hardware virtualization (ok for some threat models)
+
+---
+
+## Backup Trick 🧙
+
+* Generate long lived keys
+
+* Load them onto smart card
+
+* Take plaintext key data and put it in a dir
+
+* Encrypt the dir to your public key
+
+* Delete keys so that only ones that remain are on smart cards (recommended to have at least 2 or 3, for redundancy)
+
+* Smart cards have a "brick" after x attempts feature
+
+---
+
+## SSH Usage
+
+* OpenPGP keys can be used for SSH as well 🪄:
+    * `gpg --export-ssh-key <email/keyID>`
+
+* Set up shell to use smart card for ssh:
+    ```
+    # always use smart card for ssh
+    unset SSH_AGENT_PID
+    if [ "${gnupg_SSH_AUTH_SOCK_by:-0}" -ne $$ ]; then
+        export SSH_AUTH_SOCK="$(gpgconf --list-dirs agent-ssh-socket)"
+    fi
+    ```
+---
+
+## Git Usage
+
+* You can sign commits using OpenPGP / GPG
+
+    ```~/.bashrc
+    GPG_TTY=$(tty)
+    export GPG_TTY
+    ```
+
+    ```~/.gitconfig
+    [user]
+        email = <email>
+        name = <name>
+        signingKey = <key_id>
+    [commit]
+        gpgSign = true
+    [merge]
+        gpgSign = true
+    [gpg]
+        program = gpg
+    ```
+
+---
+
+## Further Studies
+
+* [OpenPGP for application developers](https://openpgp.dev/book/): Deep dive on OpenPGP
+
+* [Sequoia](https://sequoia-pgp.org/): alternate OpenPGP implementation in rust
+
+* [openpgp-card](https://codeberg.org/openpgp-card)
+    * [openpgp-card-tools](https://codeberg.org/openpgp-card/openpgp-card-tools)
+    * [ssh-agent](https://codeberg.org/openpgp-card/ssh-agent)