gpg --help

gpg --gen-key

# List public keys you have stored (yours and other people's keys)
gpg --list-keys

# List private keys (generally only your own)
gpg --list-secret-keys

gpg --edit-key <USER_ID>

# Find the ID of your key first
# The ID is the hexadecimal number
# Second column, after the slash, e.g. "ABC12345"
# If you have a "sub" entry, you can ignore it
gpg --list-secret-keys

# This is your private key keep it secret!
# Replace XXXXXXXX with your hexadecimal key ID
gpg --export-secret-keys --armor XXXXXXXX > ./my-priv-gpg-key.asc
# or
gpg --export-secret-keys XXXXXXXX > ./private.key

# Omitting the --armor flag will give you binary output instead of ASCII
# which would result in a slightly smaller file but the ASCII
# formatted (armored) can be printed physically, is human readable,
# and transfered digitally easier.
# Both formats can be imported back in to GPG later

# This works the same for binary or ASCII (armored) versions of keys
# This is also the same for private and public keys
gpg --import ./my-priv-gpg-key.asc
# or
gpg --import ./private.key

# You can also directly import a key from a server
# For example, import the DevDungeon/NanoDano public GPG key from MIT
gpg --keyserver pgp.mit.edu  --recv C104CDF0EDA54C82

# There are many public key servers out there, not just MIT
# Replace XXXXXXXX with your key id from --list-keys
gpg --keyserver hkp://pgp.mit.edu --send-keys XXXXXXXX

# Private keys
# Use the ID listed with --list-secret-keys
gpg --delete-secret-keys XXXXXXXX

# Public keys
# Use the ID listed with --list-keys
gpg --delete-keys XXXXXXXX

gpg --symmetric message.txt
# Prompts you for a passphrase
# Creates message.txt.gpg (binary)

gpg --armor --symmetric message.txt
# Same, but ASCII format output instead of binary
# Creates message.txt.asc (ASCII)

# Specify the encryption algorithm
gpg --symmetric --cipher-algo AES256

# Get the list of cipher algorithms
gpg --version
# E.g. 3DES, BLOWFISH, AES256, TWOFISH

# Specify output file
gpg --output message.txt.gpg --symmeteric message.txt

# Encrypt and sign (all in the single output file)
gpg --sign --symmetric message.txt

# This will prompt and ask the recipient's email address
# and you will have to enter the ID or email
gpg --encrypt message.txt

# or specify the recipient as the -r argument
gpg  --recipient nanodano@devdungeon.com --encrypt message.txt
# Encrypted output will be in message.txt.gpg

# Encrypt and store in ASCII format (message.txt.asc)
# Both binary and ASCII versions decrypt the same
gpg  --armor --recipient nanodano@devdungeon.com --encrypt message.txt

# Encrypt and sign at the same time
gpg --encrypt --sign --recipient nanodano@devdungeon.com message.txt

# Specify output file
gpg --output message.txt.gpg 

# Decrypt and print message to screen
# Will automatically verify signature if there was one
# Will automatically detect if symmetric or asymmetric
# Will automatically use the appropriate private key if available
# Will automatically prompt for passphrase if symmetric
gpg -d message.txt.gpg

# Decrypt and put output in decrypted.txt
gpg --decrypt message.txt.gpg > decrypted.txt

gpg --clearsign message.txt
# Outputs message.txt.asc in plain text, suitable
# for pasting in an email or posting online

gpg --sign message.txt
# Outputs message.txt.gpg a binary file

# Both of these can be verified with --decrypt
# but they are not _actually_ encrypted.
gpg --decrypt message.txt.gpg
gpg --decrypt message.txt.asc
# This will print out the message along with the signature info

# Symmetric encrypt with signature
gpg --sign --symmetric message.txt

# Asymmetric encrypt with signature
gpg --sign --encrypt --recipient nanodano@devdungeon.com message.txt

# When you decrypt the message it will verify the signature
gpg --decrypt message.txt.asc

# Verify a signed message that included a signature
gpg --verify message.txt.asc
# Verify and extract original document
gpg --output message.txt message.txt.asc

# Create a separate signature file
gpg --detach-sign message.txt
# Will create message.txt.sig

# This verify will automatically check the signature
# against a file named "message.txt"
gpg --verify message.txt.sig

# Specify the file to check it against
gpg --verify some_signature.sig ./message.txt