Linux

GPG Encryption — Encrypt Files and Sign Data

Use GPG (GNU Privacy Guard) to encrypt files with passwords or public keys, sign data to prove authenticity, and manage your key ring.

March 31, 20255 min read

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What is GPG?

GPG (GNU Privacy Guard) implements the OpenPGP standard for:

Encrypting files — only the intended recipient can read them
Signing data — proves the data came from you and wasn't altered
Verifying signatures — confirms authenticity

Generate GPG Keys

gpg --full-generate-key        # Interactive key generation
gpg --list-keys               # List public keys
gpg --list-secret-keys        # List private keys

Symmetric Encryption (Password-based)

# Encrypt with a password (anyone with password can decrypt)
gpg -c secret.txt             # Creates secret.txt.gpg
gpg --symmetric secret.txt    # Same thing, verbose flag

# Decrypt
gpg -d secret.txt.gpg > secret_decrypted.txt

Asymmetric Encryption (Key-based)

# Export your public key to share
gpg --export -a "Your Name" > public.key

# Import someone else's public key
gpg --import their-public.key

# Encrypt a file for a specific recipient
gpg -e -r "recipient@email.com" secret.txt

# Decrypt (uses your private key automatically)
gpg -d secret.txt.gpg

Signing Files

# Sign a file (creates .gpg)
gpg --sign file.txt

# Clearsign (readable + signature in one file)
gpg --clearsign file.txt

# Detached signature (.sig file, original unchanged)
gpg --detach-sign file.txt

# Verify a signature
gpg --verify file.txt.sig file.txt

Key Management

gpg --list-keys                         # List public keys
gpg --delete-key "Name"                 # Delete public key
gpg --delete-secret-key "Name"          # Delete private key
gpg --export -a "Name" > key.pub        # Export public key
gpg --export-secret-keys -a > priv.key  # Backup private key

Asymmetric encryption is more secure — you share your public key freely, and only your private key can decrypt messages sent to you.

Quick Check

Which gpg command encrypts a file using a password (symmetric)?

Exercise

Create a test file, encrypt it symmetrically with GPG, then decrypt it.