Difference Between SSH Key Pair and GPG Key Pair

1. SSH Key Pair

  • Purpose: SSH (Secure Shell) key pairs are primarily used for secure authentication and encrypted communication with remote systems (e.g., logging into a server or transferring files securely).
  • Components:
    • Private Key: Stays on your local system; never shared.
    • Public Key: Shared with the remote server.
  • Protocol: Built on the SSH protocol.
  • Common Algorithms: RSA, ECDSA, ED25519.
  • Use Cases:
    • Logging into remote servers without passwords.
    • Automating secure file transfers (e.g., with scp or rsync).
    • Secure tunneling or port forwarding.
  • Command Example:

ssh-keygen -t ed25519

  • Generates an SSH key pair.

  • ssh-copy-id user@host

    • Copies the public key to the target machine, enabling password-less SSH login.

2. GPG Key Pair

  • Purpose: GPG (GNU Privacy Guard) key pairs are used for encryption, signing, and verification of files, emails, and documents. They ensure confidentiality, integrity, and authenticity in communications.
  • Components:
    • Private Key: Used for decrypting messages and signing data.
    • Public Key: Shared with others to encrypt messages for you or verify your signatures.
  • Protocol: Built on the OpenPGP standard.
  • Common Algorithms: RSA, ECC.
  • Use Cases:
    • Encrypting and decrypting files or emails.
    • Verifying the integrity and authenticity of files.
    • Signing code or software distributions.
  • Command Example:

gpg --gen-key

  • Generates a GPG key pair.

  • gpg --encrypt --recipient user@example.com file.txt

    • Encrypts a file for a specific recipient using their public key.

Conceptual Differences

Conceptual Differences

Feature SSH Key Pair GPG Key Pair
Purpose Secure authentication & communication Encryption, signing, verification
Protocol SSH OpenPGP
Key Sharing Public key shared with remote servers for authentication Public key shared with anyone for encryption and signature verification
Primary Focus Securing remote system access Securing messages, files, and data integrity
Common Commands ssh-keygen, ssh-copy-id gpg --gen-key, gpg --encrypt

When to Use Which

  1. Use SSH Keys:

    • You need secure access to remote servers or services.
    • Automating login without exposing credentials.
    • Use commands like ssh, scp, or rsync.

  2. Use GPG Keys:

    • You need to secure or encrypt sensitive data or emails.
    • Want to digitally sign files or code to verify authenticity.
    • Distribute files with guaranteed integrity and origin verification.