- OpenPGP
- The open standard (RFC 4880) for PGP encryption and signing, implemented by tools like GnuPG, OpenPGP.js, and many email clients. PGP is the brand; OpenPGP is the spec.
- Public-key cryptography
- An asymmetric scheme where each user has a key pair: the public key encrypts and verifies, the private key decrypts and signs. Knowing the public key reveals nothing about the private key.
- ASCII armor
- Base64 encoding of binary PGP data with human-readable -----BEGIN/END----- header lines, enabling PGP data to travel safely through plain-text channels like email and chat.
- Key ring
- A local collection of OpenPGP keys you trust or own. GnuPG stores public keys in pubring.gpg/pubring.kbx and private keys in secring.gpg/private-keys-v1.d. This tool does not maintain a persistent key ring.
- Web of trust
- A decentralized PGP trust model where users sign one another's keys to attest identity, building a graph of vouched relationships. An alternative to centralized certificate authorities.
- RSA vs ECC
- RSA is an integer-factorization-based algorithm (key sizes 2048–8192 bits); ECC (elliptic curve, curve25519/ed25519) provides equivalent security with 32-byte keys. ECC is faster, smaller, and recommended for new keys.
- Passphrase
- A secret used to encrypt a private key on disk. Without the passphrase, a stolen private key file cannot be used. Required when decrypting or signing with a passphrase-protected key.
- Fingerprint
- A short hash of a public key (typically 40 hex characters for SHA-1, 64 for SHA-256) used for out-of-band identity verification — easier to compare by phone or in person than a full key block.