OpenSSH Key Structure Guide
Summary
OpenSSH Key Structure Guide provides a detailed overview of OpenSSH key formats, including legacy PEM private keys, the new OpenSSH private key format (v1), and keytype-specific breakdowns for RSA and ED25519. It covers public/private key structures, base64 encoding, and examples of id_rsa and id_ed25519 formats, along with plaintext and encrypted variants and a reference to PROTOCOL.key for canonical specs.