Overview

This Wikipedia article documents ssh-keygen, a standard command-line utility in the Secure Shell (SSH) suite for Unix, Unix-like, and Windows systems, written in C and developed by the OpenBSD Project under BSD, ISC, and public-domain licenses. The tool generates, manages, and converts the authentication keys used to establish secure, password-free remote connections over insecure networks. It supports multiple public-key algorithms and stores generated keypairs in a user’s ~/.ssh/ directory. Ed25519, the modern recommended key type, is highlighted for performing faster than RSA with significantly smaller keys.

Key points

• ssh-keygen creates asymmetric keypairs (a private key plus a matching .pub public key) for SSH host and user authentication.
• Supported key types selected via the -t flag: RSA (universally supported), DSA (deprecated since 2013), ECDSA, and Ed25519 (recommended).
• Ed25519 is an EdDSA signature scheme over the twisted Edwards curve Curve25519; it uses fixed 256-bit keys and is faster than RSA while producing much smaller keys.
• For SSH protocol version 2, keys default to files such as id_ed25519 / id_ed25519.pub and id_rsa / id_rsa.pub inside $HOME/.ssh/.
• Common options include -t (key type), -b (bit length; default 3072 for RSA), -C (comment), -p (change passphrase), and -o (new OpenSSH private-key format).

Relevance to Truestamp

Ed25519, the key type this utility recommends, is the same elliptic-curve signature scheme Truestamp uses to sign its cryptographic data structures; see Ed25519 signatures. The article is useful background on how Ed25519 keypairs are generated and stored in a widely deployed real-world tool.

Citations

1. ssh-keygen: Wikipedia. Wikipedia, community-maintained reference article.