SSH Keys Explained: Why Ed25519 Should Be Your Default

If you're still generating RSA keys with ssh-keygen -t rsa , you're using a 1977 algorithm when a 2011 algorithm (Ed25519) is faster, more secure, and produces shorter keys. The inertia of defaults keeps RSA in use, but there's no good reason for new keys. The key types RSA : The oldest widely-used public key algorithm. Recommended minimum key size is 3072 bits (2048 is still common but increasingly discouraged). Key generation is slow. Signing is slow. But it's universally supported. ECDSA : Elliptic curve DSA. Shorter keys (256 bits provides equivalent security to RSA 3072). Faster operations. But the NIST curves it uses (P-256, P-384) have been criticized for potential backdoors in the curve parameters. Ed25519 : Based on Curve25519 (Daniel Bernstein). 256-bit key. Fastest signing and verification. Deterministic signatures (no random number needed during signing, eliminating an entire class of implementation bugs). No NIST curve concerns. Supported by OpenSSH since 2014 (version 6.5