Work out ssh key strength instantly with clear inputs, formula shown and shareable results.
Ed25519 gives 128-bit security in a 68-byte public key and signs roughly ten times faster than RSA 2048, which is why it is the current recommendation for SSH. RSA 4096 provides only about 140 bits — barely more than Ed25519 — while costing far more per operation, so it is a poor trade for a bastion handling many authentications.
Key comparison
security level from NIST equivalences; CPU load = authentications per second x signature cost / 1000
No. DSA is disabled by default in modern OpenSSH and RSA below 2048 bits is deprecated. Both should be removed from authorized_keys.
It has been in OpenSSH since 6.5 and is supported by all current platforms. Very old appliances and some hardware tokens may still require ECDSA or RSA.