SSH Hardening and Management: Key Management, Bastion Hosts, and SSH Certificates

Calendar February 21, 2026
Infrastructure
Intermediate
Ssh-Hardening, Security-Configuration, Access-Management
Ssh, Security, Hardening, Bastion, Certificates, Tunneling, Key-Management
Ssh, Ssh-Keygen, Sshd, Ssh-Agent

SSH Key Management#

SSH keys replace password authentication with cryptographic key pairs. The choice of algorithm matters:

Ed25519 (recommended): Based on elliptic curve cryptography. Produces small keys (256 bits) that are faster and more secure than RSA. Supported by OpenSSH 6.5+ (2014) – virtually all modern systems.

ssh-keygen -t ed25519 -C "user@hostname"

RSA 4096 (legacy compatibility): Use only when connecting to systems that do not support Ed25519. Always use 4096 bits – the default 3072 is adequate but 4096 provides a safety margin.