ED25519, ECDSA, RSA encryption to choose for AlmaLinux 9

For generating new SSH keys, each algorithm has its pros and cons, so here’s a quick overview of the best choices for most purposes:

1. ED25519

   • Pros: ED25519 is fast and highly secure with a shorter key length, making it efficient in performance and storage. • Cons: Not compatible with very old systems that may not support it. • Recommendation: Recommended for most users if both the server and client support it. • Generate:

ssh-keygen -t ed25519 -C “[email protected]”

2. ECDSA

   • Pros: ECDSA (Elliptic Curve DSA) offers shorter key sizes and good performance. • Cons: Not as universally supported as RSA, and ED25519 is often preferred over ECDSA due to similar strengths. • Recommendation: Use only if compatibility with older systems requires it and ED25519 isn’t an option. • Generate:

ssh-keygen -t ecdsa -b 521 -C “[email protected]”

3. RSA

   • Pros: RSA is the most widely compatible key and still very secure with a key size of at least 3072 or 4096 bits. • Cons: Slightly larger key sizes lead to slower performance than ED25519. RSA-2048 is no longer recommended for long-term use; at least 3072 bits is advised. • Recommendation: Good choice for compatibility if you need to work with older systems. • Generate:

ssh-keygen -t rsa -b 4096 -C “[email protected]”

Summary Recommendation

For a modern and secure setup on AlmaLinux, ED25519 is the recommended option if compatibility isn’t an issue. If you’re looking for broader compatibility, go with RSA (4096-bit).