We are using ALB for mTLS. does it support ed25519?
Hey, have come across something similar before. The short answer is no, ALB mTLS won’t accept Ed25519 client certs. The load balancer on GCP will strictly enforce RSA (2048-4096 bit) or ECDSA (P-256/P-384) with SHA-256+ hashing, so an Ed25519 cert will just fall over during the TLS handshake.
If you’re using Google’s Certificate Authority Service (CAS), it doesn’t support Ed25519 for CA signing keys either, so you’d hit a wall there too.
If Ed25519 was the appeal (smaller key sizes, fast signing), ECDSA P-256 gets you almost all of those benefits and is what Google will steer you toward anyway in my experience.
Couple of docs if it helps: