Practical use and limits
Use it for: Maintain a small key inventory with owner, device, purpose, server scope, creation date, last review, and revocation action; test the recovery path before a device is lost.
Limits: No single key-management pattern fits every threat model. Separate identities reduce blast radius but add recovery and inventory work.
Model the real risk
A remote-development setup has at least four trust relationships: your device, the private key, the server host key, and the account or tool that uses the connection. Convenience often hides these boundaries. A single private key copied to several devices expands the blast radius, while several unrelated keys can make recovery confusing. Decide which risk you are optimizing before choosing a format or import flow.
Choose one identity or several
One Ed25519 identity across devices is simple and works when both clients are equally trusted and revocation is manageable. Separate keys per device make audit and revocation clearer: remove only the lost device's public key from authorized_keys. For a small personal server, either model can work; for shared or production systems, per-device or per-person keys are usually easier to govern.
Treat format conversion as an export
If a client requires PKCS8 while another uses OpenSSH, treat the conversion as creating a sensitive credential export. Use a current library, an isolated environment, a known output path, and restrictive permissions. Never upload the source private key to a conversion website. Delete temporary copies securely according to your platform's storage model and confirm the derived public key before use.
Build a recovery path before you need it
Keep a tested console, second administrator, or other authorized access route before rotating the only working key. Document the server address, account, key label, expected host-key verification process, and the exact public-key line to remove. A backup is useful only if you know it is readable and can reach the server without depending on the credential being repaired.
Make the connection observable
Use named SSH Host aliases, explicit IdentityFile entries, and a short runbook. Record the date, device, key label, server, and reason for a change. Keep host-key checking enabled, and use verbose logs only during diagnosis. Avoid placing secrets in shell history, issue trackers, chat messages, screenshots, or environment files that are likely to be committed.
Rotate and revoke deliberately
Rotate when a device is lost, a private key may have been copied, a contractor leaves, or the key has been used outside its intended scope. Add the replacement public key first, test it through the recovery path, then remove the old line. If compromise is suspected, prioritize revocation and server log review over preserving convenience.
Bottom line
Good SSH hygiene is a small operational system: clear identities, supported formats, verified hosts, restrictive permissions, tested recovery, and explicit revocation. The goal is not to make remote development fragile; it is to make the safe path the easiest path to repeat.
Frequently asked questions
Is one key across two devices always unsafe?
No, but every copied private key increases the impact of a loss or exposure. Separate keys improve revocation and auditability, while one key can be acceptable for a tightly controlled personal setup with strong device security.
Where should I store a backup private key?
Use a protected password manager or encrypted offline storage appropriate to your threat model. Do not keep an unencrypted copy in a shared drive, project repository, or chat history.
What should I do first if my phone is lost?
Revoke the phone's public key from every server where it is authorized, review recent authentication logs, and rotate any credential that may have been exposed. Then restore access from a tested recovery path.