If you created SSH keys using OpenSSH’s previous experimental post-quantum signature support, OpenSSH 10.6 says to regenerate or remove them. The release, dated October 6, 2026, enables the hybrid signature algorithm ssh-mldsa44-ed25519 under a new name. This is a targeted change for keys made with that earlier experimental support—not a direction to replace every SSH key you use.
What changed in OpenSSH 10.6?
OpenSSH 10.6/10.6p1 enables ssh-mldsa44-ed25519, a hybrid post-quantum signature algorithm. The new algorithm name does not use the @openssh.com vendor-extension suffix that appeared in the previous experimental implementation. The OpenSSH 10.6 release notes, published October 6, 2026, say: “Keys generated with the previous experimental support must be regenerated and/or removed.”
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That instruction is limited to keys generated with the previous experimental support. It does not say to replace conventional Ed25519 keys or every other SSH key in an account.
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What should you do with an old experimental key?
Identify whether you created a key using OpenSSH’s earlier experimental post-quantum signature implementation. If so, follow the release note’s direction: regenerate the key for continued use, or remove it if you no longer need it. Do not assume a key is affected merely because it is an SSH key or because it uses Ed25519.
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The release note does not provide a universal command to locate affected keys, a key-file naming pattern, or a complete migration procedure. The right way to identify and replace a key depends on how you generated and deployed it. Check the documentation for your installed OpenSSH version and confirm that the relevant server, client, or hosting service supports the algorithm you intend to use before relying on it. The release note does not establish compatibility across every endpoint.
How this differs from post-quantum key agreement
Signatures and key agreement have separate jobs in SSH. A signature key is used to authenticate an identity; key agreement helps the client and server establish shared session secrets. OpenSSH’s 10.6 change concerns a post-quantum signature algorithm, not the project’s post-quantum key-agreement defaults.
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OpenSSH’s post-quantum cryptography overview says post-quantum key agreement has been offered by default since OpenSSH 9.0, initially using sntrup761x25519-sha512. It says mlkem768x25519-sha256 was added in 9.9 and became the default key-agreement scheme in 10.0, released in April 2025. Those milestones describe key agreement and do not replace the 10.6 guidance for keys created with the earlier experimental signature support.
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- POWERFUL SECURITY KEY: The Security Key C NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key C NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key C NFC via USB-C and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
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- POWERFUL SECURITY KEY: The Security Key NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key NFC via USB-A and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
- BUILT TO LAST: Made from tough, waterproof, and crush-resistant materials. Manufactured in Sweden and programmed in the USA with the highest security standards.
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- POWERFUL SECURITY KEY: The YubiKey 5 NFC is the most versatile physical passkey, protecting your digital life from phishing attacks. It ensures only you can access your accounts
- WORKS WITH 1000+ ACCOUNTS: Compatible with popular accounts like Google, Microsoft, and Apple. A single YubiKey 5 NFC secures 100+ of your favorite accounts, including email, password managers, and more
- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5 NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
- PRIMARY & SPARE KEYS: Just like having a spare house key, we recommend buying two YubiKeys - one for daily use and one as a spare. That way you’ll never get locked out of your accounts
The practical distinction
| Key or feature | What OpenSSH says |
|---|---|
| Keys created with the previous experimental post-quantum signature support | Regenerate and/or remove them, according to the OpenSSH 10.6 release notes. |
| Hybrid post-quantum signature algorithm enabled in 10.6 | ssh-mldsa44-ed25519; its name omits the earlier @openssh.com suffix. |
| Post-quantum key agreement | A separate function with its own algorithm timeline and defaults; it is not the signature-key change in 10.6. |
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