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SSH Key Converter

Fingerprint Check to Confirm the Same Key After OpenSSH, PuTTY and PKCS#1 Conversion

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How the SSH Key Converter works

This SSH key converter turns a public key from one format into another: OpenSSH one-line keys, RFC 4716 SSH2 blocks, PEM SPKI and PEM PKCS#1. It detects the input format for you and shows the SHA256 fingerprint of the result so you can confirm nothing changed but the wrapping.

What the SSH key converter changes

Every format holds the same public numbers. OpenSSH puts the key type, base64 blob and comment on one line for authorized_keys. RFC 4716, the SSH2 format from PuTTYgen and commercial SSH servers, wraps the same blob between ---- BEGIN SSH2 PUBLIC KEY ---- lines with an optional quoted comment. PEM SPKI is the BEGIN PUBLIC KEY form that OpenSSL, Java and most libraries read, and PKCS#1 is the older RSA-only BEGIN RSA PUBLIC KEY form.

The converter handles RSA, Ed25519 and ECDSA on P-256, P-384 and P-521. It is the browser equivalent of ssh-keygen -e -m PKCS8 and ssh-keygen -i -m PKCS8. Leave the comment blank to keep the original one.

FAQ

How do I convert a PuTTY public key for authorized_keys?

Paste the SSH2 block PuTTYgen saves, starting with ---- BEGIN SSH2 PUBLIC KEY ----, and choose OpenSSH. The result is one line you can append to ~/.ssh/authorized_keys. The PuTTY private key file (.ppk) is a different thing and needs PuTTYgen itself.

Why can't Ed25519 be converted to PKCS#1?

PKCS#1 only defines RSA keys, so there is no PKCS#1 form for Ed25519 or ECDSA. Choose PEM SPKI instead, which is the general public key container that every modern library reads for all three key types.

Does converting change the fingerprint?

No. The fingerprint is a hash of the key blob, which every format carries unchanged, so the fingerprint shown under the result matches the one for your original key. If they ever differ, the input was a different key.

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