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Convert ssh-keygen generated keys for use in PuTTY

Written at 2018-07-01T04:26:00Z.

By default, the keys (with passphases) generated by ssh-keygen cannot be used by PuTTY. This article describes the steps to convert ed25519 keys to a form that PuTTY understands.

Remove passphase from the key

When loading the key (with passphase) generated by ssh-keygen into PuTTY, an error is shown, saying:


Couldn't load private key (unrecognized cipher name)

PuTTY cannot load the private key generated by ssh-keygen.

Assume the private key is test.ed25519, make a copy and remove the passphase.


cp test.ed25519 test.ed25519.putty

ssh-keygen -p -f test.ed25519.putty

When prompted for new passphase, leave the field empty and press Enter.

Import and convert the key

Now the new key (test.ed25519.putty) can be loaded into PuTTY.

The new key can be loaded into PuTTY.

Enter the key passphase and save the private key. The PPK file can be used in PuTTY (and WinSCP).

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