In the Windows GUI, all the controls that were previously named or
labelled Ed25519 are now labelled EdDSA, and when you select that
top-level key type, there's a dropdown for the specific curve (just
like for ECDSA), whose only current value is Ed25519.
In command-line PuTTYgen, you can say '-t eddsa' and give a number of
bits, just like '-t ecdsa'. You can also still say '-t ed25519', for
backwards compatibility.
Also in command-line PuTTYgen, I've reworked the error messages if you
give a number of bits that doesn't correspond to a known elliptic
curve. Now the messages are generated by consulting the list of
curves, so that that list has to be updated by hand in one fewer
place.
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