Relying on a passphrase only is not good enough. Enter it once on a compromised system and it's game over. Since your ID is tied to your passphrase you even have an issue and you will need to revoke your public key.
Many years ago, people realised you need to rely on something more than knowledge (of a password/passphrase) alone. Pick any two out of {something you know,something you own,something you are}, the latter being implemented by biometry.
That's why you need your ATM card, and why it has a PIN code.
This is a step back into a world were security wasn't good enough. Security is more than crypto alone, it's mainly about keeping things secret. There are too many ways a passphrase could be compromised or discovered.
This approach focuses too much on the crypto aspects, and not enough on all the other things involved in building something that is secure.
> Enter it once on a compromised system and it's game over
The same is true of any heavily used system today. All systems: banks, credit cards, facebook, etc. use "something you know". "Something you own" has just recently picked up steam in the form of two factor authentication, but then again, how many people you know actually use that?
The only thing that I know of/heard of that might hold up against the type of attack that you describe is the behavioral keys: i.e. a key which is something about you that you dont necessarily know yourself, e.g. your style of chess, or your phrasing of sentences.
Many years ago, people realised you need to rely on something more than knowledge (of a password/passphrase) alone. Pick any two out of {something you know,something you own,something you are}, the latter being implemented by biometry.
That's why you need your ATM card, and why it has a PIN code.
This is a step back into a world were security wasn't good enough. Security is more than crypto alone, it's mainly about keeping things secret. There are too many ways a passphrase could be compromised or discovered.
This approach focuses too much on the crypto aspects, and not enough on all the other things involved in building something that is secure.