If the private key is stored on the TPM chip, if the crypto takes place on the TPM chip, and if the remote service knows your public key (or, more likely, a mas

If the private key is stored on the TPM chip, if the crypto takes place on the TPM chip, and if the remote service knows your public key (or, more likely, a master key which signed your key), then you won't be able to break the scheme by intercepting the request. Of course, even though the general scheme might be sound, there might still be a lot of possible attacks. I'm not saying it's unbreakable.