I thought the point of the TPM was that the keys would be kept internally to the TPM at all times and that any data lanes would only be used for transferring payload. Why are they sending keys between the TPM and the CPU?
Because the CPU has to decrypt the bulk of the data coming from the disc. And it needs a key to do that. Unless we route all traffic through the TPM to decrypt the disc. The CPU needs a key to do that
Surely some smart key exchange algorithm could be used for that, e.g. the CPU provides a public key to the TPM and the TPM encrypts the symmetric disk key with that public key. Similar to how TLS works.
The private key would have to stored in clear text somewhere. Potentially if you had non volatile space on cpu that to store the private key, that might work. But if you’re going to do that, might as well just use an ftpm.
I thought the point of the TPM was that the keys would be kept internally to the TPM at all times and that any data lanes would only be used for transferring payload. Why are they sending keys between the TPM and the CPU?
Because the CPU has to decrypt the bulk of the data coming from the disc. And it needs a key to do that. Unless we route all traffic through the TPM to decrypt the disc. The CPU needs a key to do that
Surely some smart key exchange algorithm could be used for that, e.g. the CPU provides a public key to the TPM and the TPM encrypts the symmetric disk key with that public key. Similar to how TLS works.
The private key would have to stored in clear text somewhere. Potentially if you had non volatile space on cpu that to store the private key, that might work. But if you’re going to do that, might as well just use an ftpm.