From: tpm2 [mailto:firstname.lastname@example.org] On Behalf Of Caiqishen
Sent: Tuesday, June 18, 2019 12:11 AM
Subject: [tpm2] How to implement key distribution using tpm2_import and
In the book, "A Practical Guide to TPM 2.0", there's a process describing
distribution which is as the following:
1. The central IT system creates an HMAC key using TPM2_GetRandom.
2. The central IT system encrypts the HMAC key with the public portion of
the target client’s storage key.
3. The central IT system signs the encrypted HMAC key with its private
signing key. This is done so the local platform knows that what is being sent is
authorized by IT.
4. The encrypted HMAC key is sent to the client along with a signature that
proves it came from the central IT system.
5. The client verifies the signature on the encrypted key by loading the
central server’s public key. (This can be done with the TPM using TPM2_Load and
then using TPM2_VerifySignature, if you like.)
6. The client imports the verified, encrypted HMAC key into its system using
TPM2_Import, getting out a loadable, encrypted blob containing the HMAC key.
7. The client loads the HMAC key when the user wishes to use it, using
TPM2_Load, and uses it as normal. At this point, the local platform has received
an HMAC key from the IT central
8. system that has never been decrypted in the local system’s memory.
I wonder how to encrypts the HMAC key and how to import it using
TPM2_Import? How to import a symmetric key encrypted by a rsa public key?
Appreciate for any replies, thanks!
You would reverse the steps:
1. The receiving application would check that IT signature matches and that the cert chain
is valid. Use normal OSSL.
2. decrypt the blob (key) with RSA Decrypt using the TPM private key corresponding with
the public portion used for encrypt
3. Now that you have the plaintext blob (actual symmetric key), call tpm2_import.