mirror of
https://github.com/tpm2dev/tpm.dev.tutorials.git
synced 2024-11-14 02:32:10 +00:00
20 lines
873 B
Markdown
20 lines
873 B
Markdown
# Endorsement Keys are (Generally) Decrypt-Only
|
|
|
|
All TPMs (2.0) must have decrypt-only Endorsement Keys (EKs).
|
|
|
|
Some TPMs may have signing-only EKs. E.g., Google cloud vTPMs have
|
|
signing-only EKs as well as decrypt-only EKs.
|
|
|
|
Somehow one must make do with decrypt-only EKs to authenticate a TPM.
|
|
The obvious answer is to make the TPM prove possession of an EK by
|
|
sending a challenge encrypted to the EK's public key (EKpub).
|
|
|
|
This is what [`TPM2_MakeCredential()`](TPM2_MakeCredential.md) (encrypt)
|
|
and [`TPM2_ActivateCredential()`](TPM2_ActivateCredential.md) (decrypt)
|
|
are all about, except that they add some structure to the plaintext and
|
|
semantics to the decryption function.
|
|
|
|
See [README](README.md) for details of how
|
|
[`TPM2_MakeCredential()`](TPM2_MakeCredential.md) and
|
|
[`TPM2_ActivateCredential()`](TPM2_ActivateCredential.md) are used in
|
|
attestation protocols.
|