Rich Authorization in a Resource Constrained Device
Talkat Linux Security Summit North America 2019 · on Tuesday, 2019-08-20· at 11:35· Sapphire D, Hilton San Diego Bayfront·
summary
TPM 2.0 implements rich authorization on very small devices (hundreds of bytes of RAM) by keeping one fixed-size policy digest per entity (typically 32-byte SHA-256 digest) and a tiny opaque session state. It supports immediate vs deferred assertions, AND/OR composition, command-code, signature-with-nonce/expiry, NV-indexed secrets, PCR and counter-based revocation, and a policyAuthorize indirection plus policyAuthorizeNV to allow safe policy changes. Designers report typical policies use ~3–4 ANDs and up to 3 ORs; implementations are backward-compatible and already in use.
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chapters (13)
- 0:00Start
- 3:53Policy Mechanism - Immediate
- 4:37Policy Mechanism - OR
- 5:46Feature Summary
- 8:01Policy Command Code
- 9:53Policy Authorization Value Policy Password
- 10:28Policy Signed
- 13:18Policy Secret
- 14:12Policy Command Parameter Hash
- 17:06Policy NV Written
- 18:19Policy Counter Timer
- 19:32Issues
- 26:10Policy AuthorizeNV
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