Add comment about using TPM based RNG for start auth nonce

[dgarske]

ZD 21476

[Copilot]

Pull request overview

Note

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Adds security-focused documentation to discourage using TPM RNG output over SPI/I2C for session nonce generation unless the bus is physically protected, and makes the local wolfCrypt RNG the documented default for nonce generation.

Changes:

• Expanded wolfTPM2_GetRng() documentation to warn about HW RNG data exposure on SPI/I2C.
• Added rationale comment for defaulting to local wolfCrypt RNG (when available) instead of TPM2_GetRandom.
• Updated TPM2_GenNonce() documentation to warn about nonce tampering risk when using WOLFTPM2_USE_HW_RNG.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
wolftpm/tpm2_wrap.h	Adds Doxygen warning around using TPM RNG over an unprotected bus.
wolftpm/tpm2.h	Documents default nonce RNG choice and updates nonce-generation API docs with a bus-tampering warning.

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