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STATUS_TPM_INAPPROPRIATE_ENC
The encryption scheme is not acceptable for this TPM operation
STATUS_TPM_INAPPROPRIATE_ENC is a Windows NTSTATUS value mapped from the TPM facility. For STATUS_TPM_INAPPROPRIATE_ENC, in this package the code belongs to TPM 1.2 style command processing, where Windows software, TBS, the TPM driver, and the hardware device all may be visible in the same failure path.
The relevant area is TPM key and encryption scheme selection. TPM keys and commands carry restrictions on encryption schemes, key usage, and algorithms. This status means the requested encryption method is not permitted for the key or command being used.
The error is not just about algorithm availability. A TPM can support an algorithm globally while still rejecting a scheme for a particular key type, key usage, command, or migration/transport context. Inspect the key parameters and command-specific scheme field together.
Diagnostic focus
- Dump the key usage, algorithm, encryption scheme, and command ordinal.
- Check whether the key was created with properties that permit the attempted operation.
- Do not replace the authorization secret to fix a scheme mismatch; create or select a key with compatible parameters.
References for STATUS_TPM_INAPPROPRIATE_ENC
- TCG: TPM 1.2 Part 1 Design Principles
- TCG: TPM 1.2 Part 2 Structures of the TPM
- TCG: TPM 1.2 Part 3 Commands
- Microsoft: TPM fundamentals
- Microsoft: MS-ERREF NTSTATUS values
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