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TPM_E_BAD_SCHEME
Read the result in context
TPM_E_BAD_SCHEME (0x8028002A) belongs to TPM 1.2 command processing. The base What Is page already shows the short Windows message; the additional diagnostic value is that this result marks the selected signature or encryption scheme is not valid for the key and TPM 1.2 command combination.
The first producer to identify for this HRESULT is the TPM 1.2 command decoder and state machine. TPM 1.2 is a command/response device with strict binary structures and stateful resources. Windows may present the device response as an HRESULT, but the diagnostic meaning still belongs to the command field, key, session, PCR, NV index or lifecycle check named by the TPM specification.
The result value 0x8028002A should remain attached to the symbolic name. Some this result logs store the value as a negative signed integer; others expose only a generic CNG, WMI, BitLocker or enrollment message. Neither substitution identifies the selected signature or encryption scheme is not valid for the key and TPM 1.2 command combination as precisely as it.
Fields worth decoding
- Producer for this HRESULT: the TPM 1.2 command decoder and state machine.
- Rejected invariant: the selected signature or encryption scheme is not valid for the key and TPM 1.2 command combination.
- Decisive capture: algorithm ID, encScheme, sigScheme, key usage, command ordinal, key size, and the scheme list assumed by the calling library.
- Safe comparison: query capabilities and retry with one scheme explicitly supported for the same key type and operation.
Controlled comparison
Build the result minimal case around the original command contract. Use a disposable object when the request can write NV data, advance a counter, change authorization state or consume a lock transition. The comparison is valid only when the caller, TPM generation and security policy remain the same.
| Question | Evidence for this HRESULT |
|---|---|
| What exact state was rejected? | the selected signature or encryption scheme is not valid for the key and TPM 1.2 command combination |
| Which layer owns the result? | The TPM 1.2 command decoder and state machine. |
| What must be correlated? | algorithm ID, encScheme, sigScheme, key usage, command ordinal, key size, and the scheme list assumed by the calling library |
| What is the controlled comparison? | query capabilities and retry with one scheme explicitly supported for the same key type and operation |
Adjacent failure boundaries
| Constant | Checkpoint represented by its standard message |
|---|---|
TPM_E_BAD_DATASIZE | The size of the data (or blob) parameter is bad or inconsistent with the referenced key — a separate checkpoint when compared with this result. |
TPM_E_BAD_KEY_PROPERTY | The key properties in TPM_KEY_PARMs are not supported by this TPM — a separate checkpoint when compared with this result. |
TPM_E_BAD_MODE | A mode parameter is bad, such as capArea or subCapArea for TPM_GetCapability, phsicalPresence parameter for TPM_PhysicalPresence, or migrationType for TPM_CreateMigrationBlob — a separate checkpoint when compared with it. |
The codes above may appear in the same workflow, but they are not aliases. TPM_E_ENCRYPT_ERROR or TPM_E_DECRYPT_ERROR occurs during the cryptographic operation; this code rejects scheme selection.
Repair without destroying evidence
Negotiate or create a key with a compatible scheme rather than changing padding after a failed command. Do not clear ownership, delete keys or reset PCR-related state merely to see whether the message disappears; those actions can destroy the evidence and protected material while leaving serialization or command-order defects unchanged.
Proof for this HRESULT consists of a successful replay plus validation of the intended key, PCR, NV, context, event-log, provider or service result. A software fallback or a newly provisioned blank TPM answers a different question than it.
Source material
- TCG: TPM 1.2 Main Specification — source for the checkpoint.
- TCG: TPM 1.2 Part 2 — Structures — source for the checkpoint.
- TCG: TPM 1.2 Part 3 — Commands — source for the checkpoint.
- Microsoft: TPM Base Services portal — source for the checkpoint.
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