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FIDO2 Message Details
This message is sent as a request by the AUX MCU to authenticate a FIDO2 credential. The MAIN MCU responds with FIDO2 Authenticate Credential Response. The message is used to check whether the authenticator has the specified credential or not.
From AUX MCU:
| byte 8 - 259 | byte 260 - 275 |
|---|---|
| RPID | Credential ID |
RPID
RPID for the request.
Credental ID
The CredentialID that the authenticator is requested to check whether it already exists or not.
This message is sent as a response to request by the AUX MCU to authenticate a FIDO2 credential.
From MAIN MCU:
| byte 8 - 23 | byte 24 - 87 | byte 88 | byte 89 |
|---|---|---|---|
| Credential ID | User handle | User handle length | Result |
Credental ID
The CredentialID that was checked.
User handle
User handle associated with the credential
User handle length
The length of the user handle.
Result
| Value | Description |
|---|---|
| 0x00 | Authenticator does not have the credential |
| 0x01 | Authenticator does have the credential |
This message is sent as a request by the AUX MCU to create a credential for a FIDO2 credential. The MAIN MCU responds with FIDO2 Make Credential Response. See FIDO2 specification for definition of the values that are not explicitly defined here.
From AUX MCU:
| byte 8 - 259 | byte 260 - 323 | byte 324 | byte 325 - 389 | byte 390 - 454 | byte 455 - 486 | byte 487 |
|---|---|---|---|---|---|---|
| RPID | User Handle | User handle length | User name | Display name | Client Data Hash | Key Type |
RPID
RPID for the request.
User Handle
User handle associated with the credential
User handle length
The length of the user handle.
Display name
Display name as per FIDO2 spec.
Client data hash
Key Type
| Value | Description |
|---|---|
| 0x00 | ES256 (ECDSA over NIST P-256 with SHA-256) |
| 0x01 | EdDSA (Curve25519 with SHA-512) |
This message is sent as a response to request by the AUX MCU to make credential for a FIDO2 credential. See FIDO2 specification for definition of the values that are not explicitly defined here.
From MAIN MCU:
| byte 8 - 23 | byte 24 - 55 | byte 56 - 59 | byte 60 - 63 | byte 64 - 95 |
|---|---|---|---|---|
| Credential ID | RPID Hash | Count (in BE format) | Flags | Public key x component |
| byte 96 - 127 | byte 128 - 191 | byte 192 - 207 | byte 208 - 211 | byte 212 | byte 213 |
|---|---|---|---|---|---|
| Public key y component | Attest signature | AAGUID | Credential ID length | Key Type | Error code |
Credental ID
The CredentialID for the entry to check
RPID Hash
SHA256 hash of the RPID
Count (in BE format)
Count as per FIDO2 spec.
Flags
Flags as per FIDO2 spec.
Public key x/y components
Public key x/y components, encoding
Attest signature
AAGUID
Credential ID length
Key Type
| Value | Description |
|---|---|
| 0x00 | ES256 (ECDSA over NIST P-256 with SHA-256) |
| 0x01 | EdDSA (Curve25519 with SHA-512) |
Error code:
| Value | Description |
|---|---|
| 0x00 | Success. Credential created and stored |
| 0x01 | Operation Denied. User denied the operation |
| 0x02 | User not present. The user prompt to create the credential timed out |
| 0x03 | Storage exhausted. The database storage does not have room |
This message is sent as a request by the AUX MCU to create assert a FIDO2 credential. The MAIN MCU responds with FIDO2 Get Assertion Response. See FIDO2 specification for definition of the values that are not explicitly defined here.
From AUX MCU:
| byte 8 - 259 | byte 260 - 291 | byte 292 - 455 | byte 456 |
|---|---|---|---|
| RPID | Client Data Hash | Allow List | Flags |
RPID
RPID for the request.
Client data hash
Allow List
Allow list is the list of allowed credentials to be asserted. The list can contain 0 or more credentials. If 1 or more credentials is specified we can only assert one of these (based on user selection). See parameter name "allowList" at https://fidoalliance.org/specs/fido-v2.0-ps-20190130/fido-client-to-authenticator-protocol-v2.0-ps-20190130.html#authenticatorGetAssertion
| byte 292 - 295 | byte 296 - 311 | byte 312 - 327 | byte 328 - 439 | byte 440 - 455 |
|---|---|---|---|---|
| Length | Credential ID 1 | Credential ID 2 | ... | Credential ID 10 |
Length
Number of "Credential IDs" following. Valid value is 0 - 10.
Credential ID X
The CredentialID to present to the user to ask for assertion.
Flags
Flag for the operation
| Value | Description |
|---|---|
| 0x00 | Normal operation |
| 0x01 | Silent Get Assertion. Do not prompt user |
This message is sent as a response to request by the AUX MCU to a Get Assertion Request. See FIDO2 specification for definition of the values that are not explicitly defined here.
From MAIN MCU:
| byte 8 - 23 | byte 24 - 87 | byte 88 | byte 89 - 120 | byte 121 - 124 | byte 125 - 128 |
|---|---|---|---|---|---|
| Credential ID | User Handle | User Handle Length | RPID Hash | Count (in BE format) | Flags |
| byte 129 - 192 | byte 193 - 208 | byte 209 | byte 210 |
|---|---|---|---|
| Attest signature | AAGUID | Key Type | Error code |
Credental ID
The CredentialID for the entry to check
User handle
User handle associated with the credential
User handle length
The length of the user handle.
RPID Hash
SHA256 hash of the RPID
Count (in BE format)
Count as per FIDO2 spec.
Flags
Flags as per FIDO2 spec.
Attest signature
AAGUID
Key Type
| Value | Description |
|---|---|
| 0x00 | ES256 (ECDSA over NIST P-256 with SHA-256) |
| 0x01 | EdDSA (Curve25519 with SHA-512) |
Error code:
| Value | Description |
|---|---|
| 0x00 | Success. Credential asserted |
| 0x01 | Operation Denied. User denied the operation |
| 0x02 | User not present. The user prompt to assert the credential timed out |
| 0x03 | N/A |
| 0x04 | No credentials available for requested RPID |