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                         PASSKEY FAILURE MATRIX
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CASE NAME                    | RESULT           | ENGINEERING REASON
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valid_login                  | ACCEPT           | Challenge is fresh, origin and RP ID match, signature is ...
replay_old_assertion         | REJECT           | Assertion rejected: Challenge mismatch: received 'GxRal5X...
wrong_origin                 | REJECT           | Assertion rejected: Origin mismatch: received 'https://ev...
wrong_rp_id                  | REJECT           | Assertion rejected: RP ID hash in authenticatorData does ...
tampered_challenge           | REJECT           | Assertion rejected: Challenge mismatch: received 'tampere...
wrong_credential_id          | REJECT           | Assertion rejected: Credential ID does not exist in Relyi...
wrong_public_key             | REJECT           | Assertion rejected: ECDSA P-256 signature verification fa...
public_key_database_leak     | NO DIRECT LOGIN  | Since the server only stores the public key, database the...
private_key_compromise       | CRITICAL         | Stolen private keys allow direct account takeover. The se...

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Scenario:     valid_login
Action:       Normal authentication flow
Checks:       Credential ID exists, Challenge, Origin, RP ID, Signature, Increasing counter
Result:       ACCEPT
Description:  Challenge is fresh, origin and RP ID match, signature is correct, counter increased.
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Scenario:     replay_old_assertion
Action:       Attacker replays previous AssertionResponse containing challenge c1
Checks:       Challenge match in clientDataJSON
Result:       REJECT
Description:  Assertion rejected: Challenge mismatch: received 'GxRal5XM2-HASjHIQSKPygZD-7aBFXo7iDZgWI1qVqo', expected 'ThdGx3GiHREogC77siKFpWhpwQgWWQ-yycHf6jFV1mA'.
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Scenario:     wrong_origin
Action:       Browser reports phished origin in clientDataJSON
Checks:       clientDataJSON origin == server expected origin
Result:       REJECT
Description:  Assertion rejected: Origin mismatch: received 'https://evil-phish.com', expected 'https://rp.example.com'.
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Scenario:     wrong_rp_id
Action:       Authenticator includes different RP ID hash in authenticatorData
Checks:       SHA256(server RP ID) == RP ID hash in authenticatorData
Result:       REJECT
Description:  Assertion rejected: RP ID hash in authenticatorData does not match expected relying party.
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Scenario:     tampered_challenge
Action:       Client submits altered challenge in clientDataJSON
Checks:       clientDataJSON challenge == server outstanding challenge
Result:       REJECT
Description:  Assertion rejected: Challenge mismatch: received 'tampered_challenge_value', expected 'XnrczG-oodtdEAuOIKcWJkVZWGOhrZw-FaUMrOAAp8Y'.
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Scenario:     wrong_credential_id
Action:       Client uses credential ID not registered with the server
Checks:       Credential ID exists in server database
Result:       REJECT
Description:  Assertion rejected: Credential ID does not exist in Relying Party database.
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Scenario:     wrong_public_key
Action:       Server database contains wrong public key for validation
Checks:       Signature verification checks out
Result:       REJECT
Description:  Assertion rejected: ECDSA P-256 signature verification failed.
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Scenario:     public_key_database_leak
Action:       Attacker steals public key DB; tries to log in by creating a forged signature
Checks:       Signature verification against stored public key
Result:       NO DIRECT LOGIN
Description:  Since the server only stores the public key, database theft does not allow account takeover. The attacker must possess the private key to sign the challenge.
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Scenario:     private_key_compromise
Action:       Attacker steals device private key; signs a fresh challenge successfully
Checks:       Signature verification, challenge validity, origin, RP ID
Result:       CRITICAL
Description:  Stolen private keys allow direct account takeover. The server verifies the signature and accepts the login, rendering all security checks ineffective.
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