What does HRESULT 0x80EE0064 (RTC_E_SIP_TLS_INCOMPATIBLE_ENCRYPTION) mean?

RTC_E_SIP_TLS_INCOMPATIBLE_ENCRYPTION

Operational meaning: RTC_E_SIP_TLS_INCOMPATIBLE_ENCRYPTION

This result is useful only when preserved with its producing phase; in selecting an allowed authentication method, validating the challenge realm, and establishing a protected SIP transport, it denotes client and server TLS capabilities or configured cipher/security requirements cannot establish a compatible protected channel.

The machine-readable identity of this result is 0x80EE0064 in the RTC interface facility 0xEE; the result identity matters because RTC uses separate facilities for API conditions, SIP final responses, and PINT service statuses.

The first useful check is to capture protocol/cipher negotiation outcome, policy, certificate path, and peer endpoint. The result must be separated from nearby conditions because this differs from an invalid certificate because cryptographic negotiation fails before or apart from identity validation.

Signals worth preserving

Do not wait for a generic failure notification to log this result; preserve the API call or event producing it together with the RTC object and transaction state visible at that moment.

• Code-specific proof: capture protocol/cipher negotiation outcome, policy, certificate path, and peer endpoint.
• Correlation key: certificate subject and validation failure.
• Protocol or object snapshot: client/server UTC time and TLS phase.
• Last completed transition: 401 or 407 challenge source.
• Expected output: authentication scheme and realm.

Protocol and object state

RTC profile rules tie some authentication methods to TCP or TLS; Basic authentication requires TLS in the legacy API contract. A certificate failure, a challenge mismatch, and invalid credentials occur at different layers and need different remediation.

Verification workflow

1. Record it and 0x80EE0064 at the first RTC method or event that returns it.
2. Identify the client, profile, session, participant, presence object, terminal, or port manager that owns this occurrence.
3. Place the result in its exact phase: parsing, discovery, transport, authentication, profile validation, dialog control, media, roaming, registration, redirection, or final response handling.
4. Prove the condition by ensuring the trace can capture protocol/cipher negotiation outcome, policy, certificate path, and peer endpoint.
5. Apply one controlled change: align supported TLS/security configuration without disabling required protection; then verify the result return value and resulting RTC state.

Diagnosis is strongest when object state and protocol trace share timestamps and transaction identifiers; avoid treating packet capture and HRESULT logging as substitutes for one another.

Do not confuse it with

Use “client and server TLS capabilities or configured cipher/security requirements cannot establish a compatible protected channel” as the discriminator when comparing the related RTC results below.

Recovery and control flow

The corrective direction is to align supported TLS/security configuration without disabling required protection; for this HRESULT, cancellation, cleanup, and retry should remain with the component that owns the failed transition.

Do not turn this result into an immediate unconditional retry; first determine whether the peer could have accepted the prior request and whether RTC still owns a live transaction.

Example: A hardened server and legacy RTC client share no allowed TLS cipher configuration.

Actions that do not address this condition

• Never record Authorization header contents or plaintext passwords.
• Do not disable certificate checking or lower transport security to make authentication appear successful.

Verification after a fix

Verify the fix with a minimal deterministic case that reaches “client and server TLS capabilities or configured cipher/security requirements cannot establish a compatible protected channel”; the failing case must assert the HRESULT and post-failure state; the passing case should alter one input and confirm both protocol outcome and cleanup.

Technical references

• Microsoft profile creation rules.
• Microsoft RTC return constants.
• SIP authentication and TLS.

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