# rpc error: code = Unavailable desc = connection error: desc = "transport: authentication handshake failed: x509: certificate signed by unknown authority"

- **ID:** `go/grpc-tls-certificate-error`
- **Domain:** go
- **Category:** auth_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

The client cannot verify the server's TLS certificate because the CA is not trusted.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 1.60.0 | active | — | — |

## Workarounds

1. **** (95% success)
   ```
   Add the server's CA certificate to the client's trust pool using credentials.NewClientTLSFromFile.
   ```
2. **** (90% success)
   ```
   Use the system root CA pool by ensuring the server uses a publicly trusted certificate.
   ```

## Dead Ends

- **** —  (90% fail)
- **** —  (80% fail)