# 40103: Basic authentication used over an insecure connection

Identifier: `invalid_use_of_basic_auth_over_non_tls_transport`



Basic authentication was attempted over a connection that was not secured with TLS. Basic authentication sends the API key directly, so it is only permitted over an encrypted transport.

## What you should do

Either use Basic authentication over a TLS connection, or switch to [token authentication](https://ably.com/docs/auth/token.md) if you need to connect without TLS. SDKs use TLS by default, so this normally means TLS was explicitly disabled in the client options.

## Why it happens

A client authenticated with an API key (Basic authentication) over a connection that wasn't secured with TLS. Because the key would be exposed to anything inspecting the unencrypted traffic, the request is rejected rather than risk the long-lived credential.

## What you'll see

The error is reported with code 40103 and HTTP status 401. The message is `Invalid use of Basic authentication over non-TLS transport`.