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What causes the "unsupported protocol" error when accessing a site via browser after installing a Guomi SSL certificate?

This error usually occurs because the browser does not support Guomi algorithms, or the server is not correctly configured with dual certificates.

1. Browser compatibility​

Guomi SSL is based on the GMTLS protocol (Guomi Transport Layer Security protocol). The following major international browsers do not support Guomi algorithms by default:

  • Chrome
  • Firefox
  • Safari
  • Edge

Please use the following browsers that support the Guomi protocol for access:

  • Qi An Xin Trusted Browser
  • Red Lotus Browser
  • Other domestic browsers that support Guomi GMTLS

2. Server configuration recommendations (dual certificate mode)​

To support access from both Guomi and non-Guomi environments, we recommend deploying both a Guomi certificate and an international RSA certificate (dual certificate mode) on the server.

  • Deploying only a Guomi certificate → Non-Guomi browsers will directly refuse the connection because they cannot match the cipher suite, resulting in the above error
  • Deploying both Guomi and RSA dual certificates → Guomi browsers will use the Guomi certificate, and standard browsers will use the RSA certificate, ensuring compatibility across all scenarios
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