http://riseup2a3go3phwiacrkq35qj2mjuankua4oxbu3b6nwil77soa5k6qd.onion/en/security/network-security/riseup-ca
This centralized authority model has troubling social and political ramifications, especially when we rely on it for security. Some day, we hope that alternative, non-heriarchical models will replace this flawed system. Until then, Riseup has purchased certificates from a commercial certificate authority that is recognized by your web browser, mail client, or chat client.