I've got recently a problem when I've updated and tried to install Oracle on a new desktop PC. Windows 8.1 is the OS running currently on it. Trying to connect to Enterprise Manager using the usual https://localhost:1158/em/ url connection string has failed and the following error was displayed: "The server certificate included a public key that was too weak. (Error code: ssl_error_weak_server_cert_key)". According to a post on stackoverflow, this seems to be due to an update of security on different internet browsers. By the way, the problem occurs on Firefox and Internet Explorer. The goal of this post is to explain how I've resolved it, since the indications done in other links are not sufficient.