ssl_server_ciphers

Specifies the cipher suites used by the server; each suite in the list is separated by a colon (:). This parameter must follow the OpenSSL cipher string syntax. 

ssl_server_ciphers = cipherSuites

For example, you can enable two cipher suites with the following setting: 

ssl_server_ciphers = ECDHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384

See Specify Cipher Suites for more information about the cipher suites available in EMS and the syntax for specifying them in this parameter.