public byte[] getSecretKey() throws GuacamoleException {
        return environment.getRequiredProperty(JSON_SECRET_KEY);
    }
Returns the symmetric key which will be used to encrypt and sign all
JSON data and should be used to decrypt and verify any received JSON
data. This is dictated by the "json-secret-key" property specified
within guacamole.properties.

@return
    The key which should be used to decrypt received JSON data.

@throws GuacamoleException
    If guacamole.properties cannot be parsed, or if the
    "json-secret-key" property is missing.
extensions/guacamole-auth-json/src/main/java/org/apache/guacamole/auth/json/ConfigurationService.java