Drupal 7, Rules export. Use to redirect anonymous user to frontpage when she tries to access content using node/[nid] path. So content will be available only on its path alias.

drupal_rules_access_alias_only.txt

{ "rules_access_w_alias_only" : {
    "LABEL" : "Acces content with alias only",
    "PLUGIN" : "reaction rule",
    "TAGS" : [ "access" ],
    "REQUIRES" : [ "rules" ],
    "ON" : [ "node_view" ],
    "IF" : [
      { "user_has_role" : {
          "account" : [ "site:current-user" ],
          "roles" : { "value" : { "1" : "1" } }
        }
      },
      { "AND" : [] },
      { "text_matches" : { "text" : [ "site:current-page:url" ], "match" : "node" } }
    ],
    "DO" : [ { "redirect" : { "url" : "[site:url]" } } ]
  }
}