rules.json

{
  "rules": {
    "users": {
      "$uid": {
        "location": {
          ".write": "$uid === auth.uid",
          ".read": "$uid === auth.uid"
        },
        "twitter": {
          ".write": "$uid === auth.uid",
          ".read": "$uid === auth.uid"
        },
        "public": {
          ".write": false,
          ".read": true
        },
      }
    }
  }
}