Continuous and Secure In-Flight Wireless LAN with Roaming
Hideaki Goto
Cyberscience Center, Tohoku University
Sendai, Miyagi, Japan

1INTRODUCTION

In-Flight Wireless LAN, or simply In-Flight Wi-Fi in a casual wording, has become an attractive service and many airlines are providing in-flight internet connection today. Some companies are providing free Wi-Fi service only for text messaging, while some others are providing a regular service for free in domestic flights. Paidservice is common in international flights since the airlines have tokeep the costly equipments and backhaul network usage. Some airlines provide roaming service for some Internet Service Providers(ISPs) and telecom operators in addition to the airlines’ own charging system.
The In-Flight Wi-Fi today suffers from various problems regarding security and usability. Open network without encryption iscommonly used despite various security threats including eavesdropping and rogue Access Point (AP) attacks. One of the biggest
obstacles is the disruption of the internet connection to the ground.
Introducing a secure connection means like WPA2 Enterprise, preferably combined with roaming, can solve most security problemsand some usability issues [1]. However, user authentication in thecurrent roaming systems depends on the servers on the groundand suffers from network disruption. Since In-Flight Wi-Fi is becoming indispensable not only for internet connection but also forvarious in-flight services, user devices need to stay connected to
the APs during the entire flight.
We developed earlier a disruption-tolerant Public Wi-Fi system
to realize secure user authentication and to maintain local network
use in temporary isolated areas affected by natural disasters [2].
Since we noticed that the airline use case shares many aspects in
our previous application, we have developed a continuous and secure In-Flight Wi-Fi system based on the previous system. This
presentation1 provides an overview of prospective use cases, problems, and the current development status.

2IN-FLIGHT WI-FI USE CASES AND
CHALLENGES
2.1 In-Flight Wi-Fi and Prospective Use Cases
It is important to think about not only the current In-Flight Wi-Fi
but also prospective use cases and emerging technologies. Figure
1 depicts the current internet connection means for passenger aircrafts. Use of any radio equipments used to be prohibited before,
and still is on older aircrafts, during taxiing, take-off, and landing.
Although some regulations have been relaxed and wireless LAN
usage has been allowed in some newer aircrafts, internet connection may not be available until the aircraft reaches a certain altitude, typically 10,000 ft., due to some technical difficulties, operation rules, and/or regulations.
1 This work was submitted to AINTEC 2021 for review and accepted for poster

presentation.

Use of In-Flight Wi-Fi service is no longer limited to internet
connection today. Many systems provide some flight information,
travel information, weather and transportation information at thedestination, and even allow in-flight shopping. Music/video streaming using an onboard media server is becoming popular. Since manypeople are carrying electronic gadgets today, they would probably
want to use their own players, headphones, smart glasses, etc. InFlight Wi-Fi service has a great potential for improving the services in the air, duplicating or replacing the current service / entertainment system with seat screens. Many prospective services
may not always need internet connection. Therefore, it is becoming more important for airlines to provide hassle-free Wi-Fi service
for any passengers at any time from gate to gate.
Some airlines provide roaming services to make it easy for passengers to get onboard the network. However, the current roaming
systems have some security and usability problems, and the Wi-Fi
industry is trying to introduce secure wireless LAN system with
automatic roaming [1].

2.2

Security and Usability Problems

In order to avoid connecting to a rogue AP, server authenticationneeds to be enabled on user devices. Profile-based configuration isbecoming popular to allow users configure their devices easily in asecure way. Since the profile may contain some digital certificatesand cannot be manually typed in, a user has to install it before
connecting to the secure network in an aircraft. With a roaming,
the passengers do not need to sign-up for a special profile only
for the flight. However, the current roaming systems are based on
web-based authentication, and both the security and the usability
are sacrificed.
User (or client) authentication is needed to enable per-user authorization and encryption. In a roaming environment, the authentication process basically runs between the user device and theauthentication server at the user’s Identity Provider (IdP), e.g., anISP. The conventional methods require that the APs and IdPs arealways connected. As shown in Figure 1, the backhaul network
depends on satellite or Air-To-Ground (ATG) communication, andits disruption is inevitable due to safety regulations, weather conditions, radio coverage, etc. When the internet connection is disrupted, the user authentication is also affected and user devices
may be disconnected from the AP, leading to bad user experiences.

2.3

Continuous Connection and Roaming

Continuous connection to the local network in an aircraft is crucial even when the internet connection is lost. We need a secureauthentication method that can be used on an isolated network. Aroaming feature is also desired in order to provide passengers withhassle-free and seamless network use while they are using multiple
airlines. The roaming feature also needs to be disruption-tolerant,and therefore the conventional method is not appropriate.

Hideaki Goto

(Even at a cruising altitude,
network disruption is inevitable.)satellite communication

10,000 ft.
(No internet service below,
but continuous in-flight service
is in demand.)Air-To-Ground (ATG)
communication

Figure 1: In-Flight Wi-Fi service and internet connection.

Issuer’s
private key

Issuerissue

Client certificate
IssuerUser name
Certificate
User attributes
Signature

Signature verification for authentication.
User attributes for authorization.
Issuer’s
public key
RADIUS

DTN-AP A

Site A

Issuer’s
public key

3.2

RADIUS

DTN-AP B

Site Buser

Figure 2: Certificate-based local authentication
disruption-tolerant wireless LAN service [2].

However, there is a limitation here. In our previous work [2],it was supposed that each prefecture was responsible for accountissuing and that there were not so many network operators. The
number of prefectures in Japan is 47 and the scalability was thought
to be acceptable. The presented method would not work if there
were hundreds of IdPs. Thus, it is not practical to accept directly
the accounts from regular ISPs. A solution would be to delegate
the user account handling to some airline alliances or solution
providers of in-flight services since the number is limited to someextent.
Another challenge is the secure operation and handling of theCA certificates. There might be a threat of certificate leakage since
the CA certificates are loaded on many aircrafts. User devices may
not be able to use Certificate Revocation Lists (CRLs) or Online
Certificate Status Protocol (OCSP) responders when the network
is disrupted. A shorter life time of certificates would work, but it
will increase expirations of client certificates leading to a bad userexperience. Some developments will be needed in this regard.

for3

SECURE AND CONTINUOUS IN-FLIGHT
WI-FI USING LOCAL AUTHENTICATIONMETHOD
3.1 Certificate-based Local Authentication
We developed earlier a secure Public Wi-Fi system whose authentication is tolerant of network disruption. The system was intended
to enable local network use in temporary isolated areas affectedby natural disasters [2]. Figure 2 shows the local authentication
method.
The local authentication is realized by using EAP-TLS [3], which
is one of the methods of Extensible Authentication Protocols usedin WPA2 Enterprise. An account issuer creates a CA (CertificateAuthority) certificate with its public key and distribute it to the regional RADIUS (Remote Authentication Dial-In User Service) servers
in advance. The users receive client certificates in advance. By using the CA certificate, user authentication is possible at each region even without a wide area network connection. Our proposalof continuous and secure In-Flight Wi-Fi system is based on thislocal authentication method.
We assume that an airline or an ISP becomes an account issuer
and that each aircraft corresponds to a service site. If a passengerreceives a client certificate in advance, prior to getting onboard
an aircraft, continuous connection to the in-flight service is realized. For roaming, the in-flight system needs to have CA certificates from multiple account issuers.

Profile Issuing and Roaming

In-Flight Wi-Fi needs to provide various means for passengers to
obtain a profile electronically at any time. In our system, the profile
for the local in-flight connection can be downloaded at an airline
website upon reservation, at home, airport, or anywhere on theground where the internet is available, and also on the local online
sign-up (OSU) system onboard the aircraft. Although such in-flight
OSU may fail in the user and/or credit card verification process
due to network disruption, a semi-online method using a voucher
could help passengers get onboard the In-Flight Wi-Fi.
If a customer is subscribing to a Wi-Fi plan with roaming, associating the regular profile with the in-flight profile would be usefulfor enabling payment through the roaming partners like telecom
companies and ISPs. There may be some possible ways and we aredeveloping an automatic profile association method.

4 CONCLUSIONWe have developed a disruption-tolerant user authentication methodwith roaming capability using digital certificates for realizing continuous and secure In-Flight Wi-Fi. Some more technical developments are under way. From the roaming business point of view,
secure and trusted accounting is quite important. Some modification or adaptation of accounting will also be needed.

ACKNOWLEDGMENTS
This work was supported in part by JSPS KAKENHI No.19H04090.

REFERENCES[1] Wireless Broadband Alliance. 2019. In-Flight Connectivity – Wi-Fi Deployment & User Experience (Issue May 2019).
Retrieved Nov. 8, 2021 fromhttps://wballiance.com/in-flight-connectivity/[2] S. Kinoshita, T. Watanabe, Y. Yamasaki, H. Goto, and H. Sone. 2013. Fault-Tolerant
Wireless LAN Roaming System Using Client Certificates. In IEEE 37th International Conference on Computer Software and Applications (COMPSAC2013). 822–823.
[3] D. Simon, B. Aboba, and R. Hurst. 2008. The EAP-TLS Authentication Protocol.
In RFC5216.

2021/12/16

AINTEC 2021 (Virtual)14-17 Dec. 2021

Continuous and Secure In‐Flight Wireless LANwith Roaming
Hideaki Goto
Tohoku University, Japan(Supported in part by JSPS KAKENHI No.19H04090)

1

1

In‐Flight Wi‐Fi and backhaul network
Satellite / ATG network is evolving, but network
disruption is inevitable. (weather, regulations, etc.)
 We want to avoid interruption of in-flight services suchas music/video streaming, shopping, etc.
Even at a cruising altitude,
network disruption is inevitable.
satellite communication

10,000 ft.

No internet service below,
but continuous in-flight service
is in demand.
Air-To-Ground (ATG)
communication2
2

1

2021/12/16

In‐Flight Wi‐Fi in new era
Various services are depending on Wi-Fi connection.
 Continuous connection to the aircraft network is necessaryfor every passenger,even during backhaul network disruptions.
 User (client) authentication and secure connection means(802.1X, Passpoint) are required for security and privacy protection,
 hassle-free, automatic connection with roaming (e.g.
OpenRoaming),
 better services for subscribers / valued customers.


Research Objectives
Sort out prospective use cases and challenges.
 Develop a continuous and secure In-Flight Wi-Fi systemcapable of roaming with many telcos and ISPs.
(disruption-tolerant authentication method)

33

Certificate‐based local authentication
 Originally developed for disaster- and disruption-tolerant

Wi-Fi system for disaster-affected areas. (COMPSAC 2013)
 User (client) authentication is possible locallyby using EAP-TLS.

Issuer’s
private key

IssuerClient certificate
IssuerUser nameissue Certificate
User attributes
Signature

Signature verification for authentication.
User attributes for authorization.
Issuer’s
public key

Issuer’s
public key

Local RADIUS

Local RADIUS

APsAPsSite A
userSite B442

2021/12/16

Local authentication in In‐Flight Wi‐Fi A limited number of operator groups, such as airline

alliances, provide CA certificates and issue client certificates.
 A challenge exists in secure operation and handling of theCA certificates as many aircrafts are carrying them.
(detailed architecture design is in progress)

Operator A

Operator B

Operator E
In-Flight system

CA certificates for
EAP-TLS AuthN.

Local AAA serverwith Online Sign-Up(OSU) system

55Summary We have analyzed some prospective use cases of In-Flight

Wi-Fi and technical challenges to realize them.
 We have developed an adaptation of the certificate-based
local authentication method to the In-Flight Wi-Fi system.
 Roaming is possible, accepting user credentials fromsome operators.
 A Proof-of-Concept system is under development.
 Some more refinements will be needed, especially insecure system operation and business perspectives.

Hope you enjoy much better In-Flight Wi-Fi
in the near future.
663