White Paper: Understanding security on the wireless Internet

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White Paper: Understanding security on the wireless Internet

How WAP security is enabling the rapid development of wireless e-commerce applications for today and tomorrow

Introduction

With the advent of e-commerce and e-banking, the Internet has changed the way many people purchase goods and manage their finances. Online trading, banking and shopping are available today to millions of Internet users. These services are now emerging on the wireless Internet, allowing subscribers to access bank accounts, trade stocks and purchase goods right from the screen of their wireless phone. This new avenue onto the Internet has been made possible by the Wireless Application Protocol (WAP), a de facto standard developed by the WAP Forum, a group of over 200 telecommunications and software companies. According to Strategy Analytics, there will be over 525 million WAP-enabled handsets in the marketplace by the year 2003.

WAP has stimulated application development by providing a common, secure protocol that allows applications to be written for use across existing wireless networks. Hundreds of applications that take advantage of this common application environment are now available. Many of these applications use WAP's security mechanism to ensure that transactions over the wireless Internet are safe and secure. Examples include wireless banking from Bank of Montreal, wireless stock trading from Ameritrade and Charles Schwab Canada, and wireless e-commerce from Amazon.com.

This paper explains the WAP security model and the WTLS mechanism, which provide a safe and secure environment for wireless Internet transactions today. It explains the key issues that any data security system must address and it describes how the WAP model addresses these issues. It also presents ideas for future improvements that the WAP Forum is considering for the next generation of WAP security.

The wireless Internet is already here

Wireless Internet access represents the next wave of the Internet. This trend is being spurred by the mobile phone industry's widespread support of the Wireless Application Protocol. By enabling WAP applications, a full range of wireless devices, including mobile phones, smartphones, PDAs and handheld PCs, gain a common method for accessing Internet information.

Strategy Analytics has reported that in 2003, 95 per cent of all handsets shipped will include WAP support. According to the Strategis Group, there are more than 32 million professional mobile data users in the US marketplace today and demand in this segment will continue to grow. With expanding subscriber bases and demand for new wireless data services driving phone sales, operators and manufacturers expect increased revenues from the sale of wireless Internet services and devices.

Analysts expect dynamic growth in the mobile market, with a forecast of more than one billion mobile phones in use within the next three to four years. According to Gartner Group, mobile phones are expected to be the most common client device accessing the Internet worldwide by 2005. Ovum has reported that smartphones and data-centric terminals will account for as much as two-thirds of the estimated $67 billion handset market in 2004.

All of these statistics demonstrate the enormous demand for wireless Internet services and applications. WAP enables rapid application deployment and provides access to the broadest consumer base possible because WAP was designed to operate on top of any type of wireless data network. Whether network operators are deploying CDMA, CDPD, GPRS, GSM, iDEN, PDC or TDMA data solutions, application providers can reach subscribers across multiple operator networks with a single application.

Sparked by an open, web-based protocol, network operators, handset manufacturers and content developers have all implemented solutions that have led to a groundswell of support for WAP deployments around the world. Applications exist today to view a variety of web content, manage email from the handset and gain better access to network operators' enhanced services. Beyond these information services, content providers are now developing solutions for the latest Internet opportunity - wireless e-commerce.

Recently, Ameritrade made its service WAP-capable for US mobile phone users. Thomas K. Lewis, Jr., co-chief executive officer of Ameritrade Holding Corporation, noted in a recent press release that the addition of wireless web access is another step in Ameritrade's continuing effort to extend the ability of its customers to invest when and how they choose. "Ameritrade is a customer-oriented organisation," Lewis said. "We know that our customers want to be empowered to act on their investment decisions at any given moment."

As more subscribers demand WAP services, the need for wireless Internet security will continue to grow. In the mid 1990s, a push to provide strong encryption occurred in the hopes of fostering electronic commerce. For years, the "next killer app" hype surrounded electronic commerce. But until Secure Sockets Layer (SSL) and encryption became widespread de facto security standards, electronic commerce was only a curiosity, not a mass-market opportunity. By 1998, the security infrastructure was in place, triggering a dramatic increase in electronic commerce transactions. 1998 became the year of e-commerce, with Internet operations challenging traditional "bricks and mortar" operations for the first time. Now the industry is poised to take its next big leap forward into the wireless world.

In June 1999, the WAP Forum formally approved WAP Version 1.1. WAP 1.1 includes the WTLS specification, which defines how Internet security is extended to the wireless Internet. WTLS is poised to do for the wireless Internet what SSL did for the Internet - open whole new markets to e-commerce opportunities. Network operators providing application developers and end users with effective WAP-based wireless security are capitalising on this emerging trend.

Security on the Internet

A first step to understanding how the WAP security model works is to review how SSL security makes e-commerce secure over the Internet. Today's security solutions keep information away from individuals who should not have access to confidential or financial data. Security protects mission-critical information that can be used against a corporation or used to create fraudulent transactions. Additionally, security provides peace of mind, ensuring that individuals and institutions are comfortable conducting business and exchanging information online.

There are four different concerns that a security system can address: privacy, integrity, authenticity and non-repudiation.

Privacy ensures that only the sender and the intended recipient of an encrypted message can read the contents of that message. To guarantee privacy, a security solution must ensure that no one can see, access or use private information, such as addresses, credit card information and phone numbers, as it is transmitted over the Internet.

Integrity ensures the detection of any change in the content of a message between the time it is sent and the time it is received. For example, when a user instructs a bank to transfer $1,000 from one account to another, integrity guarantees that the account numbers and dollar amount in the user's message cannot be altered without the bank or the user noticing. If the message is altered in any way during transmission, the security system must have a way of detecting and reporting this alteration. In many systems, if an alteration is detected, the receiving system requests that the message be re-sent.

Authentication ensures that all parties in a communication are who they claim to be. Server authentication provides a way for users to verify that they are really communicating with the website to which they believe they are connected. Client authentication ensures that the user is who they claim to be. Examples of authentication in the real world include presenting a driving licence to verify that a consumer writing a cheque is the person named on that cheque, and presenting a corporate photo ID to prove that a telephone technician really works for the telephone company.

Non-repudiation provides a method to guarantee that a party to a transaction cannot falsely claim that they did not participate in that transaction. In the real world, handwritten signatures are used to ensure this. When a consumer writes a cheque, presenting a driving licence ensures the identity of the writer (authentication), while the signature on the cheque ensures that the consumer was in fact present and agreed to write the cheque (non-repudiation).

Over the Internet, the Secure Sockets Layer (SSL) protocol, digital certificates and either user name/password pairs or digital signatures are used together to provide all four types of security. The following explains these different techniques.

Public key cryptography is an encryption method that is a key component of SSL. It uses pairs of keys and mathematical algorithms to convert clear text into encrypted data and back again. The pair consists of a registered public key and a private key that is kept secret by its owner. A message encrypted with the public key can be decrypted only by someone with the private key. Likewise, a message encrypted with the private key can be decrypted only by someone with the public key.

Public key cryptography uses very advanced algorithms to encrypt small amounts of information but is impractical for encrypting large quantities of data. Faster bulk encryption algorithms use a shared secret key between the communicating parties to encrypt most secure messages on the Internet. These algorithms are extremely difficult to decode when the shared secret key contains a large number of bits. SSL uses public key cryptography to exchange this key at the beginning of a secure Internet conversation, thus ensuring that it remains a secret for the duration of the conversation.

SSL uses public key cryptography, bulk encryption algorithms and shared secret key exchange techniques to provide privacy over the Internet. To provide integrity, SSL uses hashing algorithms that create a small mathematical fingerprint of a message. If any part of the message is altered, it will not match its fingerprint when the message is checked at the receiving end. In this case, the sender is asked to re-send the message.

Because anyone can generate key pairs, it is possible for a malicious party to put up an impostor website and then falsify information in a transaction by providing a public key to a user. To prevent this kind of fraud, digital certificates are used to provide an authenticated way to distribute public and private keys. Digital certificates are also used to authenticate the parties of an Internet conversation so that users and content providers can both be confident they know with whom they are communicating.

There are two different kinds of digital certificates - server certificates and client certificates. Server certificates are used to authenticate that a web server is what it claims to be. Client or personal certificates are used to authenticate the identity of an individual user on the Internet. Both types of certificates include the certificate holder's identity and public key, and other information used to authenticate the certificate. Most importantly, the certificate is itself encrypted with the private key of a certificate authority, creating an independent binding of the public key and the certificate holder. Third party companies like VeriSign and RSA Security operate as certificate authorities, providing a respected, independent resource to issue keys and certificates to their holders.

When a web browser requests a secure conversation with a web server, the server provides the browser with its server certificate. The browser authenticates the web server by confirming that a valid certificate authority encrypted the certificate. It then uses the public key stored in the certificate to encrypt a shared secret key to send to the web server. The shared secret key is used to encrypt the rest of the conversation. By using a server certificate, the web server and browser can have a secure conversation that is private and authenticated, with guaranteed integrity.

Note that in this example only the server has been authenticated. Client certificates can be used to authenticate a user to the web server but today, most web applications rely on a simple user name and password to authenticate the user of the browser client.

The remaining issue to address is non-repudiation. As with client authentication, most web applications today simply rely on the entry of a user name and password to provide non-repudiation. Applications can request a digital signature from a client, which requests that the user specifically authorise a transaction. The authorisation is then encrypted utilising the user's private key from their client certificate. Not surprisingly, a digital signature is analogous to a real signature on a cheque and serves the same purpose. So far though, the adoption of client certificates for individuals on the Internet has been slow.

Good network security solutions require that content providers and clients manage and maintain their digital certificates and other security information carefully. Public Key Infrastructure (PKI) solutions help companies manage this information so that it is secure and easy to organise. PKI contains three common functional components: the certificate authority to issue certificates (in-house or out-sourced); a repository for keys, certificates and certificate revocation lists on an LDAP-enabled directory service; and a management function, typically implemented via a management console. Additionally, PKIs can provide key recovery in case a user loses their private key due to a hardware failure or other problem.

Different combinations of all of these security techniques are used for different applications, depending on which forms of security are important and the degree to which the solution needs to be balanced with the convenience for the user. For example, certificate-based client authentication and non-repudiation are not widely used on the web today because most users don't want to be bothered with the administrative tasks of obtaining and safely maintaining a client certificate.

Security in a WAP environment

There are three parts to the WAP security model. First, the WAP gateway simply uses SSL to communicate securely with a web server, ensuring privacy, integrity and server authenticity.

Second, the WAP gateway takes SSL-encrypted messages from the web and translates them for transmission over wireless networks using WAP's WTLS security protocol. Messages from the handset to the web server are likewise converted from WTLS to SSL. In essence, the WAP gateway is a bridge between the WTLS and SSL security protocols.

The need for translation between SSL and WTLS is incurred by the very nature of wireless communications: low bandwidth transmissions with high latency. Because SSL was designed for desktop and wired environments with robust processing capabilities connected to a relatively high-bandwidth and low-latency Internet connection, cell phone users would be disappointed by the delays required to process SSL transactions. Furthermore, to put SSL functionality into handsets would raise cell phone costs and destroy the low-cost pricing paradigm that is driving industry growth.

WTLS was specifically designed to conduct secure transactions without requiring desktop levels of processing power and memory in the handset. WTLS processes security algorithms faster by minimising protocol overhead and enables more data compression than traditional SSL solutions. As a result, WTLS can perform security well within the constraints of a wireless network. These optimisations mean that smaller, portable consumer devices can now communicate securely over the Internet.

The translation between SSL and WTLS takes milliseconds and occurs in the memory of the WAP gateway, allowing for a virtual, secure connection between the two protocols. Suppliers of the WAP gateway and network operators take every measure possible to keep the WAP gateway itself secure by:

Ensuring that the WAP gateway never stores decrypted content on secondary media

Using a process of decryption/re-encryption that is security conscious and optimised for speed so that the unencrypted content of a message is erased from the volatile internal memory of the WAP gateway as quickly as possible

Securing the WAP gateway physically so that only authorised administrators have access to the system console

Limiting administrative access to the WAP gateway so that it is not available to any remote site outside the carrier's firewall

Applying all other security precautions used to protect billing systems and the Home Location Register to the WAP gateway

On the wireless side of the transaction, the WAP gateway uses WTLS to provide privacy, integrity and authentication between itself and the WAP browser client. It is based on the Internet standard security protocol TLS 1.0, which, in turn, is based on SSL 3.0, providing the functionality of a strong Internet security standard over a wireless airlink. WTLS goes beyond TLS 1.0 by incorporating new features such as datagram support, optimised handshake and dynamic key refreshing.

Although the WAP security model does not call for non-repudiation or client authentication, a particular gateway provider's implementation can provide this with the use of client certificate and digital signature technology. Applications can implement client authentication and non-repudiation by following the standard web development practice of requiring users to enter a username and password.

WTLS and the WAP security model provide an extremely secure solution that leverages the best technologies from the Internet and wireless worlds. When the WAP gateway is deployed in an operator environment according to standard operator security procedures, subscribers and content providers can be assured that their personal data and applications are secure.

Next generation WAP security

The current WAP security model requires a strong relationship between the network operator and the content provider to implement the most secure solutions possible. The WAP Forum has recognised that as the market for highly secure applications increases, a more flexible and extensible solution will be needed. When working across many different wireless networks, application developers must be assured that their content remains encrypted from the time it leaves their application server until it arrives at the WAP handset. Phone.com has been participating in the WAP process to develop this more advanced security solution, which must address the enterprise's need for higher security and the operator's need for proper integration with WAP gateways in the wireless network.

Solutions are now coming to market before the WAP Forum has established a standard approach to providing end-to-end secure content. Besides being proprietary, these solutions promote installing a WAP Gateway at a content provider or in an enterprise. Since WAP Gateways were designed for use in an operator's network, this creates a number of difficulties for content providers, subscribers and wireless network operators.

Operating a WAP gateway at the content source places a burden on the content provider to maintain a system that is compatible with a variety of network protocols and SMSCs. For each network and SMSC combination, the content provider will have to support a different configuration on their gateway. This goes against one of the original goals of the WAP Forum to provide content solutions that are network independent and increases the effort required for the content developer to deliver services to the wireless Internet.

Content providers are burdened with handset provisioning and activation issues. The content site must either limit their offering to a small number of handset models or take on the burden of supporting a broad array of devices.

Because these solutions are proprietary, they do not work across all WAP handsets. In some cases, they work with only a single handset model, limiting the subscriber population that content providers can reach.

Subscribers will find it difficult to switch between an operator's network-based WAP gateway and the content provider's or enterprise's gateway. This manual switching requires changing raw handset parameters each time the subscriber wishes to contact a different site. Furthermore, when the subscriber experiences difficulty, both the network operator and the content provider will experience increased support costs.

Subscribers will have more difficulty getting quality of service issues resolved. Where does a subscriber call to report a problem with a handset that was supplied by a content provider and is connecting to the content provider's WAP gateway but service is being provided by a network operator? Do they call the operator? The content provider? The handset manufacturer?

Operators must trust equipment operated outside their network that interacts closely with their network elements. This can lead to traffic management problems, e.g., systems out of their control could flood their networks with SMS messages. This has an adverse effect on the content provider as well because their system must compete with others like it for an unknown amount of network resources, which may lead to poor quality of service for the subscriber.

A solution intended for enterprises and content sites should be designed to meet their unique needs and address the real issues of offering seamless, quality service that integrates well with an operator's WAP gateway. A well-designed enterprise WAP solution should:

Insulate the content site from the implementation details of the wireless network so that applications remain network and SMSC-independent

Leverage the existing activation and provisioning systems in the operator's network to shield content developers from these issues

Enable access from any WAP-compatible handset

Provide a simple, transparent way for subscribers to access enterprise WAP sites. It should be as easy to access one of these sites as it is today to access a standard WAP content site

Make it easy to identify whether a quality of service issue lies with the operator's network systems or the content provider's web server. This allows network operators and content providers to ensure customer satisfaction by helping to resolve service issues quickly

Allow the network WAP gateway to work closely with the enterprise WAP solution so that network resources can be properly utilised and shared across the wireless Internet subscriber population.

Allow application developers to integrate WAP technology that can encrypt content using WTLS and send it through the Internet to operators' networks

Offer the proper interfaces to integrate with the content provider's existing Public Key Infrastructure (PKI) solution, allowing for ease of integration into the provider's existing e-commerce systems

Provide a clear upgrade path from existing WTLS 1.1-compatible applications to this new grade of WAP security

Enabling content developers to build solutions that are network independent and secure from end-to-end is essential. With a high-quality, well-designed solution that integrates seamlessly with network WAP gateway solutions, both content developers and network operators will benefit from the continued growth of value-added subscriber applications.

WAP security: today and tomorrow

Application providers and wireless network users should feel confident that today's transactions leverage the best security provisions that SSL offers through the robust WTLS implementation. Already, key Internet applications for handsets have been deployed, including e-banking, stock trading, e-commerce, and other exchanges of private and mission-critical data.

With WTLS optimised to ensure transactions are conducted in a secure and user-friendly way, and WAP-capable handsets reaching the market, subscribers are beginning to embrace wireless e-commerce in the same fashion that consumers have adopted wired e-commerce over the last 18 months. As application developers realise returns on WAP applications, the market is expected to grow rapidly, leading to a wealth of secure, wireless e-commerce applications. Application developers are further assured of their investment since the WAP Forum is already working to develop even more secure solutions for the future.

(c) 2000 Phone.com


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This was first published in March 2000

 

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