Use Obfuscation to Improve the Size, Performance, and Security of Your J2ME Applications

Use Obfuscation to Improve the Size, Performance, and Security of Your J2ME Applications

bfuscate. According to the Merriam-Webster dictionary, obfuscate is a transitive verb meaning to darken, to make obscure or to confuse. In the software engineering business, obfuscation refers to “the deliberate act of nondestructively changing either the source code of a computer program or machine code when the program is in some compiled or binary form, so that it is not easy to understand or read.” Evidently, the author of this last definition must have seen some of my late-night code and decided that the adjective “deliberate” should be added to the definition lest someone mistake plain-old poor quality coding for obfuscated code. All kidding aside, obfuscation can be a serious tool in Java programming.

In J2ME, obfuscation can help protect applications that are deployed to millions of devices. Importantly, but often forgotten, obfuscation can also help developers with some other equally important issues?namely application size and performance.

These two issues are especially sticky when you’re developing for small mobile devices. However, though this article deals strictly with Micro Edition apps, most Java applications could stand to take advantage of the better security, smaller footprint, and improved performance obfuscation provides. You’ll find out what obfuscation does to J2ME code and why more developers should use obfuscation when delivering applications. You’ll also look at how tools and IDE’s provide obfuscation and see that not all obfuscators are created equal (there are various obfuscation methods of which you may not have been aware).

Why Obfuscate?
There are three reasons why you should consider obfuscation:

  1. Protection of intellectual property
  2. Footprint reduction
  3. Improve runtime performance

Protection of Intellectual Property
You’ve just created that killer J2ME application. You made a deal with a device manufacturer to put your application on millions of cell phones. With your application literally in the hands of so many people, how do you protect your intellectual property? If you think it takes special tools and training to reverse engineer your application, think again. Look inside your Java SDK bin directory. That javap.exe tool in the bin directory is a Java class file dissassembler?provided with the freely available SDK download. Getting a hold of your intellectual property is as easy as getting a hold of your class files and running:

	javap com.mycompany.KillerAppMidlet

Obfuscators help protect your property and make it harder to decompile code. The key and operative words in protection are “make it harder.” Obfuscation is not encrypting your intellectual property with crypto. It only makes the code that comes out of a decompiler like javap.exe harder&3151;often much harder?to understand and reverse engineer. Most of the obfuscator vendors will use the term “nearly impossible” when referring to the ability to reverse engineer code that has been obfuscated with their tool. While nearly impossible is good enough for most applications, it shouldn’t be confused with completely secure.

Footprint Reduction
Somewhere in your object-oriented training, you were probably taught to try to name packages, classes, methods, and fields after the real world things they represented. Instead of names like h, i, and j programmers have opted for names like, bank_account, getInterest, and interest_level. Though this naming convention is much more human readable and much easier to later maintain or modify, it turns out that all this “natural” naming tends to bloat the byte code that ultimately goes on the devices. Just how much bloat? Results are going to vary depending on your code (how it was written, how much of it is public vs. private, etc.) and what obfuscation tool is used and how it is configured to output code. In a non-scientific experiment, I used NetBeans 4.1 to build four different projects with NetBeans obfuscator on (NetBeans used ProGaurd’s obfuscator) and off. Table 1 shows the results.



Non-obfuscated jar size

Obfuscated jar size

% Reduction


Demo MIDlet Suite provided with WTK 2.2




Obex demo

Demo of Object Exchange provided with WTK 2.2




Web Service Client

J2ME WS client from




Stock Quote Suite

J2ME Stock Quote MIDlet demo from




Table 1. Four different projects built using the NetBeans obfuscator.

As you can see, some tools report as much as 70 percent reduction and the overall results suggest that 30-40 percent is normal for most applications. While you cannot always expect to reap a 40 percent reduction in your application, there is a good chance that an obfuscator is going to get you a significant chunk of space back. This has the impact of making it easier to obtain your application over the air and the application will load into memory faster when executed. Or, use the new-found space to build even more features into that killer application.

Improve Runtime Performance
This last benefit, again, depends on your choice in obfuscator and your code structure/functionality. However, several obfuscation vendors report that their techniques of obfuscation actually help improve the performance of the application. In some cases, the performance is improved by as much as 30 percent. PreEmptive Solutions‘ DashO product claims to use “its comprehensive analysis to provide clues to Java runtimes so they can work better.”

In fact, a new set of tools is growing up around the ideas offered by traditional obfuscators. Products such as Innaworks’ mBooster and J2ME Polish offer tools that offer to help optimize your J2ME applications beyond obfuscation.

What Does an Obfuscator Do?
In general, an obfuscator changes the byte code (the code stored in your .class files). What the obfuscator changes and how it determines what to change depends on the obfuscator implementation. There are many obfuscators and each use a variety of byte code transforming methods.

Additionally, obfuscation has changed over time. The first obfuscators (known generally as first generation obfuscators) simply changed the package, class, method, field, and variable names of your code to meaningless strings and removed any comments or debugging information. In a simplified example, all objects get transformed to simple x objects. Second generation obfuscators change the actual control flow (loops, conditionals, etc.). As another simple example, an obfuscator could take a simple statement like acct.setBalance(newBalance) and wrap it with a conditional:

	if (x=0) then {		acct.setBalance(newBalance);	} 	else{		//do something else	}	

The x=0 condition may always be true and the else portion of the statement may never get executed, but it’s tough for someone looking at decompiled code to know that. The runtime outcome of control-modified code should be the same, but tracing the functionality inside a program where the control has been modified is much tougher. Finally, there is data obfuscation whereby actual data structures are altered to further confuse anyone working with decompiled code. Again, a simple example includes increasing or decreasing the size of an array that is used in the code.

Obfuscator vendors today use a combination of these methods and other proprietary methods as well. Hongying Lai has written an excellent and often-referenced paper documenting some of the obfuscation methods and comparing several Java obfuscators that were on the market at the time the article was written in February 2001.

One more thing with regard to obfuscation and J2ME CLDC applications is the consideration of obfuscation before or after preverification. Recall that in limited devices, byte code verification of classes is usually too big of an operation to be done on the devices, so class files are “preverified” or annotated with byte code “properties” when the application is built and readied for deployment. The KVM on a J2ME CLDC device checks the class files for the preverification “properties.”

So, how does obfuscation that also modifies the byte codes affect this process? In most cases, obfuscation will be accomplished prior to the preverification step of your development build process. In this case, the obfuscated code is preverified and, when deployed, the KVM is none the wiser. Some tools offer options to obfuscate after preverification. This requires the preverification tool to also update the byte code properties so as not to invalidate the information already inserted by the preverification process.

Obfuscation Warnings
Obfuscation is a helpful tool to reduce the size of a deployed application, prevent outsiders from stealing your work, and possibly making your application perform better. However, nothing in software engineering comes for free and you should also be aware of some potential issues when obfuscating your code.

First, make sure you thoroughly test your obfuscated code. The goal of obfuscation is to scramble your application enough to make decompiling and understanding your application difficult. Sometime, the obfuscator goes a bit too far. Today’s products are good, but occasionally there are cases where the obfuscator stumbles on unforeseen code or the user is not aware of the various coding rules and configuration settings available with most obfuscators and the result is code that will not run when deployed to the device.

Platform independence may be compromised using obfuscation. For example, depending on the implementation, an obfuscator that knows about all the rich features in Java 5.0 may generate code that will not work on lesser JVMs.

Use of reflection tends to be one of the biggest obstacles in obfuscation. If you use a lot of reflection in your application, confer with the obfuscation vendor on potential issues and, in some cases, tips and tricks on how to avoid issues when the obfuscator comes in contact with reflective code.

Some methods of obfuscation actually increase the size of the application and/or reduce performance. In an exaggerated case, imagine what would happen if each line of code was surrounded by psuedo-conditional statements to effect control obfuscation? Check the size and performance of your obfuscated code to insure you are getting the benefits of obfuscation and not suffering from the opposite.

Obfuscation Implementation
Turn to your favorite Internet search and type “Java Obfuscation” and you will find dozens of obfuscators. Click here for a list of obfuscators to get you going.

Two of the most popular open source obfuscators are ProGuard and RetroGuard. On the commercial side, PreEmptive Solution’s DashO and Zelix KlassMaster Java Obfuscator are both well-touted Java obfuscators that also seem to understand and document special J2ME issues associated with obfuscation.

Most of the well known IDEs also offer built in obfuscators. NetBeans 4.1 with Mobility Pack comes with the open source ProGuard obfuscator already built in. In fact, obfuscation can be made part of the normal build process. Right click on any J2ME project in NetBeans and request properties from the resulting menu option. In the Properties window, one of the build options is “Obfuscating.” You have a slide bar dial that allows you to turn obfuscation on and off and to set the level of obfuscation when on (see Figure 1). A setting of two causes just private fields and methods to be obfuscated while a setting of nine causes “everything except public methods of MIDlet classes” to be obfuscated.

Figure 1. NetBeans Obfuscation Configuration: Obfuscation is easily made part of the build process by simply setting the level of obfuscation in the project properties.
Figure 2. Stubs for Obfuscators: When not immediately available, most IDEs provide the means to add an Obfuscator, as do Eclipse and the Wireless Toolkit. The Wireless Toolkit is shown here.

Both EclipseME and the J2ME Wireless Toolkit (now called the Sun Java Wireless Toolkit with release 2.3) are equipped to use the ProGuard obfuscator as well, but ProGuard must be downloaded and configured separately. Help with how to configure the obfuscator with the Wireless Toolkit is available here.

Obfuscating the Obvious
No, obfuscation is not the panacea solution for all J2ME problems. In some cases, because the IDEs are getting much better at helping us take advantage of all available development improvement options, you may already be obfuscating and you didn’t even know it. If so, great! Now you might also explore what obfuscator you are using and how you have it configured to give you optimal results.

As with all tools, a little research and some trial/error may be in order. But in J2ME, when something offers the promise of a smaller footprint, faster provisioning, possible performance enhancements, and better intellectual property security, I am hard pressed to find a reason not to at least explore it.



Share the Post:
Poland Energy Future

Westinghouse Builds Polish Power Plant

Westinghouse Electric Company and Bechtel have come together to establish a formal partnership in order to design and construct Poland’s inaugural nuclear power plant at

EV Labor Market

EV Industry Hurting For Skilled Labor

The United Auto Workers strike has highlighted the anticipated change towards a future dominated by electric vehicles (EVs), a shift which numerous people think will

Soaring EV Quotas

Soaring EV Quotas Spark Battle Against Time

Automakers are still expected to meet stringent electric vehicle (EV) sales quotas, despite the delayed ban on new petrol and diesel cars. Starting January 2023,

Affordable Electric Revolution

Tesla Rivals Make Bold Moves

Tesla, a name synonymous with EVs, has consistently been at the forefront of the automotive industry’s electric revolution. The products that Elon Musk has developed

Poland Energy Future

Westinghouse Builds Polish Power Plant

Westinghouse Electric Company and Bechtel have come together to establish a formal partnership in order to design and construct Poland’s inaugural nuclear power plant at the Lubiatowo-Kopalino site in Pomerania.

EV Labor Market

EV Industry Hurting For Skilled Labor

The United Auto Workers strike has highlighted the anticipated change towards a future dominated by electric vehicles (EVs), a shift which numerous people think will result in job losses. However,

Soaring EV Quotas

Soaring EV Quotas Spark Battle Against Time

Automakers are still expected to meet stringent electric vehicle (EV) sales quotas, despite the delayed ban on new petrol and diesel cars. Starting January 2023, more than one-fifth of automobiles

Affordable Electric Revolution

Tesla Rivals Make Bold Moves

Tesla, a name synonymous with EVs, has consistently been at the forefront of the automotive industry’s electric revolution. The products that Elon Musk has developed are at the forefront because

Sunsets' Technique

Inside the Climate Battle: Make Sunsets’ Technique

On February 12, 2023, Luke Iseman and Andrew Song from the solar geoengineering firm Make Sunsets showcased their technique for injecting sulfur dioxide (SO₂) into the stratosphere as a means

AI Adherence Prediction

AI Algorithm Predicts Treatment Adherence

Swoop, a prominent consumer health data company, has unveiled a cutting-edge algorithm capable of predicting adherence to treatment in people with Multiple Sclerosis (MS) and other health conditions. Utilizing artificial

Personalized UX

Here’s Why You Need to Use JavaScript and Cookies

In today’s increasingly digital world, websites often rely on JavaScript and cookies to provide users with a more seamless and personalized browsing experience. These key components allow websites to display

Geoengineering Methods

Scientists Dimming the Sun: It’s a Good Thing

Scientists at the University of Bern have been exploring geoengineering methods that could potentially slow down the melting of the West Antarctic ice sheet by reducing sunlight exposure. Among these

why startups succeed

The Top Reasons Why Startups Succeed

Everyone hears the stories. Apple was started in a garage. Musk slept in a rented office space while he was creating PayPal with his brother. Facebook was coded by a

Bold Evolution

Intel’s Bold Comeback

Intel, a leading figure in the semiconductor industry, has underperformed in the stock market over the past five years, with shares dropping by 4% as opposed to the 176% return

Semiconductor market

Semiconductor Slump: Rebound on the Horizon

In recent years, the semiconductor sector has faced a slump due to decreasing PC and smartphone sales, especially in 2022 and 2023. Nonetheless, as 2024 approaches, the industry seems to

Elevated Content Deals

Elevate Your Content Creation with Amazing Deals

The latest Tech Deals cater to creators of different levels and budgets, featuring a variety of computer accessories and tools designed specifically for content creation. Enhance your technological setup with

Learn Web Security

An Easy Way to Learn Web Security

The Web Security Academy has recently introduced new educational courses designed to offer a comprehensible and straightforward journey through the intricate realm of web security. These carefully designed learning courses

Military Drones Revolution

Military Drones: New Mobile Command Centers

The Air Force Special Operations Command (AFSOC) is currently working on a pioneering project that aims to transform MQ-9 Reaper drones into mobile command centers to better manage smaller unmanned

Tech Partnership

US and Vietnam: The Next Tech Leaders?

The US and Vietnam have entered into a series of multi-billion-dollar business deals, marking a significant leap forward in their cooperation in vital sectors like artificial intelligence (AI), semiconductors, and

Huge Savings

Score Massive Savings on Portable Gaming

This week in tech bargains, a well-known firm has considerably reduced the price of its portable gaming device, cutting costs by as much as 20 percent, which matches the lowest

Cloudfare Protection

Unbreakable: Cloudflare One Data Protection Suite

Recently, Cloudflare introduced its One Data Protection Suite, an extensive collection of sophisticated security tools designed to protect data in various environments, including web, private, and SaaS applications. The suite

Drone Revolution

Cool Drone Tech Unveiled at London Event

At the DSEI defense event in London, Israeli defense firms exhibited cutting-edge drone technology featuring vertical-takeoff-and-landing (VTOL) abilities while launching two innovative systems that have already been acquired by clients.

2D Semiconductor Revolution

Disrupting Electronics with 2D Semiconductors

The rapid development in electronic devices has created an increasing demand for advanced semiconductors. While silicon has traditionally been the go-to material for such applications, it suffers from certain limitations.

Cisco Growth

Cisco Cuts Jobs To Optimize Growth

Tech giant Cisco Systems Inc. recently unveiled plans to reduce its workforce in two Californian cities, with the goal of optimizing the company’s cost structure. The company has decided to

FAA Authorization

FAA Approves Drone Deliveries

In a significant development for the US drone industry, drone delivery company Zipline has gained Federal Aviation Administration (FAA) authorization, permitting them to operate drones beyond the visual line of

Mortgage Rate Challenges

Prop-Tech Firms Face Mortgage Rate Challenges

The surge in mortgage rates and a subsequent decrease in home buying have presented challenges for prop-tech firms like Divvy Homes, a rent-to-own start-up company. With a previous valuation of

Lighthouse Updates

Microsoft 365 Lighthouse: Powerful Updates

Microsoft has introduced a new update to Microsoft 365 Lighthouse, which includes support for alerts and notifications. This update is designed to give Managed Service Providers (MSPs) increased control and

Website Lock

Mysterious Website Blockage Sparks Concern

Recently, visitors of a well-known resource website encountered a message blocking their access, resulting in disappointment and frustration among its users. While the reason for this limitation remains uncertain, specialists