Advice on encrypting the class files so that it cannot be reverse engineer

Hi,
i will like to ask if there is any way where we can encrypt the class files so that people cannot use reverse engineering to modify the codes?
Thanks

tommickey wrote:
leeChaolan wrote:
Hi,
i will like to ask if there is any way where we can encrypt the class files so that people cannot use reverse engineering to modify the codes?
ThanksIn addition to what others said encryption is totally different from what you want.(called as 'obfuscation').Not necessarily. You could encrypt the class files, but then you would have to provide an unencrypted ClassLoader (and possibly Main if you didn't want to put the ClassLoader in the bootstrap classpath) that is capable of decrypting them. Then, someone could decompile this ClassLoader (obfuscated or not) and either simply take the decryption algorithm and decrypt the classes, or even easier, simply modify the ClassLoader to write out the decrypted class files itself.
So, why would you? ;-)

Similar Messages

How do I encrypt a data file so that only I can retrieve the info?

How do I encrypt a data file so that it cannot be read without the proper authority?
I have an application where the customer should not have access to the data I need to record for troubleshooting purposes. (there are industrial secrets I wish to protect) My plan is to record a datalog (currently I am producing a tab-delimited spreadsheet format) whenever the device is running and hide the files where they will probably not be found. But some sort of encryption or at least password protection would be better.
I've never tried to do this before, but thought it would be fairly easy. Maybe I'm just not looking in the right places.
Thanks
Solved!
Go to Solution.

Well, you could look into something like DES, Triple DES, AES, etc. There are libries floating around for these written in LabVIEW. I'm not sure about the cost though.
If you want a really simple way to protect your data, just invert all or some of the bits in each byte of your file. It is super simple and turns a nice ASCII text file into noise when read from a text file.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
Unofficial Forum Rules and Guidelines

Error while encrypting the xml file using asymmetric cipher...pls help

i am encryption the xml file using asymmetric cyper....
in one class , i am generating private key and public key using "RSA" algorithm..using 1024 byte initialization...
it is generating properly...
and after that in second class i am encrypting the xml file using "DESede" algorithm and i am using public key of above class..
but i am getting exceptione :
java.security.InvalidKeyException: Invalid key length: 162 bytes
at com.sun.crypto.provider.DESedeCipher.engineGetKeySize(DashoA6275)
at javax.crypto.Cipher.init(DashoA6275)
at XmlEncryption.getEncryptedData(XmlEncryption.java:147)
at XmlEncryption.encryptCompleteXmlFile(XmlEncryption.java:123)
at demoXmlEncApp.simulateBookSellersEnd(demoXmlEncApp.java:72)
at demoXmlEncApp.main(demoXmlEncApp.java:29)
so, what is that ?
i want to use RSA algo for key generatiion and DESede for cipher initialization .
is there any site for where source code of xml file encryption using asymmetric cipher is available?
pls, help me.....

Sachin,
What sabre150 is trying to explain to you, is that encrypting data (such as an XML file) is a 2-step process. In the first step, you generate a symmetric key (such as DES, 3DES, AES) and encrypt your file with this key (and the appropriate mode and padding).
In order to ensure that your encrypted data cannot be decrypted by unauthorized individuals, you now need to protect the symmetric key. Encrypting your symmetric key with another symmetric key does not solve the problem, since you have a chain of symmetric keys that need to be encrypted into infinity.
Cryptographers solve this problem by encrypting the symmetric key with an asymmetric key, such as as RSA. To perform this second step, you generate an RSA key-pair, encrypt the symmetric key you generated in step 1 with the Public key of the RSA key-pair, and give the recipient of the encrypted XML file, access to the Private key of the RSA key-pair as well as the encrypted symmetric key.
The recipient, then uses the RSA Private key to decrypt the symmetric key first, and then uses the "plaintext" symmetric key to decrypt the XML file.
What sabre150 was also attempting to explain to you, is the traditional way of transporting an encrypted "blob" that consists of data + symmetric key. With a modern key-management system, combining the two would be unnecessary.

How do I make a batch file if the .class file uses a foreign package?

I am trying to make an MS-DOS batch file using the bytecode file from the Java source file, called AddFields.java. This program uses the package BreezySwing; which is not standard with the JDK. I had to download it seperately. I will come back to this batch file later.
But first, in order to prove the concept, I created a Java file called Soap.java in JCreator. It is a very simple GUI program that uses the javax.swing package; which does come with the JDK. The JDK is currently stored in the following directory: C:\Program Files\Java\jdk1.6.0_07. I have the PATH environment variable set to the 'bin' folder of the JDK. I believe that it is important that this variable stay this way because C:\Program Files\Java\jdk1.6.0_07\bin is where the file 'java.exe' and 'javac.exe' are stored. Here is my batch file so far for Soap:
@echo off
cd \acorn
set path=C:\Program Files\Java\jdk1.6.0_07\bin
set classpath=.
java Soap
pause
Before I ran this file, I compiled Soap.java in my IDE and then ran it successfully. Then I moved the .class file to the directory C:\acorn. I put NOTHING ELSE in this folder. then I told the computer where to find the file 'java.exe' which I know is needed for execution of the .class file. I put the above text in Notepad and then saved it as Soap.bat onto my desktop. When I double click on it, the command prompt comes up in a little green box for a few seconds, and then the GUI opens and says "It Works!". Now that I know the concept of batch files, I tried creating another one that used the BreezySwing package.
After I installed my JDK, I installed BreezySwing and TerminalIO which are two foreign packages that make building code much easier. I downloaded the .zip file from Lambert and Osborne called BreezySwingAndTerminalIO.zip. I extracted the files to the 'bin' folder of my JDK. Once I did this, and set the PATH environment variable to the 'bin' folder of my JDK, all BreezySwing and TerminalIO programs that I made worked. Now I wanted to make a batch file from the program AddFields.java. It is a GUI program that imports two packages, the traditional GUI javax.swing package and the foreign package BreezySwing. The user enters two numbers in two DoubleField objects and then selects one of four buttons; one for each arithmetic operation (add, subtract, multiply, or divide). Then the program displays the solution in a third DoubleField object. This program both compiles and runs successfully in JCreator. So, next I moved the .class file from the MyProjects folder that JCreator uses to C:\acorn. I put nothing else in this folder. The file Soap.class was still in there, but I did not think it would matter. Then I created the batch file:
@echo off
cd \acorn
set path=C:\Program Files\Java\jdk1.6.0_07\bin
set classpath=.
java AddFields
pause
As you can see, it is exactly the same as the one for Soap. I made this file in Notepad and called it AddFields.bat. Upon double clicking on the file, I got this error message from command prompt:
Exception in thread "main" java.lang.NoClassDefFoundError: BreezySwing/GBFrame
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:12
4)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
Caused by: java.lang.ClassNotFoundException: BreezySwing.GBFrame
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:276)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
... 12 more
Press any key to continue . . .
I know that most of this makes no sense; but that it only means that it cannot find the class BreezySwing or GBFrame (which AddFields extends). Notice, however that it does not give an error for javax.swing. If I change the "set path..." command to anything other than the 'bin' folder of my JDK, I get this error:
'java' is not recognized as an internal or external command,
operable program or batch file.
Press any key to continue . . .
I know this means that the computer cannot find the file 'java.exe' which I believe holds all of the java.x.y.z style packages (native packages); but not BreezySwing or any other foreign packages. Remember, I do not get this error for any of the native Java packages. I decided to compare the java.x.y.z packages with BreezySwing:
I see that all of the native packages are not actually visible in the JDK's bin folder. I think that they are all stored in one of the .exe files in there because there are no .class files in the JDK's bin folder.
However, BreezySwing is different, there is no such file called "BreezySwing.exe"; there are just about 20 .class files all with names like "GBFrame.class", and "GBActionListener.class". As a last effort, I moved all of these .class files directly into the bin folder (they were originally in a seperate folder called BreezySwingAndTerminalIO). This did nothing; even with all of the files in the same folder as java.exe.
So my question is: What do I need to do to get the BreezySwing package recognized on my computer? Is there possibly a download for a file called "BreezySwing.exe" somewhere that would be similar to "java.exe" and contain all of the BreezySwing packages?

There is a lot of detail in your posts. I won't properly quote everything you put (too laborious). Instead I'll just put your words inside quotes (").
"..there are some things about the interface that I do not like."
Like +what?+ This is not a help desk, and I would appreciate you participating in this discussion by providing details of what it is about the 'interface' of webstart that you 'do not like'. They are probably misunderstandings on your part.
"Some of the .jar files I made were so dangerously corrupt, that I had to restart my computer before I could delete them."
Corrupt?! I have never once had the Java tools produce a corrupt Jar. OTOH, the 'cannot delete' problem might relate to the JRE gaining a file lock on the archive at run-time. If the file lock persisted after ending the app., it suggests that the JRE was not properly shut down. This is a bug in the code and should be fixed. Deploying as .class files will only 'hide' the problem (from casual inspection - though the Task Manager should show the orphaned 'java' process).
"I then turned to batch files for their simple structure and portability (I managed to successfully transport a java.util containing batch file from my computer to another). This was what I did:
- I created a folder called Task
- Then I copied three things into this folder: 1. The file "java.exe" from my JDK. 2. The program's .class file (Count.class). and 3. The original batch file.
- Then I moved the folder from a removable disk to the second computer's C drive (C:\Task).
- Last, I changed the code in the batch file...:"
That is the +funniest+ thing I've heard on the forums in the last 72 hours. You say that is easy?! Some points.
- editing batch files is not scalable to 100+ machines, let alone 10000+.
- The fact that Java worked on the target machine was because it was +already installed.+ Dragging the 'java.exe' onto a Windows PC which has no Java will not magically make it 'Java enabled'.
And speaking of Java on the client machine. Webstart has in-built mechanisms to ensure that the end user has the minimum required Java version to run the app. - we can also use the [deployJava.js|http://java.sun.com/javase/6/docs/technotes/guides/jweb/deployment_advice.html#deplToolkit] on the original web page, to check for minimum Java before it puts the link to download/install the app. - if the user does not have the required Java, the script should guide them through installing it.
Those nice features in deployJava.js are available to applets and apps. launched using webstart, but they are not available for (plain) Jar's or loose class files. So if 'ensuring the user has Java' is one of the requirements for your launch, you are barking up the wrong tree by deploying loose class files.
Note also that if you abandon webstart, but have your app. set up to work from a Jar, the installation process would be similar to above (though it would not need a .bat file, or editing it). This basic strategy is one way that I provide [Appleteer (as a downloadable ZIP archive)|http://pscode.org/appleteer/#download]. Though I side-step your part 1 by putting the stuff into a Jar with the path Appleteer/ - when the user expands the ZIP, the parts of the app. are already in the Appleteer directory.
Appleteer is also provided as a webstart launched application (and as an applet). Either of those are 'easier' to use than the downloadable ZIP, but I thought I would provide it in case the end user wants to save it to disk and transport the app. to a machine with no internet connection, but with Java (why they would be testing applets on a PC with no internet connection, I am not sure - but the option is there).
"I know that .jar and .exe files are out because I always get errors and I do not like their interfaces. "
What on earth are you talking about? Once the app. is on-screen, the end user would not be able to distinguish between
1) A Jar launched using a manifest.
2) A Jar launched using webstart.
3) Loose class files.
Your fixation on .bat files sounds much like the adage that 'If the only tool you have is a hammer, every job starts to look like a nail'.
Get over them, will you? +Using .bat files is not a practical way to provide a Java app. to the end user+ (and launching an app. from a .bat looks quite crappy and 'second hand' to +this+ user).
Edit 1:
The instructions for running Appleteer as a Jar are further up the page, in the [Running Appleteer: Application|http://pscode.org/appleteer/#application] section.
Edited by: AndrewThompson64 on May 19, 2009 12:06 PM

How to hide the source code from the .class file

Hi,
By some jad tool we can recompile the .class files and get the java file corresponding to it. How to protect it?
Anyone please help me..
Thanks & Regards,
N.Ravasankar

An obfuscator can for example rename classes, variables to meaningless names, like one-letter names. And it can make some bytecode that is hard to decompile or just makes the code less readable when decompiled. Some obfuscators might even be able to do something to the code that makes decompilers not work or incorrect decompile code.

Java.lang.AssertionError: WSDL not found in the class file "processes

Hi,
I am using WLI 10.3 workshop to build process application. I have designed one JPD which inturn call another process JPD. So i have used worklist process control to create the process and tried to access the process. When i am executing the code, i am getting below error message.
13-Jun-2011 14:13:00 o'clock BST> <Error> <WLI> <BEA-000000> <Exception processing processes.ISPSSQMsgLisnt
Java.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.bea.wli.knex.runtime.core.dispatcher.DispUnit.loadDispFile(DispUnit.java:219)
Truncated. see log file for complete stacktrace
Java.lang.AssertionError: WSDL not found in the class file "processes.ISPSSQMsgLisnt", annotated class = processes.ISPSSQMsgLisnt
--ClassAnnotations:
--Method Annotations:
--Field Annotations:
can't continue
at com.bea.wli.knex.runtime.jws.dispatcher.JwsDispClass.<init>(JwsDispClass.java:392)
at com.bea.wli.bpm.runtime.JpdDispClass.<init>(JpdDispClass.java:65)
at com.bea.wli.bpm.runtime.JpdDispClass.<init>(JpdDispClass.java:55)
at com.bea.wli.bpm.runtime.JpdDispFile.createPrimaryDispClass(JpdDispFile.java:382)
at com.bea.wli.knex.runtime.core.dispatcher.DispFile.<init>(DispFile.java:154)
Truncated. see log file for complete stacktrace
xception processing processes.ISPSSQMsgLisnt
ava.lang.reflect.InvocationTargetException
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at com.bea.wli.knex.runtime.core.dispatcher.DispUnit.loadDispFile(DispUnit.java:219)
at com.bea.wli.knex.runtime.core.dispatcher.DispUnit.<init>(DispUnit.java:153)
at com.bea.wli.knex.runtime.core.dispatcher.DispCache.ensureDispUnit(DispCache.java:628)
at com.bea.wli.knex.runtime.core.dispatcher.DispCache.ensureDispUnitForURI(DispCache.java:1029)
at com.bea.wli.knex.runtime.core.dispatcher.DispCache.ensureDispUnitForURI(DispCache.java:950)
at com.bea.wli.broker.JWSSubscriber.getDispClass(JWSSubscriber.java:231)
at com.bea.wli.broker.JWSSubscriber.getRequest(JWSSubscriber.java:184)
at com.bea.wli.broker.JWSSubscriber.doDispatch(JWSSubscriber.java:358)
at com.bea.wli.broker.JWSSubscriber.doDispatch(JWSSubscriber.java:348)
at com.bea.wli.broker.SubscriptionDispatcher.doDispatch(SubscriptionDispatcher.java:87)
at com.bea.wli.broker.MessageBroker$PrivilegedSubscriptionDispatcher.run(MessageBroker.java:179)
at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:363)
at weblogic.security.service.SecurityManager.runAs(Unknown Source)
at com.bea.wli.security.authentication.AuthenticationService.runAs(AuthenticationService.java:108)
at com.bea.wli.broker.MsgBrokerSecurityHelper.doDispatch(MsgBrokerSecurityHelper.java:231)
at com.bea.wli.broker.MessageBroker$PrivilegedSubscriptionDispatcher.doDispatch(MessageBroker.java:165)
at com.bea.wli.broker.MessageBroker.publishMessage(MessageBroker.java:984)
at com.bea.wli.mbconnector.jms.JmsConnMDB.publishMBMessage(JmsConnMDB.java:343)
at com.bea.wli.mbconnector.jms.JmsConnMDB.onMessage(JmsConnMDB.java:475)
at weblogic.ejb.container.internal.MDListener.execute(MDListener.java:466)
at weblogic.ejb.container.internal.MDListener.transactionalOnMessage(MDListener.java:371)
at weblogic.ejb.container.internal.MDListener.onMessage(MDListener.java:327)
at weblogic.jms.client.JMSSession.onMessage(JMSSession.java:4547)
at weblogic.jms.client.JMSSession.execute(JMSSession.java:4233)
at weblogic.jms.client.JMSSession.executeMessage(JMSSession.java:3709)
at weblogic.jms.client.JMSSession.access$000(JMSSession.java:114)
at weblogic.jms.client.JMSSession$UseForRunnable.run(JMSSession.java:5058)
at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:516)
at weblogic.work.ExecuteThread.execute(ExecuteThread.java:201)
at weblogic.work.ExecuteThread.run(ExecuteThread.java:173)
aused by: java.lang.AssertionError: WSDL not found in the class file "processes.ISPSSQMsgLisnt", annotated class = processes.ISPSSQMsgLisnt
--ClassAnnotations:
--Method Annotations:
--Field Annotations:
can't continue
at com.bea.wli.knex.runtime.jws.dispatcher.JwsDispClass.<init>(JwsDispClass.java:392)
at com.bea.wli.bpm.runtime.JpdDispClass.<init>(JpdDispClass.java:65)
at com.bea.wli.bpm.runtime.JpdDispClass.<init>(JpdDispClass.java:55)
at com.bea.wli.bpm.runtime.JpdDispFile.createPrimaryDispClass(JpdDispFile.java:382)
at com.bea.wli.knex.runtime.core.dispatcher.DispFile.<init>(DispFile.java:154)
at com.bea.wli.knex.runtime.jws.dispatcher.JwsDispFile.<init>(JwsDispFile.java:24)
at com.bea.wli.bpm.runtime.JpdDispFile.<init>(JpdDispFile.java:108)
... 34 more

Hi
Are you using wli process control?
That uses wsdl and could cause the issue.
I also saw couple of internal bugs CR264315 and CR288904 on the same issue on 9.2.
Since this is a wli issue could you post in the wli newsgroup to get more answers http://forums.bea.com/forum.jspa?forumID=2047 ?
Also you can open a BEA support case at http://support.bea.com and an wli support engineer would help you. Please refer to the Cr numbers above in your support case.
Thanks
Vimala

Whether to import the class file put in JAVA_TOP

I have put the java class file in JAVA_TOP. Now i want to access the method in that class from jsp, is it necessary to import the class file path in jsp. Without importing the class file path how can i access the method.
JSP Coding
<%@ page contentType="text/html;charset=windows-1252"%>
<%@ page import="java.*" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<title>
Hello World
</title>
</head>
<body>
<%
sample objsample = new sample();
%>
<b>
NAME : </b><input type="text" value="<%=objsample.getName()%>">
</body>
</html>
Class file
public class sample
public sample()
String name = "JOHN";
public String getName()
return name;
Pls help me

Hi,
For sys outs check the following log files:
<ORACLE_SOA_HOME>/opmn/logs/default_group~home~default_group~1.log
or
<ORACLE_SOA_HOME>/j2ee/home/log/home_default_group_1/system_*.log
Here server instance name is home, change it with your server instance name.
Dharmendra
http://soa-howto.blogspot.com

When using just the class files

I have passed my app over to someone else by just passing over the .class files and the dlls and a text file that I need to generate an id.
Everything seems to be working fine apart from generating the id number I get a blank dialog box with no id inside. Has anyone anyideas why??

Your question will be very hard to answer, because we don't have a clue how you create the id using the text file. Please explain how you do that, possibly post some source code.
Jesper

JNI generated header file does not match the class file

We have had a JNI project for many years and all has been fine. Within our libraries we have several classes that have inner enum classes.
Recently we have moved to JDK1.7. Up to now when JNI generated the methods where the signature used the inner enum class, and it was an oveloaded method, we would get something like the following as the signature:
Java_PackageName_ClassName_methodName_OuterClass_00024InnerEnum_2
And the class file result of the build would look like the following:
methodName(OuterClass$InnerEnum)
Since we have moved to JDK 1.7 the header file looks like the following:
Java_PackageName_ClassName_methodName_OuterClasss_InnerEnum_2
The class file is still the same, and because of that when we run the program we get an UnsatisfiedLinkError. I understand that this error is because the VM cannot find the implementation. So why JDK 1.7 generates a header file that does not match the class file?
Thank you in advance.

I don't have 1.6 to verify but your statements about what is generated for 1.7 for the header appear correct.
The 000024 represents the '$' and for 1.7 the inner class is still named using '$'. So for example after compiling in 1.7 the inner class file is named the following...
MyClass$InnerEnum.class
So a one to one conversion should have kept the 000024 (presuming it does in fact do it that way in 1.6.)
You might want to look at the release notes for 1.7.
If you need a solution you could add a post javah step that renames the file.

How to protect the class files inside jar file.

Hi Group,
pls help me.
my need is i created a executable jar file with certain classes.
and i'm supposed to send it to my client.
but if the client needs he can extract the class files from the jar and with the
help of some decompilers he can convert class file to .java source code and read the whole
stuff.
how can i protect my jar file from these.
is there any security mechanism for that
pls help me.
Regards,
Ranjith.M

In order to protect my jar file I tried the jar signer technology but it only protects the jar from modification so I need to know how to protect jar file from decoding of the contents inside.

Howto resolve the path to the class file

hi @ all,
i'm currently developing a package for ldap operations. now i want to write down all the real basic configuration for that package into a xml file which i want to save in the folder where the compiled class files are stored. my problem is that i do not know how i can resolve the absolute path to that xml file later. i mean, how can i load this file if the package is, e.g. exported as an jar file and i do not know where this jar file will be stored by the users of my package.
can anyone help me with that please?
thx in advance
dialsc

k, cool...
looks like it goes into the right direction.
with this statement i get the path where the jar is stored, right.
in my current situation this is the path to the src directory which i configured my eclipse ide to store the class files under.
let's say this path is d:\tmp\src
my package is tdl.domain.utils.ldap
so in fact at the moment my class files are stored under d:\tmp\src\tdl\domain\utils\ldap and the xml file too.
first:
that statement returns /D:/tmp/src
as you can see it uses unix path separators. do i have to replace them with the machine specific pathSeparatorChar?
second:
can is simply add the path tdl\domain\utils\ldap to that one (using the according machine specific pathSeparatorChar) and will this also work when i build a jar file of my package?
sorry for all that questions but i realy need this...
thx
dialsc

Recent changes to the class file format?

I have the JVM Spec, 2nd ed., on my desk. I'm trying to find out about changes to the class file format since its publication, i.e. what are the differences between class file versions 46.0, 47.0 and 48.0?
So far, searching the JDC and the web hasn't helped. Does a document describing the changes exist?

I have not found a list of changes, but the 2nd edition is at
http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html
Clarifications and Amendments to The Java Language Specification at http://java.sun.com/docs/books/jls/clarify.html has a section
"Compilation of Symbolic References"
that is useful.
http://forum.java.sun.com/thread.jsp?forum=31&thread=27569
says:
javac v1.4 emits by default Java 1.2 compatible .class files while
all javac implementations since between 1.1.0 and 1.3.1 emit byte
default Java 1.1 .class files.
Check to see what effect using the -target option in javac to get
the two versions to produce Java 1.1, 1.2, or 1.3 .class files.
discusses using javac -target to generate
-Christopher

Compiling on a dual core machine and running the class files on linux.

does compiling on a dual core machine and running the class files on linux have any effect?

well, the problem that i felt was that when i runmy
class files on my machine(windows xp, dual core),
Thread.sleep(60000) sleeps for 1 minute. but wheni
run it on a linux machine, Thread.sleep(60000)sleeps
for 2 minutes. my application has a lot ofthreads.
I can't be 100% sure, but I'm pretty sure that
sleep(60000) doesn't sleep for 2 minutes on the other
machine.I, wholeheartedly, agree.
Due to timing issues it may seem to sleep a few milliseconds more, but not double.
Of course, if there is a "real-time" (or even simply higher than the Java app) priority program running that is using a lot of the CPU it may seem like it sleeps a lot longer than 60000, but that is a different issue.

How to find the arguments of a static method from the class file

Hi,all !
How to find the arguments of a static method from the class file? for example, when we meet a bytecode "invokestatic", how can I know the arguments of this static method?

Hi,all !
How to find the arguments of a static method from the
class file? for example, when we meet a bytecode
"invokestatic", how can I know the arguments of this
static method?You mean
1. The values?
2. Argument names?
3. Argument signatures.
I would suppose for the last that the easiest way would be to parse the signature string.
The first is not possible - not from the class file.
The second is only in the debug information stored in the optional part of the class file. And figuring out the format for that is going to be a problem.

Junk values when decompiling the class file

Hi All,
When i decompiling the class file , i am getting junk values i.e <file>.class$java.lang.string and _mtclass$("java.lang.string").
I am using JAD for decompilation .
Can any body help.. how remove the junk data

ya and better part being that its an issue with the tool used for decompilation. Nothing specific to OAF here. Any class file will behave in the same way to this tool.
--Shiv

Advice on encrypting the class files so that it cannot be reverse engineer

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