Homework

Z

zero

After an idea pitched by someone here (I don't remember who, sorry),
I've created this template for homework help. Changing the class or
method names breaks the code, and so does adding or removing lines above
the catch block, making it hard to pass this off as the student's own
work. And if they do succeed in changing it enough, I think they
deserve to pass ;-) Of course the code specific to the assignment
should have some pitfalls too, so they can't just copy and paste into
their own class.

Yes, I have too much time on my hands.



import java.lang.reflect.Method;
import java.math.BigInteger;

public class DoYourHomeworkYourself
{
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u006E\u0061\u006D\u0065\u003D\u0020
\u0022\u0044\u006F\u0059\u0022\u002B
\u0022\u006F\u0075\u0072\u0048\u0022
\u002B\u0022\u006F\u006D\u0022\u002B
\u0022\u0065\u0077\u006F\u0072\u0022
\u002B\u0022\u006B\u0059\u006F\u0022
\u002B\u0022\u0075\u0072\u0073\u0022
\u002B\u0022\u0065\u006C\u0066\u0022
\u003B\u000A\u000C\u0009\u0020\u0020
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u006D\u006E\u0061\u006D\u0065\u003D
\u0022\u0072\u0075\u006E\u0048\u0022
\u002B\u0022\u006F\u006D\u0065\u0022
\u002B\u0022\u0077\u006F\u0072\u0022
\u002B\u0022\u006B\u0022\u003B\u000C
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u0070\u006E\u0061\u006D\u0065\u003D
\u0022\u0072\u0075\u006E\u0022\u003B
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u0072\u006E\u0061\u006D\u0065\u003D
\u0022\u007F\u0071\u0052\u0022\u003B
static String num = "\u0034\u0039";

public void run()
{
System.out.println("thanks to comp.lang.java.programmer");
}

public static void main(String args[]) throws Exception
{
try
{
Class aClass = Class.forName(name);
Object anObject = aClass.newInstance();
Method method1 = aClass.getMethod(mname, (Class[])null);
method1.invoke(anObject, (Object[])null);
Method method2 = aClass.getMethod(pname, (Class[])null);
method2.invoke(anObject, (Object[])null);
Method method3 = aClass.getMethod(rname, (Class[])null);
method3.invoke(anObject, (Object[])null);
}
catch(Exception e)
{
if(e.getStackTrace()[1].getLineNumber()
!= new BigInteger(num).intValue())
throw new Error("Don't tamper with my code");
}
}

public void runHomework()
{
System.out.println("homework specific code goes here");
}
}
 
T

tom fredriksen

zero said:
After an idea pitched by someone here (I don't remember who, sorry),
Click to expand...

Do you have a description of the idea,

I've created this template for homework help...
Click to expand...
Yes, I have too much time on my hands.
Click to expand...

The fact that you coded this is fabulously insane:) thank you, it made
my day :))

/tom
import java.lang.reflect.Method;
import java.math.BigInteger;

public class DoYourHomeworkYourself
{
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u006E\u0061\u006D\u0065\u003D\u0020
\u0022\u0044\u006F\u0059\u0022\u002B
\u0022\u006F\u0075\u0072\u0048\u0022
\u002B\u0022\u006F\u006D\u0022\u002B
\u0022\u0065\u0077\u006F\u0072\u0022
\u002B\u0022\u006B\u0059\u006F\u0022
\u002B\u0022\u0075\u0072\u0073\u0022
\u002B\u0022\u0065\u006C\u0066\u0022
\u003B\u000A\u000C\u0009\u0020\u0020
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u006D\u006E\u0061\u006D\u0065\u003D
\u0022\u0072\u0075\u006E\u0048\u0022
\u002B\u0022\u006F\u006D\u0065\u0022
\u002B\u0022\u0077\u006F\u0072\u0022
\u002B\u0022\u006B\u0022\u003B\u000C
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u0070\u006E\u0061\u006D\u0065\u003D
\u0022\u0072\u0075\u006E\u0022\u003B
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u0072\u006E\u0061\u006D\u0065\u003D
\u0022\u007F\u0071\u0052\u0022\u003B
static String num = "\u0034\u0039";

public void run()
{
System.out.println("thanks to comp.lang.java.programmer");
}

public static void main(String args[]) throws Exception
{
try
{
Class aClass = Class.forName(name);
Object anObject = aClass.newInstance();
Method method1 = aClass.getMethod(mname, (Class[])null);
method1.invoke(anObject, (Object[])null);
Method method2 = aClass.getMethod(pname, (Class[])null);
method2.invoke(anObject, (Object[])null);
Method method3 = aClass.getMethod(rname, (Class[])null);
method3.invoke(anObject, (Object[])null);
}
catch(Exception e)
{
if(e.getStackTrace()[1].getLineNumber()
!= new BigInteger(num).intValue())
throw new Error("Don't tamper with my code");
}
}

public void runHomework()
{
System.out.println("homework specific code goes here");
}
}
Click to expand...
 
A

Alun Harford

X-No-Archive:Yes

zero said:
After an idea pitched by someone here (I don't remember who, sorry),
I've created this template for homework help. Changing the class or
method names breaks the code, and so does adding or removing lines above
the catch block, making it hard to pass this off as the student's own
work. And if they do succeed in changing it enough, I think they
deserve to pass ;-) Of course the code specific to the assignment
should have some pitfalls too, so they can't just copy and paste into
their own class.

Yes, I have too much time on my hands.
Click to expand...

No, sorry but it won't work yet - too easy to get around, even if you don't
know the "secret".
Still, with a little work, it could be made harder. More <secret method I'm
not going to divulge> is required, particularly around the vulnerable try {}
catch {} block. There is also much fun to be had with
java.lang.ClassLoader.defineClass(...)

I've set X-No-Archive:Yes on this message. Any other "spoiler" replies
should do the same.

Alun Harford

import java.lang.reflect.Method;
import java.math.BigInteger;

public class Tampered
{
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u006E\u0061\u006D\u0065\u003D\u0020
\u0022\u0044\u006F\u0059\u0022\u002B
\u0022\u006F\u0075\u0072\u0048\u0022
\u002B\u0022\u006F\u006D\u0022\u002B
\u0022\u0065\u0077\u006F\u0072\u0022
\u002B\u0022\u006B\u0059\u006F\u0022
\u002B\u0022\u0075\u0072\u0073\u0022
\u002B\u0022\u0065\u006C\u0066\u0022
\u003B\u000A\u000C\u0009\u0020\u0020
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u006D\u006E\u0061\u006D\u0065\u003D
\u0022\u0072\u0075\u006E\u0048\u0022
\u002B\u0022\u006F\u006D\u0065\u0022
\u002B\u0022\u0077\u006F\u0072\u0022
\u002B\u0022\u006B\u0022\u003B\u000C
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u0070\u006E\u0061\u006D\u0065\u003D
\u0022\u0072\u0075\u006E\u0022\u003B
\u0073\u0074\u0061\u0074\u0069\u0063
\u0053\u0074\u0072\u0069\u006E\u0067
\u0072\u006E\u0061\u006D\u0065\u003D
\u0022\u007F\u0071\u0052\u0022\u003B
static String num = "\u0034\u0039";

public void run()
{
System.out.println("thanks to comp.lang.java.programmer");
}

public static void main(String args[]) throws Exception
{
try
{
//tamper, tamper, tamper
//I can comment out the code below and just invoke runHomework();
Class aClass = Class.forName(name);
Object anObject = aClass.newInstance();
Method method1 = aClass.getMethod(mname, (Class[])null);
method1.invoke(anObject, (Object[])null);
Method method2 = aClass.getMethod(pname, (Class[])null);
method2.invoke(anObject, (Object[])null);
Method method3 = aClass.getMethod(rname, (Class[])null);
method3.invoke(anObject, (Object[])null);
}
catch(Exception e)
{
if(e.getStackTrace()[1].getLineNumber()
!= new BigInteger(num).intValue())
//throw new Error("Don't tamper with my code");
//Above line commented out so can tamper
; //Just needs a semi-colon
}
}

public void runHomework()
{
System.out.println("homework specific code goes here");
}
}
 
Z

zero

Do you have a description of the idea,
Click to expand...

It was simply to have a class with the name I gave my class, and
preventing it from being changed.
The fact that you coded this is fabulously insane:) thank you, it made
my day :))
Click to expand...

glad you liked it :) Feel free to post any ideas you have for
improvement.
 
Z

zero

public static void main(String args[]) throws Exception
{
try
{
//tamper, tamper, tamper
//I can comment out the code below and just invoke
runHomework(); Class aClass = Class.forName(name);
Object anObject = aClass.newInstance();
Method method1 = aClass.getMethod(mname, (Class[])null);
method1.invoke(anObject, (Object[])null);
Method method2 = aClass.getMethod(pname, (Class[])null);
method2.invoke(anObject, (Object[])null);
Method method3 = aClass.getMethod(rname, (Class[])null);
method3.invoke(anObject, (Object[])null);
}
catch(Exception e)
{
if(e.getStackTrace()[1].getLineNumber()
!= new BigInteger(num).intValue())
//throw new Error("Don't tamper with my code");
//Above line commented out so can tamper
; //Just needs a semi-colon
}
}
Click to expand...

I moved the reflection into the try block right before posting - before
that, any exceptions were just thrown by main, and the linenumber check
was done with a throws clause. I thought the trhows clause was too
obvious. I shouldn't have moved all the reflection code into the try
block though, that does indeed make it easy to circumvent.

When I have the courage to work on it again, I'll try to come up with a
better scheme :)
 
S

Stefan Ram

zero said:
When I have the courage to work on it again, I'll try to come up with a
better scheme :)
Click to expand...

People sometimes tell me that the way, I format my source code
renders it "unreadable". For example, just several minutes
ago, someone on de.comp.lang.java asked how to enumerate all
getters of a class using an array and I replied (suppressing
the temptation to use reflection):

class TestObject
{ private final java.lang.String nameGiven = "Hannah";
private final java.lang.String nameSur = "Anderson";
public java.lang.String getNameGiven(){ return this.nameGiven; }
public java.lang.String getNameSur(){ return this.nameSur; }
@SuppressWarnings("unchecked")
private java.util.concurrent.Callable<java.lang.String>[] getters =
( java.util.concurrent.Callable<java.lang.String>[] )
new java.util.concurrent.Callable[]
{ new java.util.concurrent.Callable<java.lang.String>()
{ public java.lang.String call(){ return TestObject.this.getNameGiven(); }},
new java.util.concurrent.Callable<java.lang.String>()
{ public java.lang.String call(){ return TestObject.this.getNameSur(); }}};
public java.util.concurrent.Callable<java.lang.String>[]
getGetters(){ return getters; }}

public class Main
{ public static void main( final java.lang.String[] args )
throws java.lang.Exception
{ final TestObject testObject = new TestObject();
for( java.util.concurrent.Callable<java.lang.String> getter:
testObject.getGetters() )
{ java.lang.System.out.println( getter.call()) ; }}}

Then another experienced posters said, he was not able to read
what I had written, so he will not comment but ignore it.

So maybe my style of formatting is an answer to your problem?

In a sense, I give the one asking a question a hint, but he
still will have to invest work decyphering it (like
reformatting it in his preferred way).
 
O

Oliver Wong

Stefan Ram said:
zero said:
When I have the courage to work on it again, I'll try to come up with a
better scheme :)
Click to expand...

People sometimes tell me that the way, I format my source code
renders it "unreadable". For example, just several minutes
ago, someone on de.comp.lang.java asked how to enumerate all
getters of a class using an array and I replied (suppressing
the temptation to use reflection):

class TestObject
{ private final java.lang.String nameGiven = "Hannah";
private final java.lang.String nameSur = "Anderson";
public java.lang.String getNameGiven(){ return this.nameGiven; }
public java.lang.String getNameSur(){ return this.nameSur; }
@SuppressWarnings("unchecked")
private java.util.concurrent.Callable<java.lang.String>[] getters =
( java.util.concurrent.Callable<java.lang.String>[] )
new java.util.concurrent.Callable[]
{ new java.util.concurrent.Callable<java.lang.String>()
{ public java.lang.String call(){ return
TestObject.this.getNameGiven(); }},
new java.util.concurrent.Callable<java.lang.String>()
{ public java.lang.String call(){ return
TestObject.this.getNameSur(); }}};
public java.util.concurrent.Callable<java.lang.String>[]
getGetters(){ return getters; }}

public class Main
{ public static void main( final java.lang.String[] args )
throws java.lang.Exception
{ final TestObject testObject = new TestObject();
for( java.util.concurrent.Callable<java.lang.String> getter:
testObject.getGetters() )
{ java.lang.System.out.println( getter.call()) ; }}}

Then another experienced posters said, he was not able to read
what I had written, so he will not comment but ignore it.

So maybe my style of formatting is an answer to your problem?

In a sense, I give the one asking a question a hint, but he
still will have to invest work decyphering it (like
reformatting it in his preferred way).
Click to expand...


Alternatively, he might load it up in Eclipse and press CTRL-F to have
it automatically formatted.

I think the ultimate goal here is to find a way to "encrypt" Java source
code such that the encrypted version produces identical output to the
original program, that the encrypted version will fail whenever any portion
of it is modified, and translating from the encrypted version into the
unencrypted version is NP-Complete (or possibly not Turing Computable).

- Oliver
 
S

Stefan Ram

Oliver Wong said:
private java.util.concurrent.Callable<java.lang.String>[] getters =
( java.util.concurrent.Callable<java.lang.String>[] )
new java.util.concurrent.Callable[]
{
Click to expand...
Alternatively, he might load it up in Eclipse and press CTRL-F to have
it automatically formatted.
Click to expand...

This will combine the above 3 lines (plus one character) into
a single long line with about 161 characters in Eclipse 3.2:

private java.util.concurrent.Callable<java.lang.String>[] getters = (java.util.concurrent.Callable<java.lang.String>[]) new java.util.concurrent.Callable[] {

Is this now considered to be more readable?

Or compare my line break:

for( java.util.concurrent.Callable<java.lang.String> getter:
testObject.getGetters() )

with where Eclipse broke these two lines:

for (java.util.concurrent.Callable<java.lang.String> getter : testObject
.getGetters())

Is this a better break point?

Moreover, it was not that simple:

- When I started Eclipse, it complained that it could
not find "jdk1.5.0" and it took me some time to find
out how to tell Eclipse that I have removed 1.5.0 and
that it should use 1.6.0

- Then, when it finally started, Windows froze and I
had to reboot and to run Scandisk

This took so much time, that it would have been much faster
to reformat by hand.

Moreover, not everybody asking a question would not
how to operate Eclipse or a similar formatter.
 
O

Oliver Wong

Stefan Ram said:
Oliver Wong said:
private java.util.concurrent.Callable<java.lang.String>[] getters =
( java.util.concurrent.Callable<java.lang.String>[] )
new java.util.concurrent.Callable[]
{
Click to expand...
Alternatively, he might load it up in Eclipse and press CTRL-F to have
it automatically formatted.
Click to expand...

This will combine the above 3 lines (plus one character) into
a single long line with about 161 characters in Eclipse 3.2:

private java.util.concurrent.Callable<java.lang.String>[] getters =
(java.util.concurrent.Callable<java.lang.String>[]) new
java.util.concurrent.Callable[] {

Is this now considered to be more readable?

Or compare my line break:

for( java.util.concurrent.Callable<java.lang.String> getter:
testObject.getGetters() )

with where Eclipse broke these two lines:

for (java.util.concurrent.Callable<java.lang.String> getter : testObject
.getGetters())

Is this a better break point?
Click to expand...

I don't know about these specific examples, but whenever someone posts
some Java code on these newsgroups formatted in a way I don't approve of, I
just copy and paste the code into Eclipse and use its formatting facility.
That, combined with its syntax highlight, mouse over info and code
navigation, usually allows me to understand what the code is doing pretty
quickly. I sometimes also use the refactoring facilities to rename the
variables and methods to something more meaningful to me.
Moreover, it was not that simple:

- When I started Eclipse, it complained that it could
not find "jdk1.5.0" and it took me some time to find
out how to tell Eclipse that I have removed 1.5.0 and
that it should use 1.6.0

- Then, when it finally started, Windows froze and I
had to reboot and to run Scandisk

This took so much time, that it would have been much faster
to reformat by hand.

Moreover, not everybody asking a question would not
how to operate Eclipse or a similar formatter.
Click to expand...

I was thinking of the "worst case" of someone who is infinitely smart,
but wants to do the minimal amount of work to get a homework assignment
done. It's basically a form of the "adversarial" argument. We're trying to
come up with ways of formatting Java Code so that they could not be used in
homework without making it obvious to the teacher that the code was
plagiarised. But every technique we've come up with so far could be machine
translated into a form where the plagiarism isn't so obvious.

- Oliver
 

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