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Old 16 November 2011, 22:36   #1
Lonewolf10
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>> Decryption Challenge <<

The attached file is an image from my upcoming Amiga demo, and was created by me in Wings 3D (pc software) and rendered using POV-Ray (in 8-bit mode, and again it's PC software). I then used MS Paint to reduce it down to 16 colours. It has been encrypted and it's up to you to try to decrypt it!


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Old 16 November 2011, 22:50   #2
prowler
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This is a far more difficult challenge than cracking encrypted graphics on a demo if you do not include the code to display the image.

Last edited by prowler; 16 November 2011 at 23:00.
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Old 17 November 2011, 08:59   #3
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Lonewolf10: I'm kind of with prowler on this one. This decryption challenge is not the same as the decryption challenge required to decrypt the data of your demo.

When your demo is released, it won't just be a lump of encrypted data - lurking within it will be the decryption code that must surely be there so that your own demo can decrypt the encrypted graphics data ready for display.

So, even if no-one here can decrypt the encrypted data you've posted, they still might get at your data when it comes bundled with the necessary decryption code in your demo.

No one would need to try pick the lock in that instance - they'd already have the key...
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Old 17 November 2011, 09:19   #4
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What prowler and pmc said! Just attaching the encrypted data is kinda useless, even if no one can decrypt it (I'm not even gonna waste any time to download it!) it doesn't mean that your encryption is any good! Post a binary and then we'll see... After all, you want to use the encrypted data in a demo so provide the binary!
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Old 17 November 2011, 13:28   #5
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While it's generally true that trying to decrypt data without the algorithm (or a cryptographically secure stream cypher without the key) is quite useless, it never hurts to look at the data anyway. Also, it helps knowing what the data is supposed to be.

In this case, a small, repeating and simple piece of data has likely been used. Analyzing the differences between these blocks may provide you with the data needed to decrypt the image.

Last edited by Thorham; 17 November 2011 at 22:00.
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Old 17 November 2011, 18:55   #6
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I consider it wasted time trying to decrypt an image that'll be used in a demo. Impossible is nothing and I too have decrypted data without knowing the encryption algo (and I didn't even know what data I had to expect after decrypting either!).

Thing is, there is absolutely no need to waste any time trying to decrypt the attached data since it'll end up in a demo sooner or later and can then be decrypted easily. It's not that it is top secret data or anything, then I would see a reason trying to decrypt it. Just my 2 cents.
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Old 17 November 2011, 22:19   #7
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Quote:
Originally Posted by Thorham View Post
Also, it helps knowing what the data is supposed to be.
It's raw image data that has been encrypted. I thought about attaching the unencrypted image too, perhaps that would be better?


Quote:
Originally Posted by Thorham View Post
In this case, a small, repeating and simple piece of data has likely been used. Analyzing the differences between these blocks may provide you with the data needed to decrypt the image.
Someone's on the right track...

Quote:
Originally Posted by StingRay View Post
Just attaching the encrypted data is kinda useless, even if no one can decrypt it (I'm not even gonna waste any time to download it!) it doesn't mean that your encryption is any good! Post a binary and then we'll see... After all, you want to use the encrypted data in a demo so provide the binary!
I'll post a binary sometime this weekend (most likely on Saturday). The demo (if all goes as planned) will be out in December anyway...


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Lonewolf10
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Old 18 November 2011, 08:28   #8
musashi5150
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Quote:
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I consider it wasted time trying to decrypt an image that'll be used in a demo
Let's just take a screenshot with a monitor when it is shown on screen
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Old 18 November 2011, 08:47   #9
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Quote:
Originally Posted by Lonewolf10 View Post
It's raw image data that has been encrypted. I thought about attaching the unencrypted image too, perhaps that would be better?
How about posting the raw image?

First to post a routine that decrypts the data back to raw wins?

Red
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Old 18 November 2011, 12:04   #10
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Quote:
Originally Posted by StingRay View Post
I consider it wasted time trying to decrypt an image that'll be used in a demo. Impossible is nothing and I too have decrypted data without knowing the encryption algo (and I didn't even know what data I had to expect after decrypting either!).

Thing is, there is absolutely no need to waste any time trying to decrypt the attached data since it'll end up in a demo sooner or later and can then be decrypted easily. It's not that it is top secret data or anything, then I would see a reason trying to decrypt it. Just my 2 cents.
Right.
Here is better data for challenge. This is ROM file from rare arcade game MoonQuake.
Crypted data starts from $3C3E offset. These data are perhaps decrypted by hardware to $300000 address, I can't found decrypt routine inside ROM. If someone is able to decode this ROM, then perhaps WHDload install can be created for this game.
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Old 19 November 2011, 02:10   #11
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Originally Posted by RedskullDC View Post
How about posting the raw image?

First to post a routine that decrypts the data back to raw wins?
For those that are still interested in my challenge, I have attached the unencrypted raw image data. I will hold off posting the binary for now.


Quote:
Originally Posted by Don_Adan View Post
Here is better data for challenge. This is ROM file from rare arcade game MoonQuake.
Crypted data starts from $3C3E offset. These data are perhaps decrypted by hardware to $300000 address, I can't found decrypt routine inside ROM. If someone is able to decode this ROM, then perhaps WHDload install can be created for this game.
I have never heard of that game. Will take a look at that myself when I find the time.


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Old 19 November 2011, 04:35   #12
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Originally Posted by Lonewolf10 View Post
For those that are still interested in my challenge, I have attached the unencrypted raw image data. I will hold off posting the binary for now.

Regards,
Lonewolf10
Ok...

Repeating sequence of bytes, $2C in length:

43444937 434E493E 435F4916 43784957 43E2483A 42F74B8A 472C4E17 48D65B86 5D0F79CE 0C00C977 8CCA4932

or 11 long words.

Each long word from the Encrypted image data is XORed with the corresponding long word from the list above then rotated by 16 ( or 68K "SWAP" ).

Example:

Encrypted data offset $AA8: $BC04493C
XOR with corresponding long word: $43444937
= $FF40000B
after swap: $000BFF40

Data in RAW Image file at $AA8: $000BFF40

That was fun

Cheers,
Red
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Old 19 November 2011, 11:06   #13
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Quote:
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Right.
Here is better data for challenge. This is ROM file from rare arcade game MoonQuake.
Crypted data starts from $3C3E offset. These data are perhaps decrypted by hardware to $300000 address, I can't found decrypt routine inside ROM. If someone is able to decode this ROM, then perhaps WHDload install can be created for this game.
Hi,

There is something interesting ( or mean nothing ): block of data from $3c3e - $20000 is equal to the $4000c - $5c3ce.

Regards
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Old 22 November 2011, 19:27   #14
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If I were to upload an encrypted text file to be cracked, what else would you want me to upload? The source code, executable, detailed explanation, all the above, or what? I have an encryption program and it would be interesting to see how good or bad it really is.
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Old 22 November 2011, 21:34   #15
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Quote:
Originally Posted by Ed Cruse
I have an encryption program and it would be interesting to see how good or bad it really is.
I think the answer to this question varies depending on how the encrypted data will be used.

If you're using it to encrypt data files purely to stop people getting at the data and those files are stored without the encryption key contained in them (more secure) then that's completely different to a demo type encryption where, by necessity, the code to decrypt the data will be included (less secure).

So, what you post in order to allow people to test how secure your encryption algorithm is would all depend on the context in my opinion.
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Old 23 November 2011, 16:26   #16
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I think the answer to this question varies depending on how the encrypted data will be used.

If you're using it to encrypt data files purely to stop people getting at the data and those files are stored without the encryption key contained in them (more secure) then that's completely different to a demo type encryption where, by necessity, the code to decrypt the data will be included (less secure).

So, what you post in order to allow people to test how secure your encryption algorithm is would all depend on the context in my opinion.
OK, that makes sense.

Would anybody be interested in cracking a random key encryption where you have an encrypted text file, the executable for encrypting and de-encrypting, and a detailed description of the algorithm? I realize that this type of encryption is mostly uncrackable unless there's a flaw that can be exploited. This is what I would like to find out. The algorithm could be crap and very easy to crack.

Any takers?
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Old 23 November 2011, 17:26   #17
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Any takers?
If you're interested in finding out whether an encryption algorithm you've developed is secure or not, I suggest you discuss the mathematics with cryptographers. While programmers often have a general idea of how encryption works, most don't have the special competance required to judge the security of a non-standard algorithm.

Encrypted data in games or demos is an entirely different matter, because the encryption key is known. It's a matter of understanding (obfuscated) code, not breaking encryption.
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Old 24 November 2011, 11:50   #18
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Quote:
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Would anybody be interested in cracking a random key encryption where you have an encrypted text file, the executable for encrypting and de-encrypting, and a detailed description of the algorithm? I realize that this type of encryption is mostly uncrackable unless there's a flaw that can be exploited. This is what I would like to find out. The algorithm could be crap and very easy to crack.

Any takers?
Uncrackable? BAH!

Sure, post some stuff for us to have a look at.

Description of the algortihm will probably make it too easy though.
Just the EXE and the encrypted file should do

Red
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Old 24 November 2011, 15:38   #19
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Some links about MoonQuake:
http://www.classicarcadegaming.com/e...es/mda/107.htm
http://aarongiles.com/?p=174
http://www.classicarcadegaming.com/e...es/mda/171.htm
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Old 24 November 2011, 20:18   #20
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Here's my executable and encrypted text file.

Encrypt.exe is a CLI program, if you type "encrypt ?" it will print the args template.

Examples:

To encode - encrypt.exe 1234 filename encode

To decode - encrypt.exe 1234 filename

If the password is incorrect you'll get an error message saying so. If you crack it, attach it and let me see how good you cracked it by comparing against the original. You can simply encrypt your own files also, that way you at least know what's in it and maybe figure it out. Good luck.
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