Comments on: A better way to publically demonstrate ground-breaking compression algorithms without risking reverse-engineering.

By: Goldy

Goldy — Thu, 14 Jul 2005 11:31:05 +0000

Please keep this post.
I did the original post on comp.compression.

I never mentioned anything about reverse engineering the decompressor, as that was not the question being asked.

Yes, you could very easly reverse engineer a decompressor, but would you still want to if you got the compressor for free? ;)

By: Sachin Garg

Sachin Garg — Thu, 30 Jun 2005 15:59:45 +0000

Hmmm… I agree that in many cases algorithm can be reverse engineered from the decompressor, at least to a large extent.

As you might have noticed from the comp.compression thread, the method was posted by the inventor, so it was assumed that the inventor was willing to give away the decompressor.

Thus, I never gave too much thought on inventor’s perspective. But as a perspective evaluator, I was satisfied by the method.

I have made some changes to the text in news item, please point out any other shortcomings in it.

If you feel that I should remove this news item, I will.

By: Alfredo De la Cruz

Alfredo De la Cruz — Thu, 30 Jun 2005 07:55:13 +0000

I am sorry to deeply disagree also with the statement regarding that this method does not allow reversing engineering. In lossless compression, once that you have managed to know the decompression algorithm, have an input data (the compressed file) and and output data (the original file) it is very hard to imagine a compression algorithm that could not be reconstructed, at least to an engineering level where you can get the main ideas behind and generate your own compressor.
Lossless compression, at least for the efficient algorithms, can mostly be seen as a highly sophisticated state machine, where you jump from state to state according to the input data, generating at the same time the shortest output possible. Reversely, the decompression algorithm have to replicate the same state machine, but now travelling in the other way around.

By: Jim Leonard

Jim Leonard — Wed, 29 Jun 2005 18:40:11 +0000

“As the compressor never leaves the hands of original inventor, he can relax that it cant be reverse engineered.” I disagree — some methods, like LZ78, *can* be deduced by looking at the decompressor, since the decompressor build the dictionary as it goes.