I asked backdoor author - why he uses UPX 1.01 not 1.24 (1.24 compress at higher ratio)? He wrote: "i dont like UPX 1.24 it corrupts things".
I made CRC32 for one exe. Then packed with --best setting using UPX 1.24 and then unapacked. CRC32 test failed.

What do You think?

I removed "HA Tools" from the topic of this thread (as well as moved to the off-topic section). I don't really understand why it was there since UPX has nothing specifically to do with HA, and the HA Tools of past (which have been abandoned) were something completely different.

Of course the CRC failedm the filesizes are different, It would be like CRCing a file, then compress it to Zip and CRC the zip file.

UPX is lossless. Think of it like a self-extracting Zip file.

BTW. What does this has to do with audio??

He said he CRC'd the file, packed it using UPX 1.24, unpacked it, and then CRC'd the file again and it failed. Not so lossless after all.

I don't think UPX guarantees anywhere that it is lossless.

UPX is used for audio encoders, decoders, players etc. compressing.

So, which part of code is lost? Maybe UPX is loseless, but it changes file...

It may be something as simple as discarding un needed headers, debug info, or varrious other non essential data. The key here is if the functionality or reliability is altered? Any comments?

UPX is used for a lot more than audio players and encoders.

UPX isn't lossless though. By default it will strip relocation segments from .exes (although Delphi is the only compiler I've run across that actually adds them), and it can be configured to strip overlays from .exes as well. It does "other stuff" too, although I'm not sure exactly what.

The parts that are stripped out generally aren't needed (otherwise you'd have a broken program). At a guess, I'd say that the majority of the exes that get b0rked are the ones doing some serious black magic with the format. For example, anti-piracy components or self-modifying executables. (Not that either are necessarily bending the PE format in directions it didn't know it could go, but both areas are much more likely to do this than, say, a VB developer making a pretty GUI.)

Hmmm..

I got that this time!

i got the latest version of ASPack.. i find it better than UPX.. harder to crack for the n00bs

but hey, nothing is uncrackable.

Also, most of the unpacker for aspack if found couldnt replicate the file correctly...

Better use ASProtect, even harder to crack.

I like UPX, because it also packs DOS and linux files