Reverse Engineering Stack Exchange
Reverse Engineering Stack Exchange

Questions tagged [decompress]

Process of decoding a compressed file to get back to the original one. Some compression software may also include encryption or obfuscation in order to protect their format/algorithm.

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What compression algorithm is this?

I've reversed the following decompression algorithm from a game. It appears to be some variant of LZ77, however none of the descriptions of variants seem quite close enough what I've got. Is this a specific flavor of LZ77, and if not, how would I go…
kirby
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Unknown decompression algorithm

I work on the reverse engineering of the ChessBase archive (.cbv). I found the general structure of the file and can already decompress some files. You can see my current work here. However, some .cbv files that are bigger seems to use a second…
antoyo
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How is PTX compressed in a fatbinary?

It is not clear how PTX is compressed in a fatbinary. I'm doing some research and by looking at the binary it seems a sort of LZ77 (or LZSS?). I've prepared some tests: Small PTX. A simple vec_add (poorly implemented): Input,Output and CUDA…
fusiled
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Unknown compression (Decompression reversed)

I've reversed a decompression routine, but have to figure out the compression. Because the executable only decrypts and therefor has no compression routine and I'm not comfortable with compressions it's really hard for me. Here the code I've written…
user9926
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Serialized body (Protobuf?)

There is an application on iOS that collects data and encrypts it in the future. Data is already serialized at entry to the encryption function, they look like this(I tried to decode, restore the scheme, but nothing comes out, I hope for the help of…
solocef
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Compression format used for various data (images, text, etc.) in a 1997 video game

I've been trying to reverse engineer the format of data files from the 1997 video game Helicops. I have experience reverse engineering binary files from games of this period but limited exposure to compression schemes. I've been able to figure out…
Reign of Error
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What kind of deflate compression is this?

I must be missing something obvious here. I cannot make sense of the following deflate stream. Steps: % wget https://github.com/lrq3000/mri_protocol/raw/master/SiemensVidaProtocol/Coma%20Science%20Group.exar1 % sqlite3 Coma\ Science\ Group.exar1…
tibar
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Find decompression algorithm based on known compression implementation

I have been trying to figure out how this compression algorithm works, so I can write a decompression tool for it. The compressed data consists of the following layout: 0x00 → 0x03 : uncompressed data size (4 bytes, e.g. 0x80) 0x04 → 0x83 :…
David Refoua
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How to interpret the final 0x03 0x00 in this minimal gzip sample?

I'm reading gzip format specification, trying to understand byte-to-byte the following minimal example (generated using echo -n | gzip > /tmp/a.gz): 00000000 1f 8b 08 00 70 3c b4 5d 00 03 03 00 00 00 00 00 |....p<.]........| 00000010 00 00 00 00…
d33tah
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What compression type has been used here?

I am still working on the binary image from the last question, and have already found out that my "corrupted" data is actually just compressed. But now I have another issue because I don't know what compression type was used. What I already…
Lukas S.
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Trying to figure what kind of compression was used

I got the following raw data, which are the first 35 bytes of a compressed png image: 00 89 50 4e 47 0d 0a 1a 0a 00 00 00 00 0d 49 48 44 52 08 00 00 02 58 00 83 5a 08 06 80 00 83 64 31 28 fe I also happened to have the 33 bytes the above 35 bytes…
user20145
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Extracting .ovl and .aux files?

I recently got a copy of a space game and id like to be able to extract the audio/models from the game. I've attached an example .ovl file and a .aux file below. I have no knowledge on reverse engineering file formats. So I'm sorry if I'm not the…
user3851593
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How to decompress this file

I'm trying to figure out how this old game is (de)compressing files, but I don't have much knowledge about file compression. I tried running the game from a debug tool to see if I could spot something in the assembly, but that's way over my…
Oli
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Recreated LZMA differs from the original after 332 bytes

Recently I decompressed an LZMA file from a VxWorks filesystem which was recognized and decompressed by the LZMA SDK with parameters lc = lp = 0, pb = 2 and dictionary size 8MB. When I recompressed it (without modification, using the same tools and…
Awais Chishti
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Decompressing a .replay file

Fortnite has a feature that records your gameplay and saves it as a .replay file, now I don't believe these files are encrypted, only compressed. I wasn't able to find a way online to decompress such files and I'd like to know how, and if there's a…
rhyminister
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