A compression/decompresson script (with optional GUI) that allows user to compress/decompress Nintendo Switch ROMs loselessly, thanks to zstd compression algorithm. The compressed file can be installed directly with supported NSW Homebrew Title Installers.
There are several ways to use the script. You can find details on installation for all below.
You need to have a hactool compatible keys file in a suitable directory to use the script.
The keys file must be located as prod.keys file in %USERPROFILE%/.switch/(Windows)/$HOME/.switch/(UNIX) or keys.txt in the working directory.
It can be dumped with Lockpick_RCM.
You can also use the Windows binaries. They do not require any external libraries to be installed and can be run without installing anything. You can find the binaries in the release page.
Methods listed below requires you to have Python 3.6+ and the pip package manager installed.
Python 3.8 and later requires Microsoft C++ Build Tools if you are want to use the GUI.
Simplest way to install would be using the following command in a terminal or a command prompt.
pip3 install --upgrade nsz
If you are interested in installing the GUI for the script, you can do so by running the following command.
pip3 install --upgrade nszgui
The script can also be run by cloning the repo locally. You need to install the pre-requisite modules by running the following command.
pip3 install -r requirements.txt
GUI is optional and requires extra modules to run with GUI. To install the modules required to run GUI, run the following command
pip3 install -r requirements-gui.txt
nsz.py --help
usage: nsz.py [-h] [-C] [-D] [-l LEVEL] [-B] [-S] [-s BS] [-V] [-p]
[-t THREADS] [-m MULTI] [-o [OUTPUT]] [-w] [-r] [--rm-source]
[-i] [--depth DEPTH] [-x] [--extractregex EXTRACTREGEX]
[--titlekeys] [-c CREATE]
[file [file ...]]
positional arguments:
file
optional arguments:
-h, --help show this help message and exit
-C Compress NSP/XCI
-D Decompress NSZ/XCZ/NCZ
-l LEVEL, --level LEVEL
Compression Level: Trade-off between compression speed
and compression ratio. Default: 18, Max: 22
-B, --block Use block compression option. This mode allows highly
multi-threaded compression/decompression with random
read access allowing compressed games to be played
without decompression in the future however this comes
with a slightly lower compression ratio cost. This is
the default option for XCZ.
-S, --solid Use solid compression option. Slightly higher
compression ratio but won't allow for random read
access. File compressed this way will never be
mountable (have to be installed or decompressed first
to run). This is the default option for NSZ.
-s BS, --bs BS Block Size for random read access 2^x while x between
14 and 32. Default: 20 => 1 MB
-V, --verify Verifies files after compression raising an unhandled
exception on hash mismatch and verify existing NSP and
NSZ files when given as parameter
-p, --parseCnmt Extract TitleId/Version from Cnmt if this information
cannot be obtained from the filename. Required for
skipping/overwriting existing files and --rm-old-
version to work properly if some not every file is
named properly. Supported filenames:
*TitleID*[vVersion]*
-t THREADS, --threads THREADS
Number of threads to compress with. Numbers < 1
corresponds to the number of logical CPU cores for
block compression and 3 for solid compression
-m MULTI, --multi MULTI
Executes multiple compression tasks in parallel. Take
a look at available RAM especially if compression
level is over 18.
-o [OUTPUT], --output [OUTPUT]
Directory to save the output NSZ files
-w, --overwrite Continues even if there already is a file with the
same name or title id inside the output directory
-r, --rm-old-version Removes older versions if found
--rm-source Deletes source file/s after compressing/decompressing.
It's recommended to only use this in combination with
--verify
-i, --info Show info about title or file
--depth DEPTH Max depth for file info and extraction
-x, --extract Extract a NSP/XCI/NSZ/XCZ/NSPZ
--extractregex EXTRACTREGEX
Regex specifying which files inside the container
should be extracted. Excample: "^.*\.(cert|tik)$"
--titlekeys Extracts titlekeys from your NSP/NSZ files and adds
missing keys to ./titlekeys.txt and JSON files inside
./titledb/ (obtainable from
https://github.com/blawar/titledb). Titlekeys can be
used to unlock updates using NUT OG (OG fork
obtainable from https://github.com/plato79/nut). There
is currently no publicly known way of optioning NSX
files. To MitM: Apply disable_ca_verification &
disable_browser_ca_verification patches, use your
device's nx_tls_client_cert.pfx (Password: switch,
Install to OS and import for Fiddler or import into
Charles/OWASP ZAP). Use it for aauth-
lp1.ndas.srv.nintendo.net:443, dauth-
lp1.ndas.srv.nintendo.net:443 and
app-b01-lp1.npns.srv.nintendo.net:443. Try with your
WiiU first as there you won't get banned if you mess
up.
-c CREATE, --create CREATE
create / pack a NSP
- To compress all files in a folder:
nsz -C /path/to/folder/with/roms/ - To compress all files in a folder and verifying signature of compressed files:
nsz --verify -C /path/to/folder/with/roms/ - To compress all files in a folder with 8 threads and outputting resulting files to a new directory:
nsz --threads 8 --output /path/to/out/dir/ -C /path/to/folder/with/roms/ - To compress all files in a folder with level 22 compression level:
nsz --level 22 -C /path/to/folder/with/roms/ - To decompress all files in a folder:
nsz -D /path/to/folder/with/roms/
To view all the possible flags and a description on what each flag, check the Usage section.
NSZ files are not a real format, they are functionally identical to NSP files. Their sole purpose to alert the user that it contains compressed NCZ files. NCZ files can be mixed with NCA files in the same container.
NSC_Builder supports compressing NSP to NSZ, and decompressing NSZ to NSP. The sample scripts located here are just examples of how the format works.
NSC_Builder can be downloaded at https://github.com/julesontheroad/NSC_BUILDER
XCZ files are not a real format, they are functionally identical to XCI files. Their sole purpose to alert the user that it contains compressed NCZ files. NCZ files can be mixed with NCA files in the same container.
These are compressed NCA files. The NCA's are decrypted, and then compressed using zStandard. Only NCA's with a 0x4000 byte header are supported (CNMT nca's are not supported).
The first 0x4000 bytes of a NCZ file is exactly the same as the original NCA (and still encrypted).
At 0x4000, there is the variable sized NCZ Header. It contains a list of sections which tell the decompressor how to re-encrypt the NCA data after decompression. It can also contain an optional block compression header allowing random read access.
All of the information in the header can be derived from the original NCA + Ticket, however it is provided preparsed to make decompression as easy as possible for third parties.
Directly after the NCZ header, the zStandard stream begins and ends at EOF. The stream is decompressed to offset 0x4000. If block compression is used the stream is splatted into independent blocks and can be decompressed as shown in https://github.com/nicoboss/nsz/blob/master/nsz/BlockDecompressorReader.py
class Section:
def __init__(self, f):
self.magic = f.read(8) # b'NCZSECTN'
self.offset = f.readInt64()
self.size = f.readInt64()
self.cryptoType = f.readInt64()
f.readInt64() # padding
self.cryptoKey = f.read(16)
self.cryptoCounter = f.read(16)
class Block:
def __init__(self, f):
self.magic = f.read(8) # b'NCZBLOCK'
self.version = f.readInt8()
self.type = f.readInt8()
self.unused = f.readInt8()
self.blockSizeExponent = f.readInt8()
self.numberOfBlocks = f.readInt32()
self.decompressedSize = f.readInt64()
self.compressedBlockSizeList = []
for i in range(self.numberOfBlocks):
self.compressedBlockSizeList.append(f.readInt32())
nspf.seek(0x4000)
sectionCount = nspf.readInt64()
for i in range(sectionCount):
sections.append(Section(nspf))
if blockCompression:
BlockHeader = Block(nspf)NSZ pip package: https://pypi.org/project/nsz/
Forum thread: https://gbatemp.net/threads/nsz-homebrew-compatible-nsp-xci-compressor-decompressor.550556/
SciresM for his hardware crypto functions; the blazing install speeds (50 MB/sec +) achieved here would not be possible without this.