CRC32 Programs

A few things about the CRC32 Calculator

The program calculates the 32-bit Cyclic Redundency Check (CRC) of a given file. For a complete description of what that is, check the mathematical review. This is a completely re-written new version!

It comes at three (yes I added one!) versions, all for windows (tested with Win98). The command-line version is quite small and delicate, you can just type "crc32" to see the instructions. The CheckCRC is the "windows" version, and it is capable of adding a "crc32" feature in the right-click menu. The new version is quite powerfull. It's a command-line pipe that calculates the crc32 of its standard input.

These programs are created with Delphi 6.

The Windows based program: CheckCRC

Download the zip file CheckCRC.zip Filesize: 216 KB

Extract the file, then run CheckCRC.exe. You will also find install.txt and readme.txt.

The program will add a selection (CRC32) to the popup menu when you right-click any file. To remove this go to Control Panel -> Add/Remove Programs -> CRC32 Calculator. You must delete the file manually to completely remove the program from your system.

A window will come up with a button (Select File). Click on the button and open the file you want. A progress indicator will show up if the file is large and the CRC32 will appear.


Program screenshot

When you use the right-click menu command the same window will come up, but the CRC32 of the selected file will be already calculated.

The Command Line Version: Crc32

Usage:

  • CRC32 [/?]
  • CRC32 filename [/F /H /S /D /Bxxxx /R]

Wildcards are allowed (like *.*, etc)

Options:

  • /F to display full filename
  • /H to include hidden files
  • /S to include system files
  • /D to scan subdirectories
  • /Bxxxx to set the buffer size in Kbytes - Default = 1024
  • /R to supress progress report
  • /? to display help screen

Parameters may stack (you can type /fhsdrb1024 and it will be accepted)

You may wish to increase buffer size if dealing with *large* files, do not however use a larger buffer than the physical memory. The minimum value is 1 KB = 1024 bytes, the default is 1 MB. Depending on the system, the available RAM and the file size different values may have quicker results. If the file is larger than the buffer you will also see a progress indicator.

The result will be something like: "filename - CRC32: $xxxxxxxx" or, if you use wildcards (as *.*) a list of the files and their CRCs. Note that the procedure may take time for large (or many) files, so using a command like: crc32 *.* /d in the root directory may *take a while*.

The great thing about command-line is that using the " >filename" parameter you pass the results to the file. So a "crc32 *.* /fhsdr >result.txt" will create a quite flexible result list.

You may download the command-line version here: crc32.zip (28 KB)

The Command-line Pipe version: Crcp

This is a command-line program that calculates the crc32 of its standard input and then writes it out (to its standard output) in hex format.

Usage:

  • {command} | crcp
  • crcp < {filename}

Just typing crcp leads to error. Note that is doesn't take filename as a parameter! You MUST use input redirection "<"!

Yes, you can download it! Here 11KB

Hack CRC32 command-line

This program analyzes a file, calculates its CRC32 and then calculates what modification needs to be done (actually, addition to the end of the file up to 4 bytes) so that the file's new CRC matches a given CRC.

The method is quite brute, but it seems that a few minutes are needed and there's no need for a more sofisticated method. However, a stronger version could alter 4 specific bytes so that the file size isn't changed. This is to show that CRC32 is NOT safe for security checks.

Usage: crch {filename} {crc}

Where crc is desired crc32 in hex format (8 digits).

In a few minutes (depending on your machine and your luck) 4 or less bytes will be added to the file. Usually, this will not affect the file in any other way (ie, executables will run, images will show up, etc), but check it out to be sure.

Don't mess it up entering files that don't exist for fun. I haven't done any error checking.

Crch.zip 26 KB. Use at your own risk...

Hack CRC32 windows version

As previous, this program analyzes a file, calculates its CRC32 and then calculates what modification needs to be done (actually, addition to the end of the file up to 4 bytes) so that the file's new CRC matches a given CRC.

1.Click Select to select the file, or just type in the filename.

Optional: Click Examine to see the crc32 of the file. This will be done anyway later so if you have a large file don't do it.

2.Enter requested CRC32 in hex format (8 digits).

3.Click on Do It!

A few minutes later, a dialog will appear and your permission is required to append the necessairy bytes to the file. Usually, this will not affect the file in any other way (ie, executables will run, images will show up, etc), but check it out to be sure.

Don't mess it up entering files that don't exist for fun. I haven't done any error checking. (Didn't I say that before?)

Crch.zip 216 KB. Use at your own... risk? Yep, that's it.

CRC32 Source

Total downloads!

  • Windows CRC32 Calculator 1.1.0.3: CheckCRC.zip 216 KB
  • Command-line version CRC32 Calculator 1.11: crc32.zip 28 KB
  • Command-line pipe CRC32 Calculator: crcp.zip 11KB
  • Command-line CRC32 Hacker: Crch.zip 26 KB.
  • Windows version CRC32 Hacker: Crch.zip 216 KB.
Last modified:
This page has been viewed 222488 times since 16/9/2003.