- Cyclic Redundancy Check (CRC) and Secure Hashing Algorithm (SHA) are integrity-checker and encrypting algorithms, respectively, that appear in the context menu after installing 7-Zip.
- To remove this option, go to 7-Zip File Manager, click Tools, then click Options. Switch to the 7-Zip tab and uncheck the “CRC SHA” and “7-Zip- > CRC SHA >” options.
There have been reports across various forums of people seeing a new entry in the Windows contextual menu with the tag “CRC SHA.” This becomes visible after installing 7-Zip – a file-archiving software. This is normally used to save space on the disk by compressing files and folders, for sharing the compressed items over the internet, and to decompress files usually downloaded from the internet.
However, now 7-Zip also offers a checksum algorithm. A checksum is a method to check for any errors or damages to a file that has been transferred from one place to another. For example, if you are receiving a file from another device over the internet, the checksum algorithm will check for errors, and verify its integrity by comparing the contents of the file received and the file that was initially sent.
Upon expanding the “CRC SHA” option in the Windows context menu, you may see additional options, which are as follows:
This guide informs you on what the CRC SHA entry is, and what the sub-entries are used for. Additionally, if you do not need this option, this post also provides a method to remove it.
Table of Contents
What is Cyclic Redundancy Check (CRC)
The Cyclic Redundancy Check is an error-detecting mechanism used in digital networks to identify alterations to digital data, whether accidental or intentional. Bit errors, where the zeros change to ones and the ones change to zeros, may arise in transferred data as a result of external interference or issues with the transmission channel. To address this issue, the data is checked for errors at the receiving end before being accepted.
Using a specific algorithm, the transmitting end generates a check code for the data and forwards it to the receiving end along with a “check code”. To check whether the data has changed during its transit, the recipient end performs the same computation to get the same results.
The algorithm that the CRC mechanism uses is based on binary division. The end of the data unit has a series of redundant bits, known as “cyclic redundancy check bits”, which are appended to it to make the final data unit accurately divisible by a second, predefined binary number, known as the divisor. The process is carried out until the remainder is zero.
What is Secure Hashing Algorithm (SHA)
As the name implies, SHA is a mathematical hashing algorithm that takes an input and produces a complex, fixed-sized output of characters. These characters are very different from the input, not only in length, since they have been encrypted.
The purpose of SHA is to encrypt the original data using a private key, and only that particular key can unlock (decrypt) the complex string of characters and revert it to the original message.
SHA has different versions, which means that their encrypting algorithms are of different standards, and generate different lengths of complex characters. The longer the string, the more secure the data. This is why you may see SHA-1 and SHA-256 in the context menu after installing 7-Zip.
SHA-1 is a quick and straightforward encryption method that has been demonstrated to be susceptible to cyber-attacks. In contrast, SHA-256 is a more recent and safe algorithm that generates a bigger string, thus making it more secure, which makes it perfect for crucial applications where security is of utmost importance.
What are CRC-32, CRC-64, SHA-1, SHA-256 options in Windows context menu?
If you right-click a file on Windows after installing 7-Zip, if you expand the “7-Zip” option, and then expand the “CRC SHA” option, you will find more CRC and SHA options inside, along with the asterisk (*) option.
Clicking on these options opens a window where the respective algorithm shows you the out. Clicking CRC-32 will execute the CRC algorithm and show the 32-bit output result. Similarly, clicking the SHA-256 option will output the 256-bit SHA algorithm. The same is true for the remaining options. Clicking the asterisk shows all outputs.
How to remove CRC SHA from Windows context menu
Although the CRC SHA options can help verify the integrity of any file on Windows, not everyone wants this additional option in the contextual menu. Thankfully, there is a method to remove it without uninstalling 7-Zip. Here is how:
Search for the “7-Zip File Manager” application in the Start menu and open it.
Click Tools from the ribbon menu and then click Options.
Switch to the “7-Zip” tab.
Uncheck the following options in the “Context menu items” section:
- CRC SHA
- 7-Zip > CRC SHA >
Click Apply and OK.
Performing the steps above will remove the CRC SHA option from the Windows context menu as well as the 7-Zip submenu.
In case you want to bring back both or one of these options, all you need to do is check the respective option(s) again from the 7-Zip File Manager’s settings.
The added CRC SHA option in the context menu after installing 7-Zip is a useful utility to have, only if you know how to use it. For the sysadmins and the cyber-security experts, this option might be of some use. However, for the average home user, the CRC SHA option may be a nuisance, and clicking it accidentally would only be frustrating.
This is why this article provides a method to remove the option and still keep on using the 7-Zip archiver and compressor.