Introduction: What is a checksum value and why is it useful to us?
A checksum is a small-sized block of data derived from another block of data. They are used to ensure that a copy of a block of data is unchanged from its original. They are useful in verifying files that you have downloaded contain exactly what was intended. For example, when using a download mirror to get install files from a known vendor. Having a checksum value provided by the vendor allows you to compare it with the value of the file you have downloaded to ensure it is a perfect copy.
For this explanation, I will use VirtualBox and SHA-256
*Please note, not all websites will provide checksums to verify downloads. Always ensure checksum value is provided from a trusted source.
1. Navigate to the download page of your chosen program. For example, I have navigated to https://www.virtualbox.org/wiki/Downloads
2. Download your desired file and locate the checksum value table. Below is the SHA-256 checksum values for the differing releases of VirtualBox. Locate the relevant value for your download and save it in a text file for easy comparison.
3. Right-click the downloaded file, select more options to expand the menu, locate CRC SHA and select your desired algorithm in this case I have selected SHA-256.
4. This will cause a program to perform a hash function and provide you with a value for the file.
5. Copy the resulting checksum below the original value and compare them If they match perfectly this means the file you have downloaded is an unaltered copy of the original upload. Note Capitalisation is not important, so long as the characters match perfectly.