SHA-256 Checksums Explained

An SHA-256 checksum is a sequence of numbers and letters that you can use to check that your copy of a downloaded update file is identical to the original.

Small changes in a file produce very different looking checksums. A single character difference produces a very different looking checksum. You can use checksums to check files and other data for errors that occur during transmission or storage. For example, a file might not have properly downloaded due to network issues. You can also use a checksum to help verify that an attacker has not made changes to a file.

If you know the checksum of the original file, you can run a checksum or hashing utility on it. If the resulting checksum matches, you know the file you have is identical.

How to calculate SHA-256 checksums

You can use Windows Powershell to calculate the SHA-256 checksum for a file.

Open Windows Powershell.
To do this, type Powershell in the Windows Start menu command box.
Type Get-FileHash followed by a space.
Drag the downloaded ZIP file onto the Windows Powershell window after the Get-FileHash command.
This inserts the path after the command, to look similar to the following screen text:
```
PS C:\Users\UserName> Get-fileHash C:\Users\UserName\Downloads\cdq2019s14_Windows.zip
```

Press Enter.

This results in output similar to the following:

PS C:\Users\UserName> Get-FileHash C:\Users\UserName\Downloads\cdq20191s14_Windows.zip

Algorithm       Hash                                                                   Path
---------       ----                                                                   ----
SHA256          BD94760347BABBB0B12ADFEB41FF01B90DD7F4C16F9B6C2088CD2526F6223898       C:\Users\UserName\Downloads\cd...

Compare the calculated hash value with the original hash value.

You should not have to look too closely, as there will be a massive difference in the checksum even if there is only a tiny difference in the underlying file.