UK Secure File Transfer - Virtual Data Rooms

« Back

File Integrity Checking

How to generate a SHA512 hash on a file in Mac OS and Windows

Data Send UK Ltd does not provide or display cryptographic file hashes (like MD5 or SHA-256, SHA512) on its download page as this would defeat the purpose of file integrity checking becasue Data Send is in the middle. All files are transfered byte-for-byte during the upload process, which means it is always an exact copy of the original source file. However, to take advantage of file integrity checking where it is needed to meet compliance, the sender ( data "controller") must create the hash in the first instance for the original source file they have. Once the hash is created, it can then be sent directly to the desired recipient by some other means. The recipient must also be informed on what Algorithm has been used to create the hash, so they can use the same Algorithm when verifying the file. The recipient can then use this hash to verify it against the file they have downloaded from the Data Send UK service. In some scenarios the recipient may also need to prove to another party that 'they have not modified the file' in any way either... and so on it goes....

SHA512 hashes are a great way to create a unique signature for a file, so that you can be sure it is the same and unaltered.

The way a hash is calculated means that even a very small change (e.g. just changing a space or one character) will result in a radically different hash; so it is very clear that the file has been altered when hashes are compared. The chance of two files having the same hash is astronomically improbable.

Changing the actual filename does not have any impact on the hash verification. Hash functions calculate the unique code using only the actual data inside the file, not the system labels or folder paths.

You can use SHA512 hashes to create a unique signature for files whenever you supply data, as this in conjunction with a verified digitally signed manifest, is a great way to track and verify that a file is exactly the same and has not been altered.

Mac OS - How to generate a SHA512 hash on a file

Open a command line / terminal and type:

shasum -a 512 followed by a space

Drag and drop your file directly into the Terminal window to automatically paste the exact file path.

e.g. shasum -a 512 /path/to/yourfile.iso

To check a file hash you have received against the file you have downloaded

It is the same procedure as above - only the path to the file will be the path to your downloaded file. Compare the displayed hash against the hash you have received.

--------------------

Windows - How to generate a SHA512 hash on a file

Right-click the Windows Start button and select Terminal (or PowerShell). Then Type:

Get-FileHash followed by a space.

Drag and drop your file directly from File Explorer into the Terminal window to automatically paste the exact file path.

You need to add the correct Algorithm you want to use. In this tutorial we have used SHA512 so add, -Algorithm SHA512

You will then have something like this example string: -
Get-FileHash "C:\path\to\file.exe" -Algorithm SHA512

Press Enter. The SHA512 hash will be displayed.

To check a file hash you have received against the file you have downloaded

It is the same procedure as above - only the path to the file should be the path to your downloaded file instead. Compare the displayed hash against the hash you have received.