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User Guide

Downloading Media

Downloading Media

What is Media

In the most basic terms, media is an alternate word for file. On the web, media refers to a specific group or type of file. These types are: audio, document, image, and video.

Downloading or Viewing

Downloading and viewing a file is commonly misunderstood as being two different concepts. To view a file, it must be first downloaded. To download a file, the proper path must be used. On many websites, this is a static (non-changing) URL. On this website, the URL is dynamic.

Table of files showing the URL path
Downloading Media - Image 1.1

Dynamic URL

The URL is designed to be reasonably short. There are four primary parameters (aka: parts). The first is the letter f, which stands for file and is used to prevent or reduce URL path conflicts. The second is the letter c, which stands for checksum. The third is a unique id shorthand consisting of 8 hexadecimal digits. The fourth is the (dynamic) filename.

The second parameter defines what the next parameters are, how they get processed, and the type of file that is returned. To download a file, a value of c is used. In this case, the immediate next parameter will be the unique checksum for the file. The fourth, and final, parameter is optional. Just about anything may be specified for this parameter. The name supplied here will be the name the file is returned as.

Lets say you had a file called image-downloading_media-1.1.png.
That file has a short checksum of 4668c5cf.
If you wanted to send an e-mail with the shortest possible URL, then you would use the following:
Maybe you did not like the file being called image-downloading_media-1.1.png.
To use a more convenient name, add a fourth parameter using whatever words you wish to.
For example, to use a name of Download Media Screenshot.png the URL would look like:
/f/c/4668c5cf/Download Media Screenshot.png.
This allows for multiple users to choose their own naming convention at any point in time without having to make any changes to the file.

Validating Download

Not only are you able to download the file using the dynamic url, you can also download a full checksum to validate the contents of the download. Checksums are sequences of hexadecimal digits that uniquely identify some file. When a file is downloaded, you can compare the checksum you get with the checksum of the file to ensure that the file is, in fact, the file that you thought you downloaded.

To get the checksum, replace the c from the dynamic url with the letter s. Thats it.

The constructed URL functions in the same way as the c download method, except that the checksum is returned and has an extension of .sha256sum appended to the name.
To get the checksum file of the file mentioned in the previous example, the constructured URL would look like:
For the second part of that example, the would look like:
/f/c/4668c5cf/Download Media Screenshot.png.
In the first case, the downloaded file would be:
image-downloading_media-1.1.png.sha256sum (or 4668c5cf.sha256sum if the browser does not follow certain standards).
In the second case, the downloaded file would be:
Download Media Screenshot.png.sha256sum.

Now that the checksum file is downloaded, it needs to be used to validate the file it represent (make sure that the file to be validated is downloaded as well). There are different tools out there to validate a file using its checksum.

The standard tool for verifying a sha256 checksum is the command-line program sha256sum.
The sha256sum tool is simple and straight-forward.
Specify the checksum name with the appropriate argument:
sha256sum -c image-downloading_media-1.1.png.sha256sum.