Sparanoid

Media Auto Hash Rename will rename any file (specific files can be ignored by file extension) during upload, with unique, low collision hashes. Hash characters and length can be configured for even lower collision rate.
More information please visit my <a href="https://sparanoid.com/work/media-auto-hash-rename/" rel="nofollow ugc">site</a>.
This plugin provides no configuration GUI to make it more easier to maintain with the future WordPress updates.
Currently there’re 3 constants you can configure in your <code>wp-config.php</code>, I recommend WP-CLI for maintaining these constants.
<ul>
<li><code>MAHR_LENGTH</code>: length of the random hashes, (default to <code>8</code>), longer can help reduce collision. Hashes at the length of 8 can be collision-free at the scale of 50,000 images).</li>
<li><code>MAHR_CHARS</code>: Characters used in hashes, default to <code>0123456789abcdefghijklmnopqrstuvwxyz_</code>, You can add more characters like uppercased alphabelts to dramatically reduce the collision without increasing the length of your filenames. But please note that this option can be dangerous if you’re not familer with general URI encoding. So if you don’t know what characters are allowed in a filename, just keep it untouched and use the default option.</li>
<li><code>MAHR_IGNORE</code>: File extensions to be ignored, default to <code>pdf, zip</code>, you can define a comma delimited list of file extensions to bypass renaming process of this plugin. All files that has the file extension you defined in the list will be ignored. Please note that:
<ul>
<li>File extensions must be defined without the leading peroid, for example: <code>'pdf, 7z, bmp'</code> works, <code>'.pdf, .7z, .bmp'</code> does not.</li>
<li>With (<code>'pdf, zip'</code>) or without (<code>'pdf,zip'</code>) space both work.</li>
<li>If you define your own ignore list, default ignore list will be discarded. For example, if you define <code>'7z'</code>, then <code>'pdf, zip'</code> will be processed during upload. You need to reapply these extensions with your own: <code>'7z, pdf, zip'</code>.</li>
<li>If you don’t need to ignore any files by its extension. define an empty array <code>[]</code> (without quotes) to this option: <code>define( 'MAR_IGNORE', [] );</code> to force process PDF and ZIP files.</li>
</ul>
</li>
</ul>

Media Auto Hash Rename

Rename media filename during upload with unique hash.

Jason Coleman

Adds a short code like [download file=”path_to_file”] that embeds a form in the post asking for an email address before showing a link to a file for download. Great for promoting white papers and other digital assets on your site.
Live demo: http://www.strangerstudios.com/blog/2010/07/ss-downloads-wordpress-plugin/
The plugin works in 3 parts.
<ol>
<li>
The short code to add the form to your pages.
</li>
<li>
The logic to check (using session variables) if the user has provided an email address before showing either the email capture form or the download link.
</li>
<li>
A script to serve files securely. It checks for the same session variable before delivering the file. Files can be located outside the web directory or servered from the uploads folder, etc, with an obfuscated URL.
</li>
</ol>
The look of the email and download forms can be changed by copying files from the /css/ and /templates/ folder of the plugin into your active theme folder. Rename the files ssd-original_file_name.php/css (e.g. ssd-download.php or ssd-ss-downloads.css) and edit as needed.

SS Downloads

Embed forms in your pages and posts that accept an email address in exchange for a file download.

Media Auto Hash Rename vs SS Downloads