REV: 20190625 Self-Extracting Encrypted File Creator
MakeSDF is currently in early development.
The version you see here is a working release but does not contain features under development.
If you would like to participate in the testing and/or have comments or suggestions please contact us at
MakeSDF: Create a Self-Decrypting HTML file of any text.
- Provided by Netwindow Solutions and HT Consulting

Exactly what does MakeSDF Do?
MakeSDF takes your text data, encrypts it using a 256 bit key and Advanced Encryption Standard (AES) to create a Self-Decrypting HTML file (SDF) that can be loaded into any browser in order to decrypt and view the original content. In addition to your encrypted data, the SDF contains the decryption program itself.

Your data will be encrypted/decrypted using a key phrase that you provide. The encryption method used is one of the best encryption techniques available. If you lose the key you will never be able to decrypt your data.

Both makeSDF.html and the SDF itself are standalone HTML pages that can be saved on your PC, laptop, mobile device, flash drive, uploaded to the Internet, or sent as an email attachment. You or the recipient need simply load the .html file into a browser. The SDF key itself, perhaps sent separately or in some cases (not generally recommended) included in the email that had the SDF attachment.

When loaded the SDF will ask for the key and use it to decrypt and display the original data.

None of your data ever leaves your device during the Encryption or Decryption processes.
Both makeSDF and the SDF are self-contained and use no Internet connection. In both makeSDF and the SDF the Encryption and Decryption processes all take place on your device.

This will allow you to build your own unlimited database of Self-Decrypting files containing information that never leaves your computer.

If you wish, you may save a copy of makeSDF.html on your own device and at any time later just load it from your device even while offline using your browsers File/Open menu. To save your own copy of makeSDF.html click/tap below:

Save a copy of makeSDF.html on your local system.

If you do save your own copy of makeSDF.html, we recommend that you occasionally revisit the website to check for updated versions and additional encryption products and information.

What things can MakeSDF Encrypt?

The simple answer is any and all text. The current release of MakeSDF will convert any and all and ONLY plain text. At this time images, graphics, various fonts, faces, bolding or colors will not be maintained. As an example, the HTML of a web page can be encrypted perfectly, but copying/pasting the browser display of a page into MakeSDF would only encrypt the text portions of that page.

Although you can encrypt/decrypt the the HTML itself perfectly, loading that page into your browser can be unpredictable unless you are loading it from the original host location since the HTML may be calling for resources that are located on its native host and depending upon how those were coded in the HTML they may now fail.

Select the source of the textual data that you wish to encrypt

Choose an encryption key or phrase and enter it below
You MUST know the Encryption Key/s you use here to later Decrypt the data. There is NO RECOVERY other than guessing.

Retype the key to verify.

OPTIONAL: Double Encryption - Use a second layer of encryption
Is Double Encryption effective?
Yes, No, and Maybe.
First of all, single encryption with a wise choice of key is all the protection you are likely to ever need. The question of double encryption is a bit debatable. If you are trying to shield against the most powerful computers and government agencies it makes little if any difference, but you probably would not be using this tool if that is the case. If you are concerned with attacks less powerful, such as a "library" attack of common single words pr phrases then a reasonable choice of two keys doing two layers can be very effective protection. It also might be easier to remember a pair of somewhat simpler, but not related, keys than one complex one.

When using two layers the SDF screen presented to the user will display two blank input boxes instead of one and the user must enter the keys in the same order that you have entered them here with the FIRST/(inner) KEY in the top field and the SECOND/(outer) KEY in the lower field. For the decryption process the the Keys will be applied in the reversed sequence.

Choose a second (outer) encryption key or phrase and enter it below:

Retype the second key to verify.

OPTIONAL: Provide a visible "Hint"

If you choose to do so you may provide a "hint" to your encryption Password that would have some meaning to you but not to anyone else. If given, the Hint will be visible above the Password solicitation in the Self-Decryptor.

OPTIONAL: "Dark Mode Key"

Dark Mode will display an initial totally blank screen when the Self-Decrypting .html file is loaded into the browser.
In order to continue the user must:
  • Tap/click the blank screen
  • Enter the Dark Mode Key that you provide here and then
  • Tap/click on the display window to reach the SDF process.

  • Dark Mode is not a significant security feature and can be easily defeated. However, it is included to discourage "curiosity" about the Self-Decryptor page. To activate Dark Mode, enter something very simple that you yourself will not forget (like your own name or "go"). You may not want to use this option if you are sharing your SDF with others who might forget the Dark Mode Key.

    3 Build the Self-Decrypting File

    4 Save the Self-Decrypting File

    You or anyone you provide the SDF to may load it into a browser using the browser "File" menu or corresponding action and decode it at any time. You may upload the SDF to the Internet, attach it in an email to yourself or others. or choose any method you wish to make it available. All that is required is the SDF file, a browser, the decryption key/s and any option instructions. The SDF file is a stand-alone file containing both the encrypted data and the decrypting program running on your device and does not need Internet access.
    Self Decryptor

    The sections below this point are informational or options.
    No action is required after the save in 4 above.

    This is your Encrypted Original Data Only
    In addition to the self-extracting file above, below is the encrypted original content only.

    Encrypted Text

    The Decryption of your Encrypted Original data
    The window below is a test decryption of your message content and should match it perfectly.
    Decrypted Text